Dissertations / Theses on the topic 'Ecologic variability'

Les communautés microbiennes benthiques participent activement au recyclage de la matière organique et de fait au fonctionnement biogéochimique des écosystèmes lacustres. Ces communautés comportent de nombreux phyla mais leur diversité fonctionnelle est encore incomplètement connue. Ce travail vise à appréhender les modifications de structure et d'abondance des gènes fonctionnels en lien avec la distribution spatiale verticale (liée au gradient d'oxydoréduction), la variabilité spatiale horizontale (zone côtière vs pélagique) et la dynamique saisonnière liée au brassage de la colonne d'eau (ré-oxygénation des interfaces benthiques), de même que l'identification de la diversité des méthanotrophes et des méthanogènes.Pour cette étude, des carottes sédimentaires ont été prélevées sur un transect zone côtière – zone pélagique, à différentes dates au cours d'un cycle annuel. Chaque carotte sédimentaire a été analysée dans la verticalité entre l'interface eau-sédiment et 20 cm. Les communautés microbiennes participant au cycle du méthane ont été ciblées par 2 gènes de fonction et étudiées en termes de structure, de diversité et d'abondance; par ailleurs, des marqueurs phylogénétiques ont été utilisés pour caractériser les communautés bactériennes et archéennes totales.Les résultats de l'étude spatiale montrent que, si à l'échelle locale (station d'échantillonnage) une relative homogénéité des communautés microbiennes (totales et fonctionnelles) est observée, des variabilités fortes sont détectées d'une part à l'échelle des transects horizontaux en lien avec des changements de conditions environnementales et d'autre part dans la verticalité des sédiments sous l'effet des conditions d'oxydoréduction. La communauté bactérienne étant la plus affectée dans la verticalité, avec des changements de structure entre toutes les strates étudiées. Dans cette même étude, une analyse comparative de la structure des communautés (totales et fonctionelles) a démontré que l'analyse d'échantillons individuels permettait d'obtenir un plus grand nombre d'OTU que l'analyse des mêmes échantillons regroupés en pools.Les résultats de l'étude de la dynamique temporelle des communautés méthanogènes et méthanotrophes révèlent des changements de structure et abondance, principalement à l'interface eau - sédiment en lien avec la dynamique d'oxygénation du lac. Quant à l'analyse de la diversité, elle montre une dominance des Methanomicrobiales (Methanoregula principalement) pour les méthanogènes, mais les Methanosarcinales (Methanosarcina) et les Methanobacteriales (Methanobacterium) ont également été identifiés. Pour les méthanotrophes, la diversité est dominée par Methylobacter en zone profonde et par Methylococcus en zone côtière, les méthanotrophes de Type II (Methylosinus et Methylocystis) ont aussi été identifiés.L'ensemble de ces travaux souligne l'importance de prendre en compte, à la fois la variabilité spatiale (horizontale et verticale) et la variabilité temporelle, des communautés méthanogènes et méthanotrophes lors de l'étude de ces communautés. Les changements quant à leurs structures et leurs abondances sont des paramètres non négligeables pour comprendre les processus impliqués dans le cycle du méthane
Benthic microbial communities are actively involved in organic matter recycling and fact biogeochemical functioning of lake ecosystems. These communities comprise many phyla but their functional diversity is still incompletely known. This study is focused on the benthic microbial communities involved in the methane cycle in lacsutrine suystems. We aimed understanding the structural and abundance changes of functional genes related to the vertical distribution (redox gradient in sediment), the horizontal variability (coastal vs. pelagic benthic zone) and seasonal dynamics related to mixing of the water column (re-oxygenation of benthic interface). The composition of methanotrophic and methanogenic communities was characterized by sequencing analyses.For this study, sedimentary cores were sampled along a transect from coastal to pelagic zone, at different times during an annual cycle. In addition, each sediment core was analyzed in its verticality from the water-sediment interface to 20 cm depth. Microbial communities involved in the cycle of methane (methanogenesis and methanotrophy) were targeted by 2 functional genes (mcrA and pmoA). Furthermore, phylogenetic markers were used to characterize the total bacterial and archaeal communities. These communities are studied in terms of structure (genotyping), diversity (sequencing) and abundance (qPCR, DNA) of their functional genes.The results of the study showed that, on a spatial scale, a low heterogeneity was detected for a given sampling station in terms of structure of microbial communities (total and functional), however, a high variability was detected both at an horizontal scale along a transect (costal vs. pelagic zone), due to contrasted environmental conditions, and at a vertical scale (upper to deeper layers in the core) under the effect of redox conditions. The bacterial community being the most affected in the verticality, with structural changes among all strata studied. In the same study, a comparative analysis of the structure (for all of the communities), between pooled samples and individual samples, demonstrated that the analysis of individual samples provided a greater number of OTU for the majority of microbial communities.Moreover the study of the temporal dynamic of methanogen and methanotroph communities revealed changes in the structure and abundance, mainly at the water - sediment interface, according to the oxygenation levels that varied through time. The analysis of diversity showed a dominance of Methanomicrobiales (Methanoregula mainly) for methanogens, but Methanosarcinales (Methanosarcina) and Methanobacteriales (Methanobacterium) were also identified. The methanotrophs' community was dominated by Methylobacter on deeper stations and by Methylococcus in coastal station. Type II methanotrophs (Methylosinus and Methylocystis) were also identified.This work highlights the importance of taking into account both the spatial variability (horizontal and vertical) and the temporal variability of methanogen and methanotroph communities. Changes on their structures and abundances are significant parameters for understanding the processes involved in the methane cycle

Seabirds have evolved within an open and dynamic environment, the ocean. As meso-top predators, seabirds are greatly influenced by the oceanographic conditions driving marine productivity, and therefore, distribution of their prey. Consequently, seabirds’ behaviour and, ultimately, life-history traits are greatly influenced, by the ever-changing oceanographic conditions. However, oceanographic conditions are currently changing at ever-increasing rates due to global warming and human harvest impacting marine ecosystems. Thus, seabirds have become particularly vulnerable to these changes. Accordingly, in this thesis, we investigated the ecological responses of seabirds, in terms of foraging and breeding performance, to the spatio-temporal variability of environmental conditions imposed by oceans and exacerbated by climate and human stressors. In particular, we (i) identified the climate and human stressors impacting the world’s ocean, (ii) investigated the actual scale at which seabirds interact with their environment, (iii) assessed how seabirds respond to oceanographic variability by changing their foraging and reproductive strategies and (iv) proposed an integrative tool for the design of marine reserves protecting seabirds and their environment. The objectives of this thesis were accomplished through advanced procedures in the fields of satellite remote sensing and animal tracking. Our results confirmed the unprecedented changes experienced by oceans in the last decades. However, we were able to provide deepest insights on the uneven distribution of climate and human driven environmental changes. When investigating the link between such environmental variability and seabirds’ behaviour, we found that dynamic processes as ocean currents were key factors determining the scale at which seabirds interact with their environment. Environmental features driving the spatiotemporal distribution of prey (e.g. sea surface temperature, chlorophyll-a, sea fronts and persistent areas of productivity) along with industrial fisheries played a fundamental role in determining the foraging distribution of seabirds. However, seabirds’ foraging strategies were largely constrained by limitations imposed by their central-place foraging behaviour and by dynamic factors such as prevalent winds, which influenced individual decision- making in heading directions when foraging. Intra and interspecific competition for resources also modulated foraging distributions, avoiding conspecifics or segregating foraging areas among sympatric species in appropriate stages. In general, we have provided a complete picture of environmental processes affecting seabirds. We argue that this information would be extremely useful for designing suitable management and conservation strategies. Thus, we finally proposed an adaptive framework for delimitation of more meaningful marine reserves that maximises conservation targets for seabirds, while accounting for human activities, environmental and biological factors largely driven seabird performance and, remarkably, the dynamism inherent to marine systems.

Ce travail est une contribution à l'étude de l'écologie trophique d'importants prédateurs de la partie Nord du système du Courant de Humboldt (NSCH), le chinchard (Trachurus murphyi), le maquereau (Scomber japonicus) et le calmar géant (Dosidicus gigas). Nous avons caractérisé la variabilité des modes d'alimentation de ces espèces à différentes échelles spatiotemporelles et fourni de nouvelles connaissances sur le comportement alimentaire de ces espèces, définies comme opportunistes par des travaux antérieurs. Pour ce faire, nous avons appliqué une variété de méthodes statistiques à un vaste jeu de données comprenant 27188 estomacs non vides. Sur cette base nous avons décrit l'organisation spatiale de la faune fourrage de ces prédateurs et documenté les changements dans la composition des proies en fonction de la taille de prédateurs et des conditions environnementales. Nos résultats indiquent que l'oxygène dissous jour un rôle clef dans ces processus. Nous avons également résolu un paradoxe sur l'alimentation du calmar géant: pourquoi ils ne se nourrissent guère sur l'immense biomasse d'anchois (Engraulis ringens) présente le long de la côte du Pérou? Nous avons montré que la présence d'une zone de minimum d'oxygène (ZMO) superficielle devant le Pérou pourrait limiter la cooccurrence entre calmars géant et anchois. Pour synthétiser ces résultats, nous avons proposé un modèle conceptuel de l'écologie trophique du calmar géant tenant compte du cycle ontogénétique, de l'oxygène et de la disponibilité des proies. Par ailleurs, nous avons montré que le chinchard et le maquereau se nourrissent des espèces les plus accessibles comme par exemple la galathée Pleurocondes monodon ou les larves zoea. Ces deux prédateurs présentent un chevauchement trophique mais, contrairement à ce qui avait été décrit dans d'autres études, le chinchard n'est pas aussi vorace que le maquereau. Le régime alimentaire de ces poissons est caractérisé par une forte variabilité spatio-temporelle et le talus continental s'avère être une importante frontière biogéographique. La composition du régime alimentaire des poissons prédateurs étudiés n'est pas nécessairement un indicateur cohérent de l'évolution de la biomasse des proies. Les événements El Niño ont eu un faible effet sur le taux de remplissage des estomacs et sur le régime alimentaire du chinchard et du maquereau. Par ailleurs les changements en diversité des proies à échelle décennale contredisent le classique paradigme de corrélation positive entre diversité et température. Finalement, les patrons globaux décrits dans ce travail, illustrent le comportement alimentaire opportuniste, les stratégies de vie et le haut degré de plasticité de ces espèces. Un tel comportement permet de s'adapter aux changements de l'environnement
This work provides a contribution to a better understanding of the trophic ecology of important predators in the Northern Humboldt Current System, the jack mackerel (Trachurus murphyi), the chub mackerel (Scomber japonicus) and the jumbo squid (Dosidicus gigas) by the characterization of the highly variable feeding patterns of these species at different spatiotemporal scales. We provided new knowledge on the comparative trophic behaviour of these species, defined as opportunistic in previous investigations. For that purpose we applied a variety of statistical methods to an extensive dataset of 27,188 non-empty stomachs. We defined the spatial organization of the forage fauna of these predators and documented changes in prey composition according to predators' size and spatiotemporal features of environment. Our results highligh the key role played by the dissolved oxygen. We also deciphered an important paradox on the jumbo squid diet: why do they hardly forage on the huge anchovy (Engraulis ringens) biomass distributed of coastal Peru? We showed that the shallow oxygen minimum zone present off coastal Peru could hamper the co-occurrence of jumbo squids and anchovies. In addition, we proposed a conceptual model on jumbo squid trophic ecology including the ontogenetic cycle, oxygen and prey availability. Moreover we showed that the trophic behaviour of jack mackerel and chub mackerel is adapted to forage on more accessible species such as for example the squat lobster Pleurocondes monodon and Zoea larvae. Besides, both predators present a trophic overlap. But jack mackerel was not as voracious as chub mackerel, contradictorily to what was observed by others authors. Fish diet presented a high spatiotemporal variability, and the shelf break appeared as a strong biogeographical frontier. Diet composition of our fish predators was not necessarily a consistent indicator of changes in prey biomass. El Niño events had a weak effect on the stomach fullness and diet composition of chub mackerel and jack mackerel. Moreover, decadal changes in diet diversity challenged the classic paradigm of positive correlation between species richness and temperature. Finally, the global patterns that we described in this work, illustrated the opportunistic foraging behaviour, life strategies and the high degree of plasticity of these species. Such behaviour allows adaptation to changes in the environment

Recent (post-1950s) climate change impacts on society and ecosystems have been recognised globally. However these global impacts are not uniform at regional or local scales. Despite research progress on such scales there are still gaps in the knowledge as to 'what' is happening and 'where'? The goal of this study addresses some of these gaps by analysing climate variability and vegetation response at the furthest south westerly peninsula of the United Kingdom. This research is focused on West Cornwall (South West England) - an area dominated by a strong maritime influence. The first part of this PhD research analysed archive and contemporary instrumental data in order to detect any trends in climate variability. The weather data was retrieved from the Met Office archive for Camborne 1957-2010 and Culdrose 1985-2011 stations; Trengwainton Garden (1940-2010), and from the Royal Cornwall Polytechnic Society, for Falmouth (1880-1952) and Helston (1843-1888). The data showed positive trends in mean annual and maximum temperature with the largest trend magnitude in the 20th and 21st century. Seasonal temperature change varies locally with the highest increase in autumn spring and summer. Precipitation trends were only positive for the 19th century for Helston. Correlation between precipitation data and North Atlantic Oscillation (NAO index) was negative, however the opposite result was detected when the NAO index was correlated with temperatures. Surprisingly, return period analysis showed a decrease in the frequency and intensity of extreme precipitation events post 1975 for Camborne and Trengwainton Garden stations. The second part of this study analysed changes in vegetation distribution in West Cornwall using historical and contemporary vegetation records. Historical vegetation records were used from the Flora of Cornwall collection of herbarium records and contemporary vegetation records which were available online, containing mainly the 'New Atlas of British and Irish flora'. Data sets were geo-referenced using ArcGIS in order to analyse changes in species geographical distribution pre and post-1900. Analysis showed that historical vegetation records can be used to assess any changes in geographic distributions of vegetation. Analysis for the area of West Cornwall showed a loss of range for 18 species, for 6 species this loss was larger than 50% of the area, and there was no change in overall range area for 10 species. Ellenberg values and environmental indicator values showed that they can be used as an indicator of environmental change, showing a decrease in species with lower January temperatures. Analysis also showed an increase in moderate wetter species, where species with extreme low and high precipitation environmental indicator values showed a greater loss. Furthermore species with a higher requirement for light showed a loss as well as species with lower nitrogen values. To analyse the loss of species at the local scale, West Cornwall was divided into three areas (North Border Cells, Central West Cornwall Cells and South Border Cells). The highest loss of 11 species was detected for South Border Cells, where the loss for Central West Cornwall Cells was 6 and for North Border Cells 8 species. It was found that 17 species were experiencing loss on different local sites. For 9 of these 17 species, change at the local scale was different to the national scale change at the individual species level, group level and habitat level. Furthermore, the whole area of West Cornwall lost two species post-1900, with a different loss locally. This showed that species could be protected locally in appropriate microclimate refugia, which will be of benefit for the preservation of regional identity ecosystem services and overall genetic pool of the species.

Natural streamflow variability is important for riverine ecosystems but river regulation modifies flow patterns, disturbing fish bio-ecology. This thesis includes a characterization of basal biological differences between non-regulated permanent and temporary Mediterranean rivers and analyzes the effects of three types of regulation on fish assemblage composition, movement, diet and life-history. Fish from non-regulated permanent rivers had higher swimming performance, a higher percentage of invertebrates in their diet, mature at an older age, later in the year and have higher growth rates. By homogenizing flow pattern, regulation for water derivation and agriculture affected fluvial specialists, benefiting generalist species, promoted the consumption of plants and detritus, and decreased fish growth rates, condition and reproductive activity. Regulation for hydroeletricty induced short-term flow and habitat changes that increased fish seasonal movement and home range. These findings allow understanding bio-ecological changes imposed by flow regulation and can be used as guidelines for flow requirements implementations; Resumo: Impacto de diferentes regimes hidrológicos na bio-ecologia dos peixes dulciaquícolas em rios Mediterrânicos permanentes e temporários Esta tese inclui uma caracterização das diferenças biológicas entre rios Mediterrânicos não regularizados de regime permanente e temporário e analiza os efeitos de três tipos de regularização na composição, movimento, dieta e ciclos de vida dos agrupamentos piscícolas. Peixes de rios permanentes não regularizados apresentam uma maior capacidade natatória, um maior consumo de invertebrados, reproduzem-se mais tarde e possuem maior taxa de crescimento. Através da homogeneização do caudal, as barragens para derivação e agricultura afetam as espécies especializadas, beneficiando as generalistas, promovem o consumo de detritos e o decréscimo da taxa de crescimento, condição corporal e actividade reprodutora. A regularização para fins hidroelétricos induz uma acentuada variação do caudal e habitat, a uma escala temporal menor, contribuindo para o aumento do movimento e área utilizada pelos peixes. Estes resultados permitem compreender as alterações bio-ecologicas impostas pela regularização do caudal e podem ser usados em futuros programas de reabilitação fluvial.

Climate exerts a fundamental control on ecosystem function, species diversity and distribution. Topographic variability may influence surface climate, through processes operating at a landscape- scale. To quantify and model such influences, the topography of a 72 km(^2) area of complex terrain, (including the Moor House National Nature Reserve in northern England) was analysed at 50 m resolution. A suite of topographic variables was created, including distance relative to the Pennine ridge (dist), and elevation difference between each grid cell and the lowest grid cell within a specified neighbourhood {drain). Automatic weather stations (AWS) were deployed in a series of networks to test hypothetical relationships between landscape and climate. Daily maximum air temperature, daily mean soil temperature and daily potential evapotranspiration can be modelled spatially using a daily lapse rate calculated from the difference between daily observations made at two base stations. On days with a south easterly wind direction, daily mean temperature is estimated as a function of lapse rate and dist; the spatial behaviour of temperature is consistent with a föhn mechanism. Daily minimum temperature is modelled using lapse rate and drain on days with a lapse rate of minimum temperature shallower than -2.03 x 10 C m(^-1), incorporating the effects of katabatic air flow. Daily solar radiation surfaces are estimated by a GIS routine that models interactions between slope and solar geometry and accounts for daily variations in cloudiness and daylight duration. The daily climate surfaces were tested using data measured at a range of AWS locations during different times of year. The accuracy of the daily surfaces is not seasonally-dependent. The spatial climate data are particularly well suited to landscape-scale ecology because the methods account for prevailing topoclimatic constraints and because separate climate surfaces are generated for each day, capturing the high frequency variability characteristic of upland regions.

Variabilité spatiale multiéchelle du zooplancton dans un lagoon récifal côtier - L'identification des changements dans les patrons écologiques selon l'échelle spatiale et la compréhension des processus qui génèrent ces changements sont d'une importance considérable en océanographie. Dans ce contexte, comprendre comment une communauté biologique répond à l'hétérogénéité environnementale requiert la connaissance des processus impliqués et l'échelle spatiale à laquelle ils opèrent. Les relations spatiales entre la variabilité du zooplancton et l'hétérogénéité environnementale sont encore imprécises dans les écosystèmes tropicaux côtiers. L'objectif de ce travail de thèse a donc été de déterminer les échelles de dépendance spatiale des patrons du zooplancton associé à un lagon récifal côtier et des processus environnementaux sous-jacents. Dans ce contexte, les intérêts de cette recherche ont été de quantifier les patrons de la variabilité du zooplancton dans l'espace, de comprendre comment ces patrons changent avec l'échelle spatiale et de déterminer les processus physiques et biologiques responsables de ces patrons spatiaux. L'échantillonnage, effectué le long d'un transect de la côte vers le large dans le lagon du Grand-Cul-de-Sac Marin (Guadeloupe), a concerné deux classes de taille du zooplancton (190–600 µm et > 600 µm) pour lesquelles la biomasse et l'abondance ont été estimées. L'analyse multiéchelle a été utilisée pour caractériser les patrons du zooplancton aux différentes échelles spatiales (de l'échelle de l'habitat à celle du lagon tout entier) et pour identifier les processus responsables de ces structures spatiales. Cette étude a montré que la variabilité du zooplancton est un phénomène multiéchelle dont l'amplitude et la dépendance spatiale dépendent de la taille des organismes, de leur motilité et de la variable-réponse considérée (biomasse ou abondance). La biomasse et l'abondance du zooplancton varient en réponse à la distribution spatiale du phytoplancton, au comportement du zooplancton, à l'hétérogénéité de l'habitat, à l'hydrodynamique et aux évènements météorologiques. La nature et les effets de ces processus sont dépendants de l'échelle spatiale. Ce travail a montré comment le changement d'échelle spatiale met en évidence différents niveaux d'organisation de la communauté zooplanctonique en réponse à l'hétérogénéité environnementale.

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This study investigated the feeding ecology of zoanthids Zoanthus sociatus and Protopalythoa variabilis. Colonies of this species were sampled in the infralittoral zone of reefs in northeastern Brazil (may/2013 to february/2014). Polyps (n = 400) were examined the gastric cavity and prey found were counted, measured and identified. We calculated the richness and total abundance of prey items. The GLM test two-way ANOVA was used to compare the abundance and ricness between period and species. The biovolume of preys were calculated to characterize the most important food items in terms of their biomasses. To evaluate the selectivity, zoanthid and plankton samples were collected in the dry season and rainy. The results revealed the occurrence of seven taxa of phytoplankton and zooplankton three, and particulate organic matter. Pennales diatoms were the most abundant and most frequent prey and, together with invertebrate eggs, constituted the most important food items in terms of their biomasses. There were significant differences in abundance and richness among the species and between periods, with a significant interaction between these factors, only for abundance. The mean size of prey items within the polyps of Z. sociatus (26.35 ± 59.10 μm) and polyps of P. variabilis (26.56 ± 54.71 μm) was significantly smaller than in the plankton (54,14 ± 107,25 μm). As for the type prey, Zoanthus sociatus and Protopalythoa variabilis feed predominantly diatoms. The results, the two species are suspensívoras, feeding mainly on small phytoplankton. These results corroborate those previously found for the zoanthid P. caribaeorum in the same place, showing that this group has an important role in energy flow in reefs, transferring biomass of plankton to superiroes groups of the chain. This is fundamental to the Brazilian reefs where coverage of other suspensívoros as coral, is very low.
Este trabalho objetivou estudar a ecologia alimentar dos zoantídeos Zoanthus sociatus e Protopalythoa variabilis. Foram amostradas trimestralmente (maio/2013 a fevereiro/2014) colônias das espécies no infralitoral nos recifes da Praia de Porto de Galinhas (8º 33’ 00’’ a 8°33’33” S ; 35º 00’27’’ a 34º 59’ 00’’ W). Os pólipos (n=400) tiveram a cavidade gástrica examinada e as presas encontradas foram contabilizadas, medidas e identificadas. Foram calculadas a riqueza e abundância total dos itens de presas. O teste GLM two-way ANOVA foi usado para comparar a abundância e riqueza entre período e espécies. A partir das medições das presas, foi calculado o biovolume para caracterizar as presas com maior importância no aporte de biomassa. Para análise de seletividade foram coletadas amostras das espécies de zoantídeos e do plâncton no período seco e chuvoso. Os resultados revelaram a ocorrência de sete taxons do fitoplâncton e três do zooplâncton, além de matéria orgânica particulada. As diatomáceas pennales foram as presas mais abundantes e, juntamente, com ovos de invertebrados constituíram as presas mais importantes no aporte de biomassa. Houve diferença significativa na abundância e riqueza entre as espécies e entre os períodos, havendo interação significativa entre estes fatores, apenas para a abundância. O tamanho médio das presas presentes nos pólipos de Z. sociatus (26,35 ± 59,10 μm) e nos pólipos de P. variabilis (26,56 ± 54,71 μm) foi menor do que no plâncton (54,14 ± 107,25 μm). Quanto ao tipo de presa, Zoanthus sociatus e Protopalythoa variabilis se alimentam predominantemente de diatomáceas. Pelos resultados obtidos, as duas espécies são suspensívoras, alimentando-se principalmente de fitoplancton de pequeno porte. Esses resultados corroboram os anteriormente encontrados para o zoantídeo P. caribaeorum no mesmo local, demonstrando que este grupo tem um papel importantíssimo no fluxo de energia nos recifes, transferindo biomassa do plâncton para elos superiroes da cadeia. Isto é fundamental para os recifes brasileiros onde a cobertura de outros suspensívoros, como corais, é muito baixa.

Les invasions biologiques sont considérées comme étant une cause majeure de changement des écosystèmes. Les impacts écologiques des espèces invasives pourraient être modulés par la variabilité intraspécifique des traits biologiques et écologiques entre et au sein de leurs populations. Cette thèse a révélé, à différentes échelles spatiales, la présence de variabilités phénotypiques fortes chez deux espèces invasives, Lepomis gibbosus et Procambarus clarkii. Il est apparu que les réponses phénotypiques des individus aux conditions environnementales pourraient être complexes, révélant notamment la contre productivité des méthodes de gestion utilisées pour contrôler les populations invasives et l'importance de l'histoire de colonisation des populations dans les relations phénotype-environnement. Des expérimentations ont également démontré comment la variabilité intraspécifique pourrait moduler les effets des espèces invasives sur la structure des communautés et le fonctionnement des écosystèmes. Ces résultats soutiennent l'idée qu'intégrer la variabilité intraspécifique dans un contexte d'invasion biologique est indispensable afin de mieux évaluer les impacts et adapter les méthodes de gestion aux caractéristiques des populations invasifs
While biological invasions are widely recognized as a major cause of ecosystem changes, the ecological impacts of invasive species could be modulated by intraspecific variability in ecological traits occurring between and within populations. The present work demonstrated, at different geographical scales, the existence of a strong phenotypic variability within two freshwater invaders, Lepomis gibbosus and Procambarus clarkii. In addition, phenotypic responses to environmental conditions was demonstrated to be complex, revealing notably that the methods used to control invasive populations can be counter-productive and that the colonization history of invasive populations is an important driver of phenotype-environment relationships. Experimental approaches also demonstrated that intraspecific variability modulated the intensity of the ecological impacts of invasive species on community structure and ecosystem functioning. These findings strongly support the idea that integrating intraspecific variability in the context of biological invasions is essential to better appreciate their impacts on recipient ecosystem and ultimately improve the efficient of management methods based on the characteristics of invasive populations

Le fonctionnement écologique des écosystèmes côtiers est soumis à l’action synergique des changements climatiques et des pressions anthropiques. Au sein du Bassin d’Arcachon, l’huître Crassostrea gigas, montre depuis quelques années une modification du cycle reproductif (i.e. faible formation des gamètes, retard de ponte), qui semble lié aux modifications globales des conditions thermiques et trophiques du milieu. L’objectif de ce travail consiste à réaliser un état des lieux de la variabilité spatio-temporelle de l’état reproductif des huîtres dans le Bassin d’Arcachon, en lien avec l’origine, la quantité et la qualité de la ressource trophique. Les résultats obtenus ont permis de révéler d’importants gradients spatiaux de variabilité du développement gonadique et du signal trophique chez C. gigas, entre les parties internes sous influences des rivières (sud-est et nord-est), et la partie externe sous influences océaniques. Deux facteurs clés se sont révélés en partie explicatifs de cette variabilité, le temps d’immersion et le temps de renouvellement océanique. Un comparatif de la gamétogenèse et du pool nutritif entre les parties sud-est et nord-est du bassin a permis de démontrer une variabilité temporelle de la composition phytoplanctonique associée à une variabilité des apports en acides gras essentiels à la formation et la maturité des gamètes. La dynamique de la mise en réserves ainsi que le déclenchement des pontes chez C. gigas se sont révélés synchrones à la variabilité saisonnière de la quantité et la qualité du pool nutritif. Ces résultats représentent une première étape vers le développement d’un modèle prédictif des besoins énergétiques de l’espèce sous l’effet des changements globaux des conditions environnementales
The ecological functioning of coastal ecosystems is subjected to the synergistic action of climate change and anthropogenic pressures. In Arcachon Bay, the reproductive cycle of the oyster Crassostrea gigas has changed in recent years (e.g. weak gametogenesis, spawning delay). This pattern seems to be associated with global changes in thermal and trophic conditions. The aim of this work was to characterize the spatio-temporal variability in the reproductive investment of oysters in Arcachon Bay. This variability has been investigated in relation to the origin, quantity and quality of the trophic resources. The results revealed important spatial gradients of variability in gonadal development and trophic signal in C. gigas, between inner parts of the bay influenced by river inputs (south-east and north-east) and the external part of the bay, which is influenced by oceanic inputs. Two hydrodynamic factors explained most of the observed variability: immersion time and oceanic water renewal. A comparison of C. gigas gametogenesis and the nutritional value of available food sources between the south-eastern and north-eastern parts of the bay revealed temporal variability in the composition of phytoplankton. This variability was associated with variability in the amounts of essential fatty acids, necessary for gametogenesis. Changes in energy reserves and gamete release cycle were synchronized with the seasonal nutrient variability. These results constitute a first approach in the development of a model predicting the evolution of the energetic needs of C. gigas under the global change in environmental conditions

Temporal changes in the environmental conditions upon which life depend are ubiquitous in nature, acting at every level of organisation from cells to ecosystems. Although the actions themselves are often poorly understood, they strongly depend on the temporal and hierarchical (organisational) scales at which they are measured; ecosystems are relatively stable through time while their species composition may undergo vast changes. Likewise any hierarchical level may be relatively stable in the short-term, but undergo vast long-term changes. This thesis aims to better understand the importance of these scales for mediating the impact of environmental variability on ecological systems.
The approach used herein employs both mathematical models and empirical data which represent food webs responding to environmental variability at different hierarchical scales. Within each of these representative food webs, the influence of environmental variability on the stability of the food web is determined using an approach which accounts for the effects of temporal scale. This thesis demonstrates that the stability of simple model food webs (high hierarchical scale) is tightly linked to environmental variability and the temporal scales at which these changes occur dictate which species in the model are most affected. At lower scales of organisation, empirical data indicate that environmental variability generally has a lesser impact on stability and that only certain temporal scales are responsible for this trend. At these temporal scales some species respond differently to environmental variability, negative changes in one species (or group) are offset by positive changes in another - a process known as compensation. These results highlight the importance of both temporal and hierarchical scale in mediating the response of food webs to environmental variability. Ultimately, they will serve to better understand how models and experiments should scale-up from low to high hierarchical and temporal scales.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2008.
Includes bibliographical references (p. [221]-232).
Marine ecosystems reflect the physical structure of their environment and the biological processes they carry out. This leads to spatial heterogeneity and temporal variability, some of which is imposed externally and some of which emerges from the ecological mechanisms themselves. The main focus of this thesis is on the formation of spatial patterns in the distribution of zooplankton arising from social interactions between individuals. In the Southern Ocean, krill often assemble in swarms and schools, the dynamics of which have important ecological consequences. Mathematical and numerical models are employed to study the interplay of biological and physical processes that contribute to the observed patchiness. The evolution of social behavior is simulated in a theoretical framework that includes zooplankton population dynamics, swimming behavior, and some aspects of the variability inherent to fluid environments. First, I formulate a model of resource utilization by a stage-structured predator population with density-dependent reproduction. Second, I incorporate the predator-prey dynamics into a spatially-explicit model, in which aggregations develop spontaneously as a result of linear instability of the uniform distribution. In this idealized ecosystem, benefits related to the local abundance of mates are offset by the cost of having to share resources with other group members. Third, I derive a weakly nonlinear approximation for the steady-state distributions of predator and prey biomass that captures the spatial patterns driven by social tendencies. Fourth, I simulate the schooling behavior of zooplankton in a variable environment; when turbulent flows generate patchiness in the resource field, schools can forage more efficiently than individuals.
(cont.) Taken together, these chapters demonstrate that aggregation/ schooling can indeed be the favored behavior when (i) reproduction (or other survival measures) increases with density in part of the range and (ii) mixing of prey into patches is rapid enough to offset the depletion. In the final two chapters, I consider sources of temporal variability in marine ecosystems. External perturbations amplified by nonlinear ecological interactions induce transient ex-cursions away from equilibrium; in predator-prey dynamics the amplitude and duration of these transients are controlled by biological processes such as growth and mortality. In the Southern Ocean, large-scale winds associated with ENSO and the Southern Annular Mode cause convective mixing, which in turn drives air-sea fluxes of carbon dioxide and oxygen. Whether driven by stochastic fluctuations or by climatic phenomena, variability of the biogeochemical/physical environment has implications for ecosystem dynamics.
by Ariane Verdy.
Ph.D.

The majority of studies on plant biomass partitioning have focused on the effects of environment. Optimal Partitioning Theory (OPT) suggests that plants should allocate biomass to the organ that acquires the most limiting resource. Though, it has recently been disputed as to how much of this variation is due to variation in size and not environment. Additionally, while a few studies have examined differences between growth forms, the effects of evolutionary history have been largely ignored. Leaf morphology and physiology may also contribute to patterns of biomass partitioning.The role of plant size has been shown to be considerable to plant biomass allocation. Allometric biomass Partitioning Theory (APT) has recently been proposed to predict how plants should partition metabolic production based on the constraints of body size. Here, I assess the relative contribution of environment, growth form, leaf traits and phylogeny on variation in biomass allocation, after accounting for changes in size, using both an empirical and experimental approach. I use a global dataset of seed plants in addition to growing plants with differing evolutionary histories and growth forms hydroponically in two nutrient levels to examine patterns of organ partitioning while accounting for allometrically driven biomass allocation. Both the empirical and experimental interspecific analyses indicate that phylogeny accounts for the majority of the variation in biomass partitioning. Leaf biomass partitioning is partially related to growth form, however this appears to be due to differences in leaf morphology and physiology. While a strong phylogenetic signal exists, about half of the variation was not explained by any of the factors interspecifically, suggesting room for plasticity in partitioning. Intraspecifically, biomass allocation and partitioning was related to environmental factors in the directions predicted by OPT. However, the species-specific allocation response to environmental differences was not uniform, therefore obscuring interspecific patterns. These results have important implications for ecological studies; such that partitioning studies must first assess the role of plant size and evolutionary history in order to fully understand variability in biomass partitioning. Additionally, differences from environment can be incorporated with allometric changes to help understand how plants should allocate biomass.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Studies that aimed investigating the ecology and genetic diversity of populations of Testudines are essential to evaluate the response of aquatic communities of Testudines to human impacts and changes in the habitats of these animals. Research on this subject are few in the ecosystem of Caatinga and Atlantic Forest. Thus, in order to fill a gap in knowledge about these species, the present study aimed to investigate the conservation status of the Testudines populations located in the area of morphoclimatic Caatingas, Environmental Protection Area in the Araripe, Semi Arid region, Ceará, Northeast Brazil, regarding their population structure and genetic heterogeneity, and compile scientific actions related to the subject Testudines in northeastern Brazil. We used two traps convergence specific to clade Testudine called Covo (trap with bait), six days a month, for one year (August 2011 to July 2012). Each specimen captured was marked, sexed, had registered their biometric data and biological samples were collected for genetic analysis. For comparison of the genetic variability of populations of P. geoffroanus were used samples of Testudines collected at two points domain morphoclimatic Atlantic Forest, the Forest of Privê in Camaragibe and the Forest of Rio Paratibe in Paulista. Were captured in the area of Caatinga 63 individuals representing three species, 44 of Phrynops geoffroanus, nine of Kinosternon scorpioides and ten of Mesoclemmys tuberculata. Population size estimated by the Jolly-Seber method was 49.28±11 for K. scorpioides, 56±16.3 for M. tuberculata and 301.5 ± 67.09 for P. geoffroanus.The index of sexual dimorphism calculated the mean carapace of males and females was 1.06 (diverted for females) for P. geoffroanus and 1.04 (deflected males) for K. scopioides. We could not infer about sexual dimorphism and sex ratio for the species M. tuberculata, because only females were captured. Analysis of genetic diversity showed that the population of Caatinga showed similar genetic diversity of the populations of Atlantic forest, with genetic distance no significantly different between groups (Caatinga and Atlantic Forest), which may be the result probably of a population explosion or intense flow gene, demonstrating that despite the adverse conditions of the semi arid, the population studied in this environment presents similar adaptive capacity that populations of Atlantic Forest.
Estudos que visem investigar a ecologia e diversidade genética das populações de testudines são essenciais para avaliar a resposta das comunidades aquáticas dos testudines aos impactos antrópicos e as modificações nos habitats destes animais. Pesquisas relativas a este tema são consideravelmente poucos nos ecossistemas de Caatinga e Mata Atlântica. Desta forma, no intuito de preencher uma lacuna no conhecimento sobre estas espécies, o presente estudo objetivou investigar o status de conservação das populações de testudines localizadas no domínio morfoclimático das Caatingas, na Área de Proteção Ambiental Chapada do Araripe, região de Semi Árido, Ceará, Nordeste do Brasil, no que se refere as suas estruturas populacionais e heterogeneidade gênica, além de compilar as ações cientificas referentes ao tema Testudines no nordeste do Brasil. Foram utilizadas duas armadilhas de convergência específicas para o clado Testudine, denominada Covo (armadilha com isca), seis dias por mês, durante um ano (agosto de 2011 a julho de 2012). Cada espécime capturado foi marcado, sexado, teve seus dados biométricos registrados e foram coletadas amostras biológicas para análise genética. Para efeito de comparação da variabilidade genética das populações de P. geoffroanus foram utilizadas amostras de testudines coletadas em dois pontos do domínio morfoclimático de Mata Atlântica, Mata do Privê em Camaragibe e Mata do Rio Paratibe em Paulista. Foram capturados na área de Caatinga 63 indivíduos, representando três espécies, 44 Phrynops geoffroanus, nove Kinosternon scorpioides e dez Mesoclemmys tuberculata. O tamanho da população estimado pelo método de Jolly-seber foi de 49.28±11 para K. scorpioides ,56±16.3 para M. tuberculata e 301.5±67,09 para P. geoffroanus. O índice de dimorfismo sexual calculado com a média dos valores da carapaça dos machos e fêmeas foi de 1.06 (desviado para fêmeas) para P. geoffroanus e 1.04 (desviado para machos) para K. scopioides. Não foi possível inferir a cerca de dimorfismo sexual ou razão sexual para a espécie M. tuberculata, pois foram capturadas apenas fêmeas. A análise da diversidade genética demonstrou que a população da Caatinga apresentou diversidade genética semelhante a das populações de Mata Atlântica, não havendo distância genética significativamente diferente entre os grupos (Caatinga e Mata Atlântica), que pode ser resultado provavelmente de uma explosão populacional ou intenso fluxo gênico, demonstrando que apesar das condições adversas da caatinga, a população estudada neste ambiente apresenta semelhante capacidade adaptativa que as populações da Mata Atlântica.

Biology
Ph.D.
Species interactions are central to the study of community ecology, but these interactions can change with context. For instance, predator-prey interactions can vary with species introductions, spatial scale and temporal scale, and we are still learning how such factors can influence the strength of these interactions. Studying species interactions via multifaceted approaches and at different scales aids in the understanding of local and large scale processes, and can lead to predictions of how our ecosystems will persist in the face of continued anthropogenic alteration of the globe. The present series of studies sought to explore spatial and temporal variability in marine predator-prey interactions and invasion dynamics. The first objective was to assess biogeographic variability in predator invasions in the field. The second examined spatial variation in niche breadth via field collections, laboratory dissections, and database development, and the third involved a series of laboratory and field experiments as well as population modeling to examine temporal variability in native and non-native behavioral interactions. Specifically for the first objective, I examined the strength of marine invasive species-induced trophic cascades across latitude, hypothesizing that a non-native tertiary consumer could facilitate non-native basal prey establishment through the consumption of a native secondary consumer. I further predicted that the ecological importance of this cascade may be reduced in the subtropics relative to the temperate zone due to stronger predation pressure at lower latitudes. I found evidence of a trophic cascade in both regions, but it was only maintained under ambient predation pressure in the temperate zone. My results also suggest that strong predation pressure on the non-native intermediate predators in the subtropics may explain the weakened cascade under ambient conditions. For the second objective, I tested the hypothesis of increased specialization at lower latitudes using Brachyuran crabs as a model system and diet as my measure for niche breadth, while controlling for range size, body size and evolutionary relatedness. I compiled a dataset on 39 crab species' diets from existing studies and conducted my own diet analyses on species collected in a temperate, subtropical and tropical region, resulting in a global comparison. I found that latitudinal position was correlated with range size for temperate species, but not for tropical species, and found no correlation between the other focal variables and latitude. These results suggest that ecological mechanisms (i.e. competition strength) may be driving patterns of niche breadth in the temperate zone, while evolutionary mechanisms may be more important in predicting niche breadth patterns in tropical systems. For the third objective, I examined the influence of native and non-native prey naïveté on intermediate predator invasion success. I hypothesized that 1) naïveté is greatest in earlier stages of invasion across all trophic levels, decreasing the longer a non-native species is established in a system, 2) Native prey naïveté results in resource effects which increases invasion success, or 3) predator effects on non-native species would outweigh the importance of basal native prey naïveté, preventing an increase in non-native population growth. Through laboratory trials, I found support for naïveté being stronger at earlier stages of invasion, for both native basal prey and non-native intermediate predators. I also found weak predation on the more recently established intermediate predator in the field. However, my population model predicted that growth independent of basal prey naïveté. These results suggest that physiological traits, such as conversion efficiency and growth rates of the invasive crab may be driving its population growth more-so than foraging benefits. My studies surrounding the variability of species interactions are the first to examine the strength of invasive species-induced trophic cascades across latitude, one of very few marine empirical studies to examine diet breadth at a large spatial scale, and the first to examine multi-trophic behavioral effects on invasion success respectively. They highlight the importance of studying multi-trophic interactions, as examining more pieces of the food web is increasingly important in developing a broader understanding of interactions and adaptations within invaded communities. My research also highlights the importance of studying interactions from a macroecological perspective. Tracking both invasions and native species interactions through space and time provides insight into marine community dynamics and may elucidate possible mechanisms of species coexistence.
Temple University--Theses

Workplace Project Portfolio. Ecological study of factors associated with homicide rate variability in El Salvador, 2016. Location and dates: Homicide victims in El Salvador throughout 2016. Context: The preface provides a brief summary of the general context for this project; it is included again here to provide an adequate overview of the study. Latin America in general, and Central America in particular, are renowned for their epidemic levels of homicide rates. Inter-national as well as intra-national variability in violent crimes may provide questions and answers aimed at pinpointing key elements involved in these dynamics. It was hoped that an ecological study of municipalitylevel homicide data could provide insights to contributing factors, as well as guidance and evidence to inform possible interventions. A group of often-reported socio-economic factors were included as potential factors associated with the outcome.

Several coralligenous reefs occur in the soft bottoms of the northern Adriatic continental shelf. Mediterranean coralligenous habitats are characterised by high species diversity and are intrinsically valuable for their biological diversity and for the ecological processes they support. The conservation and management of these habitats require quantifying spatial and temporal variability of their benthic assemblages. This PhD thesis aims to give a relevant contribution to the knowledge of the structure and dynamics of the epibenthic assemblages on the coralligenous subtidal reefs occurring in the northern Adriatic Sea. The epibenthic assemblages showed a spatial variation larger compared to temporal changes, with a temporal persistence of reef-forming organisms. Assemblages spatial heterogeneity has been related to morphological features and geographical location of the reefs, together with variation in the hydrological conditions. Manipulative experiments help to understand the ecological processes structuring the benthic assemblages and maintaining their diversity. In this regards a short and long term experiment on colonization patterns of artificial substrata over a 3-year period has been performed in three reefs, corresponding to the three main types of assemblages detected in the previous study. The first colonisers, largely depending by the different larval supply, played a key role in determining the heterogeneity of the assemblages in the early stage of colonisation. Lateral invasion, from the surrounding assemblages, was the driver in structuring the mature assemblages. These complex colonisation dynamics explained the high heterogeneity of the assemblages dwelling on the northern Adriatic biogenic reefs. The buildup of these coralligenous reefs mainly depends by the bioconstruction-erosion processes that has been analysed through a field experiment. Bioconstruction, largely due to serpulid polychaetes, prevailed on erosion processes and occurred at similar rates in all sites. Similarly, the total energy contents in the benthic communities do not differ among sites, despite being provided by different species. Therefore, we can hypothesise that both bioconstruction processes and energetic storage may be limited by the availability of resources. Finally the major contribution of the zoobenthos compared to the phytobenthos to the total energetic content of assemblages suggests that the energy flow in these benthic habitats is primarily supported by planktonic food web trough the filter feeding invertebrates.

Several coralligenous reefs occur in the soft bottoms of the northern Adriatic continental shelf. Mediterranean coralligenous habitats are characterised by high species diversity and are intrinsically valuable for their biological diversity and for the ecological processes they support. The conservation and management of these habitats require quantifying spatial and temporal variability of their benthic assemblages. This PhD thesis aims to give a relevant contribution to the knowledge of the structure and dynamics of the epibenthic assemblages on the coralligenous subtidal reefs occurring in the northern Adriatic Sea. The epibenthic assemblages showed a spatial variation larger compared to temporal changes, with a temporal persistence of reef-forming organisms. Assemblages spatial heterogeneity has been related to morphological features and geographical location of the reefs, together with variation in the hydrological conditions. Manipulative experiments help to understand the ecological processes structuring the benthic assemblages and maintaining their diversity. In this regards a short and long term experiment on colonization patterns of artificial substrata over a 3-year period has been performed in three reefs, corresponding to the three main types of assemblages detected in the previous study. The first colonisers, largely depending by the different larval supply, played a key role in determining the heterogeneity of the assemblages in the early stage of colonisation. Lateral invasion, from the surrounding assemblages, was the driver in structuring the mature assemblages. These complex colonisation dynamics explained the high heterogeneity of the assemblages dwelling on the northern Adriatic biogenic reefs. The buildup of these coralligenous reefs mainly depends by the bioconstruction-erosion processes that has been analysed through a field experiment. Bioconstruction, largely due to serpulid polychaetes, prevailed on erosion processes and occurred at similar rates in all sites. Similarly, the total energy contents in the benthic communities do not differ among sites, despite being provided by different species. Therefore, we can hypothesise that both bioconstruction processes and energetic storage may be limited by the availability of resources. Finally the major contribution of the zoobenthos compared to the phytobenthos to the total energetic content of assemblages suggests that the energy flow in these benthic habitats is primarily supported by planktonic food web trough the filter feeding invertebrates.

Capítulo 1. Evaluación biológica con macroinvertebrados en ríos de la cuenca del Segura: efectos de las tendencias estacionales, métodos de procesado y resolución taxonómica sobre patrones multivariantes y métricas de diversidad.Capítulo 2. Las comunidades de macroinvertebrados de la cuenca del Río Segura: tipos de ríos, táxones indicadores y factores ambientales.Capítulo 3. Rasgos biológicos y ecológicos de los macroinvertebrados acuáticos en una cuenca semiárida. Patrones a lo largo de gradientes ambientales complejos.Capítulo 4. Riqueza, diversidad y diversidad funcional en comunidades de macroinvertebrados de la cuenca del río Segura: variaciones naturales e influencias antropogénicas.

I sistemi acquatici di transizione rivestono un ruolo fondamentale nel funzionamento degli ecosistemi marini. Nelle aree costiere italiane è presente un’unica specie di ciprinodontide, Aphanius fasciatus (Valenciennes, 1821), che svolge il suo intero ciclo vitale in questi habitat, profilandosi dunque come un tipico residente estuarino. Il presente progetto ha esplorato la possibilità di utilizzare Aphanius fasciatus come “biomonitore” delle variazioni ambientali alle quali i sistemi barenicoli della laguna di Venezia sono soggetti, investigando le risposte adattative della specie a livello di struttura genetica, demografia, tratti di life history e comportamento, articolando le analisi su differenti scale spaziali. Se da un lato non sono state registrate differenze significative nella struttura genetica di popolazione a livello lagunare, la specie ha dimostrato di possedere un’elevata plasticità fenotipica. Infatti le popolazioni si differenziano sulla base di parametri demografici, morfometria e tratti di life history legati alla riproduzione in risposta a differenti pressioni ambientali e alla struttura dell’habitat.
Transitional waters play a key role in the functioning of marine ecosystems. In the Italian coastal areas there is only one killifish, Aphanius fasciatus (Valenciennes, 1821), which spents its entire life cycle in these habitats. This project explored the possibility of using Aphanius fasciatus as "biomonitor" of environmental variability to which salt marsh systems within the Venice lagoon are subjected, investigating the adaptive responses of the species to environmental pressures at the level of genetic structure, demography, life history traits and behaviour, articulating the analysis on different spatial scales. While there were no significant differences in the genetic structure of the populations at lagoon scale, the species showed a high phenotypic plasticity. In fact, populations differ in demographic parameters, morphometry and in variations of life history traits related to reproductive investment as a response of the species to different environmental pressures and to the structure of the habitat.

Natural variability in ecosystems arises from intrinsic dynamics of both biotic and abiotic processes, which contribute to structure the variability within different levels of organization, from individuals to populations to communities. This study examined the natural variability of trophic organization as a response to different drivers of change, typical of transitional environments. Investigation was focused on fish populations of lagoon ecosystems and the variability of their trophic niche as a response to: (i) habitat heterogeneity, (ii) habitat restoration and (iii) ontogenetic development. Outcomes emerged from the three main topics highlighted the importance of the trophic adaptability of fish species that spend the entire life cycle (residents) or only one stage (migrants) within systems dominated by highly variable conditions and revealed the importance of the lagoonal habitats, including the most marginal ones and the restored ones, in supporting the trophic structure of the species investigated. In this context, management strategies of species of conservation and commercial interest should pay special attention to preserve those lagoonal habitats where populations live and reproduce, which are increasingly threatened by anthropic impact, and whose irreversible regression would result in severe loss of ecosystem functioning. La variabilità naturale degli ecosistemi è il risultato delle dinamiche intrinseche dei processi biotici ed abiotici, che contribuiscono a strutturare la variabilità dei diversi livelli di organizzazione, dagli individui, alle popolazioni, alle comunità. Questo studio ha esaminato la variabilità naturale della struttura trofica come risposta a diversi fattori di cambiamento tipici degli ambienti di transizione. L’indagine è stata focalizzata sulle popolazioni ittiche di ecosistemi lagunari e la variabilità della loro nicchia trofica in risposta a tre fattori: (i) eterogeneità di habitat, (ii) processi di rinaturalizzazione dell’habitat e (iii) sviluppo ontogenetico. I risultati emersi dai tre temi principali hanno evidenziato l'importanza dell’adattabilità trofica delle specie ittiche che trascorrono l'intero ciclo di vita (residenti) o una parte di esso (migratrici) all'interno di tali sistemi dominati da condizioni instabili e hanno indicato l'importanza degli habitat lagunari, inclusi i più marginali e quelli in fase di ripristino, nel supportare la struttura trofica delle specie esaminate. In questo contesto, le strategie di gestione delle specie di interesse, sia conservazionistico che commerciale, dovrebbero includere la conservazione degli habitat lagunari in cui le popolazioni vivono e si riproducono, i quali sono sempre più minacciati dalle impatto antropico, e la cui regressione irreversibile si tradurrebbe in una grave alterazione del funzionamento degli ecosistemi.

Nos recherches s'inscrivent dans le cadre théorique Ecological Dynamics du contrôle moteur, considérant que le comportement moteur, émerge, persiste et se réorganise en fonction des interactions de l’individu avec un ensemble de contraintes. Sur cette base, nous explorons les indices permettant de rendre compte de l’adaptation motrice du hockeyeur à diverses contraintes afin d’analyser l’expertise. À ce titre, nous avons conduit nos recherches en deux temps : i) une analyse qualitative d’entretiens semi-directifs, et ii) une analyse des paramètres superficiels (cinématique et cinétique) et profonds (coordination) du mouvement de patinage avant. À travers l’analyse de dix entretiens d’entraîneurs experts, nous avons observé que les entraîneurs faisaient appel à des connaissances « opératives » organisées en trois catégories (la posture du hockeyeur, l’action des bras, la cinématique des membres inférieurs). Cette étude nous a permis d’enrichir la connaissance des indicateurs de performances du patinage expert et de guider la conception d’un protocole expérimental représentatif du contexte écologique de pratique. La seconde partie du travail consiste en une analyse des paramètres profonds et superficiels du mouvement sous l’effet de manipulation de contraintes de tâche lors d’un sprint sur 20m. Les résultats révèlent une forte stabilité du pattern expert au niveau de l’ensemble des paramètres superficiels, ainsi qu’un mode de coordination en rattrapé et une symétrie entre les membres inférieurs, lorsque l’activité du joueur n’est pas contrainte par la conduite du palet. Cette dernière induit une flexibilité du comportement caractéristique de l’adaptabilité de l’expert
Based on the theoretical framework of Ecological Dynamics, the aim of this PhD thesis is to analyse the motor behaviour of expert ice-hockey players in relation to a set of interacting constraints. Based on this theoretical framework, our research investigates the performance indicators in order to understand how ice-hockey expert players’ behaviour emerges, persists and is reorganised when the individuals interacts with a set of constraints. We conduced our work in two stages: i) a qualitative research analysing semi-structured interviews of ice-hockey expert coaches and ii) a biomechanics analysis of forward skating. Analysing 10 ice-hockey expert coaches interviews reveals that coaches used ‘operative knowledge’ organized into three main categories (arm movement, lower limb kinematics and posture). This study allowed us to improve our understanding of performance indicators of expert forward skating. It also helped us to design a more representative biomechanics research protocol of forward skating. The second part of this thesis consists of an analysis of low-order and high-order parameters under task constraints manipulation during 20m forward sprints. Our results showed a strong stability of forward skating pattern at the low-order parameters scale as well as a stable catch-up coordination between the two feet and a stable symmetry in the lower limbs movement coordination when expert player weren’t under puck dribbling situation. When they had to run with the puck, experts’ behaviour revealed a significative variability in skating pattern organisation suggesting flexibility of experts’ behaviour in order to improve their adaptability to tasks constraints

This study aimed to improve the acoustical ecology knowledge of humpback and pygmy blue whales migrating through Geographe Bay - Western Australia. Vocalisations produced by each species were described. Vocalisation rates and detection probabilities varied between species and were dependent on temporal, behavioural and ecological parameters. Correlations between sound energy and visual observations were low for both species. This information suggests that optimal monitoring protocols for passive acoustics should be species specific.

Le bois est un tissu plurifonctionnel permettant la conduction de la sève brute, le stockage de l’eau et des sucres ainsi que le soutien mécanique de la plante. L’arbre au cours de son développement expérimente différentes contraintes liées à son environnement et à sa taille croissante. En réponse à ces contraintes, les performances fonctionnelles du bois sont ajustées par des variations de valeurs de propriétés, elles-mêmes dépendantes du produit de la xylogénèse. Cependant les extrais chimiques déposés lors du processus de duraminisation, entraine la modification des propriétés du bois. Les propriétés du duramen sont le fruit de la xylognénése et de la duraminisation ainsi que de leurs interactions. Ce travail de thèse a donné naissance au terme ‘profil ligneux’, désignant l’ensemble des variations des propriétés du bois à différentes échelles et dans une dimension ontogénique résultant des deux processus cités précédemment. La diversité de tempéraments vis-à-vis de la lumière (héliophilie à sciaphilie) des essences tropicales suggère une diversité d’expressions du profil ligneux. La description de ces différentes expressions serait gage d’une meilleure compréhension du tempérament. Comprendre et caractériser le profil ligneux et la variation de la quantité de bois de cœur dans l’arbre, représentent également un enjeu économique puisque l’industrie du bois Guyanaise a été identifiée comme une filière d’avenir. L’analyse de la diversité du profil ligneux—par une approche ascendante, de l’échelle individuelle à l’échelle interspécifique—a prouvé son efficacité dans la discrimination du degré d’affinité à la lumière. La variation de densité est particuliérment pertinente. Néanmoins, sa pertinence réside dans (1) la combinaison du gradient radial et vertical et (2) la prise en compte du duramen qui modifie parfois, l’amplitude et la direction du gradient ainsi que la forme du profil.L’effet de la duraminisation sur la variation de densité devient alors évocateur du tempérament de l’espèce au même titre que la qualité et/ou la quantité d’extraits chimique mis en jeu. La pertinence du profil ligneux dans la caractérisation du tempérament écologique est due à son aspect intégrateur de divers processus et propriétés. En regard du changement l’allocation de croissance (i.e. du tronc vers la couronne) observée chez Dicorynia guianensis et de travaux précédents sur la croissance des arbres, un lien potentiel entre la diversité du profil ligneux et la stratégie d’allocation de la croissance pourrait exister
Wood is a multifunctional tissue involved in sap conduction, storage of water and reserves as well as mechanical support. Tree during its development experiments various constraints due to its environment and its growing size. In response to these constraints, wood functional performances are adjusted by variations of property values, which are dependent on the xylogenesis product. However, wood properties may be modified by the deposition of chemical extractives during heartwood formation. Thus heartwood properties are the result of xylogenesis, heartwood formation and their interactions. This work gave rise to the term 'wood profile', designating all variations of wood properties at different scales and in an ontogenetic dimension, resulting from both processes described above. The diversity of shade tolerance (heliophilic to sciaphilic) strategies species suggests a diversity of wood profile expressions. The description of these different expressions could be a way to better understand plant strategies. Understanding and characterizing wood profile and variations in heartwood quantity in tree, is an economical issue since the Guyanese timber industry has been identified as a promising sector. The analysis of the diversity of wood profile—using a bottom-up approach, from the individual level to the interspecific level—proves to discriminate shade tolerance strategies efficiently. Wood specific gravity variation is especially relevant. However, its relevance is based on (1) combinations of both radial and vertical variations and (2) integration of heartwood that may impact range and direction of the gradient and shape of the profile as well. Effect of heartwood formation on wood specific gravity variations is suggestive of shade tolerance strategy as well as quality and/or quantity of chemical extractives. Relevant characterization of shade tolerance strategies by wood profile is the result of the integration of diverse processes and properties. To the view of growth allocation shift (from trunk to crown) observed in Dicorynia guianensis and of previous studies on tree growth, a potential link between wood profile diversity and growth allocation strategies may exist

Introduction: Mathematical models of HIV transmission have played an important role in helping to understand the drivers of the HIV epidemic, and shape the global HIV response. The underlying approaches, assumptions and structures used in HIV modelling have the potential to fundamentally influence the conclusions of any modelling analyses. For this reason, it is important that approaches to modelling HIV transmission in different contexts carefully consider how best to ‘characterise’ a populations distribution of risk and networks of sexual interaction based on data, and the implications of incorporating different levels of epidemiological complexity into their modelling. Across West Africa there are substantial variations in population HIV prevalence - ranging from 0.5-6%. To date, there has been limited exploration of the potential factors influencing this population variation. This PhD aims to inform our understanding of the determinants of population variations in HIV prevalence across West Africa, using a combination of ecological analysis of population data, and both simple and more complex epidemiological modelling. The findings are used both to explore the determinants of HIV transmission across West Africa, and to discuss the implications for future modelling and epidemic appraisal approaches. Methods: A range of modelling and epidemiological analytical approaches were used. Firstly, an existing policy model, The Modes of Transmission (MoT) model, designed to predict patterns of HIV incidence, was revised and re-parameterised using data from Nigeria, to explore the effect on overall conclusions of adding additional heterogeneity into the model, and considering more explicitly how to model HIV risk amongst lower-risk subgroups. Secondly, population data from 13 West African countries were compiled. Linear regression analyses were used to assess potential relationships between HIV prevalence in high-risk groups and population HIV prevalence and the size of high-risk population subgroups and HIV prevalence in the general population. Based on the findings from the MoT and ecological analysis, a dynamic deterministic model was developed to explore the variations in HIV prevalence across West Africa. The population model not only included sex work, client and general population sub-groups, but also included a category of adolescent females (15-24) and a category of males with multiple sexual partners, with a mixing formulation being used to vary the degree the adolescent females form partnerships with clients of female sex workers and the subgroup of males who have multiple partnerships Input parameters were sampled from ranges relevant for West Africa, using Latin Hypercube sampling. The model was fitted to equilibrium prevalence in the general population. Results: A critique and revisions to the MoT, identified high levels of infections in previously unrecognised subgroups. These included 16% of new infections occurring in young females engaging in transactional sex. Findings from the ecological analysis, showed that across West Africa HIV prevalence in FSWs and their clients is not associated with higher HIV prevalence in the general population. Instead, the size of groups of males and females with multiple partners is correlated with higher HIV prevalence levels. The deterministic model generated 11000 fits. Grouping fits, based on epidemic size (with 1% incremental increases from 0-6%), the findings revealed that population sizes of key subgroups is the predominant driver of the epidemic. For epidemics where prevalence is less than 3%, FSW population size is the most important determinant of HIV prevalence. For epidemics above 3%, it is the size of the group of adolescent females with multiple partners and their level of interaction with clients of FSWs that is the most significant variable related to higher HIV prevalence. When the limiting effects on HIV transmission of male circumcision are removed from the model, the findings are less clear, with both sex work and the role of adolescent females with multiple partners being important determinants of the epidemic. Circumcision is however shown to significantly limit the magnitude of an epidemic and epidemic categorisation should account for these variations accordingly. Conclusions: Behavioural heterogeneity has long been recognised as an important component of model development. The results from this thesis show the importance of carefully considering how to compartmentalise population HIV models. Even for simple static models, the inclusion of additional subgroups change model conclusions and suggests different intervention priorities. The use of results and findings from ecological analyses, whilst unable to provide strong evidence of causality, can provide useful insights into the relationship between population level factors or behavioural variables and HIV prevalence in the general population. These findings may then be used to inform model development. Deterministic dynamic modelling used in this thesis demonstrates that the size and sexual networks of vulnerable subgroups in the population may be of key importance in determining levels of HIV epidemics in West Africa. In-particular, adolescent females engaging in noncommercial multiple partnerships, often associated with transactional exchange are an important determinant of the HIV epidemic in West Africa. An improved understanding of this group, their size and motivations for engaging in multiple partnerships, through the use of epidemic mapping techniques and social research, will be important to future HIV intervention activities.

This thesis is a population-based epidemiological study to explore the spatial and temporal pattern of malaria, and to assess the relationship between socio-ecological factors and malaria in Yunnan, China. Geospatial and temporal approaches were applied; the high risk areas of the disease were identified; and socio-ecological drivers of malaria were assessed. These findings will provide important evidence for the control and prevention of malaria in China and other countries with a similar situation of endemic malaria.

Dengue, a mosquito borne disease, is a serious public health problem in many tropical and subtropical countries including Australia. Both climate and socio-ecological factors play significant role in dengue transmission cycle. This thesis applied spatiotemporal analytical approach to explore the joint effects of socio-ecological factors and climate variability on dengue and assess the response of dengue to climate variability across different climate zones. The findings of the thesis provide valuable information for developing early warning systems especially suitable for particular climate zone; and hence improves existing surveillance and disease prevention efforts.

[eng] This PhD thesis aims to assess the spatial and temporal patterns of phytoplankton variability and primary production in the surface waters of the Mediterranean Sea. The research is organized in three studies and it is mainly based on the use of satellite ocean color data acquired during the period 1998-2015. Complementary datasets (e.g. sea surface temperature, climatic indices, meteorological data, and atmospheric dust) are also used to address the different specific studies included in this work. A first study is aimed to analyze the contribution of the seasonal and non-seasonal components of phytoplankton variability at basin scale. Then, seasonality is analyzed from a phenological perspective i.e. by parameterizing the seasonal cycles (bloom) using a pixel-by-pixel threshold-based algorithm. We observe that seasonality dominates variability representing up to 80% of total chlorophyll (Chl) variance in oceanic areas, whereas in shelf-sea regions high frequency variations may be dominant representing up to 49% of total Chl variance. Seasonal variations are typically characterized by a phytoplankton growing period occurring in spring and spanning on average 170 days in the western basin and 150 days in the eastern basin. Also, in the western basin, a positive trend in Chl biomass and an increase in the amplitude and duration of the phytoplankton growing period is observed. On the contrary, changes in Chl concentration in the eastern (and more oligotrophic) basin are generally low, but it is observed that the Chl peak has declined and the growing period duration has also decreased. The trends in phytoplankton Chl and phenology, estimated in this study during the 1998-2014 period, do not reveal significant overall decline/increase in Chl concentration or earlier/delayed timings of the seasonal peak on average over the entire Mediterranean Sea. However, large regional variations are detected, suggesting that the response of phytoplankton to environmental and climate forcing may be complex and regionally driven. The second study addresses the regional patterns of interannual variability in satellitederived Chl. A neural network classification, based on the Self-Organizing Maps (SOM) analysis in the time domain, is used to reveal regions of simi lar temporal variability of Chl in the Mediterranean Sea. Characteristic temporal patterns extracted by the SOM analysis show different scales of variation that can be related to already identified oceanographic features and biogeochemical variability in the Mediterranean Sea. Clear differences are observed between regions located in the western basin and Adriatic Sea, where rivers, winter mixing and winds are known to drive variations in primary production at regional scale and regions located in the eastern basin, represented by a large and rather homogeneous region. The study suggests that North Atlantic Oscillation (NAO) has more influence in the Chl variations occurring in regions located in the western basin whereas El Niño Southern Oscillation index (ENSO) exhibits higher impact on the central Mediterranean and eastern basin during its positive phase. Both NAO and ENSO show non-stationary coherence with Mediterranean Chl. The analysis also reveals a sharp regime shift occurring in 2004–2007, when NAO changed from positive to negative values. This shift particularly affected the winter phytoplankton biomass and it is indicative of climate driven ecosystem-level changes in the Mediterranean Sea. The third study focusses on satellite derived primary production rates in the coastal waters of the Mediterranean Sea. We observe that 20% of the overall PP in the basin comes from shelf regions (i.e. <200m depth) and from that, most of it (~80%) is regenerated production. Almost 50% of this production occurs in the coastal waters of the eastern basin, whereas the western and Adriatic shelf contribute with 28 and 24% respectively. High regional scale variability is observed ranging from more than 350 gC m-2 yr-1 in the most productive areas, generally associated with major river discharges, to highly unproductive provinces (<50 PgC m-2 yr-1) in the south eastern Mediterranean. The long-term PP variability was dominated by interannual variations that were inversely correlated in with sea-surface temperature and more loosely with NAO and Mediterranean Oscillation Index (MOI) climatic indices. Regionally, most coastal areas presented either non-significant or weakly declining PP trends whereas positive PP trends were observed in the Adriatic region. To complete the study, a classification has been made in 18 alongshore coastal regions with mean PP magnitud es varying fivefold. Two groups of coastal waters were identified; regions showing low cross-shore variability, mainly located in narrow width shelf areas, and regions showing strong cross-shore gradients, observed in wider regions with river discharges. Approximately 50% of the global primary production takes place in the ocean and, consequently, marine phytoplankton play a fundamental role in global carbon fluxes. Studying the spatial and temporal variability of phytoplankton, as well as estimating factors that determine this variability, is essential to understand the dynamics, productivity and biogeochemical cycles of the ocean, and to anticipate the effects of climate change on the marine environment. It is expected that this PhD thesis can contribute to a better understanding of these changes in the Mediterranean Sea.
[spa] La presente tesis doctoral tiene como objetivo evaluar los patrones espaciales y temporales de la variabilidad del fitoplancton marino y la producción primaria en las aguas superficiales del mar Mediterráneo. La investigación se organiza en tres estudios y se basa principalmente en el uso de datos de satélite del color del océano adquiridos durante el período 1998-2015. Asimismo, datos complementarios (por ejemplo, temperatura superficial del mar, índices climáticos, datos meteorológicos o concentración de polvo atmosférico) son utilizados para abordar cuestiones específicas. El primer estudio tiene como objetivo analizar la contribución de las componentes estacionales y no estacionales de la variabilidad del fitoplancton en la cuenca del mar Mediterráneo. La componente estacional se aborda mediante la caracterización de la fenología del fitoplancton; es decir, mediante la parametrización de los ciclos estacionales su periodo de floración (bloom). Para ello, se ha utilizado un algoritmo basado en detección de umbrales de crecimiento de la biomasa de fitoplancton que ha sido ejecutado píxel a píxel. Los resultados demuestran que la variabilidad debida a la componente estacional puede suponer hasta el 80% de la varianza total de clorofila (Chl) en áreas oceánicas, mientras que en las regiones de plataforma continental la variabilidad de alta frecuencia puede dominar y representar hasta un 49% de dicha variabilidad total de Chl. Las variaciones estacionales típicamente se caracterizan por un período de crecimiento del fitoplancton que se produce en primavera y abarca en promedio 170 días en la cuenca oeste u occidental y 150 días en la cuenca este u oriental. Además, en la cuenca occidental se observa una tendencia positiva en la biomasa de Chl y un aumento en la amplitud y duración del período de floración del fitoplancton. Por otro lado, en la cuenca oriental (y más oligotrófica) las tendencias en la concentración de Chl son generalmente despreciables, pero el valor máximo de Chl alcanzado durante el bloom y la duración del periodo de crecimiento si muestran una disminución. A nivel de toda la cuenca del mar Mediterráneo, las tendencias en el fitoplancton y en la fenología, estimadas en este estudio durante el período 1998-2014, no revelan en promedio ni una disminución/aumento general significativo en la concentración de Chl ni un avance/retraso del valor máximo de biomasa estacional. Sin embargo, sí se detectan grandes variaciones regionales, sugiriendo que la respuesta del fitoplancton a las variables ambientales y climáticas pueda ser compleja y local. El segundo estudio aborda los patrones regionales de variabilidad interanual en series temporales de Chl derivadas de datos de satélites. Se utiliza una clasificación de redes neuronales de aprendizaje no supervisado basada en el análisis de Mapas de Autoorganización (SOM, de las siglas en inglés Self-Organizing Maps) ejecutados en el dominio temporal, con el objetivo de discernir regiones donde la variabilidad temporal de la Chl sea similar en el mar Mediterráneo. Los patrones temporales característicos extraídos a través del análisis SOM muestran diferentes escalas de variación que pueden relacionarse con las características oceanográficas y con la variabilidad biogeoquímica presente en el mar Mediterráneo. Se observan claras diferencias entre las regiones ubicadas en la cuenca occidental y el mar Adriático, donde se sabe que los ríos, la mezcla de invierno y los vientos impulsan variaciones en la producción primaria a escala regional; y también en las regiones ubicadas en la cuenca oriental, representadas por una gran región bastante homogénea. El estudio sugiere que el índice climático North Atlantic Oscillation (NAO) tiene una influencia mayor en las variaciones de Chl ubicadas en la cuenca occidental, mientras que el índice El Niño Southern Oscillation (ENSO) muestra un mayor impacto en la cuenca central del Mediterráneo, principalmente apreciable durante su fase positiva. Tanto NAO como ENSO muestran coherencia no estacionaria con la variabilidad de la Chl en el Mediterráneo. El análisis también revela un cambio brusco producido durante los años 2004-2007, cuando el índice NAO cambió de valores positivos a negativos. Este cambio afectó particularmente a la biomasa de fitoplancton en invierno y es un claro indicador del impacto climático sobre el ecosistema del mar Mediterráneo. El tercer estudio se centra en las tasas de producción primaria en las aguas costeras del mar Mediterráneo estimadas mediante datos de satélites. El estudio revela que aproximadamente el 20% del total de la producción primaria de la cuenca Mediterránea proviene de áreas situadas en la plataforma continental (<200 m de profundidad) y que, además, la mayor parte (~80%) constituye producción regenerada. Casi el 50% de esta producción ocurre en las aguas costeras de la cuenca oriental, mientras que las plataformas occidental y Adriática contribuyen con el 28 y el 24% respectivamente. Se observa una gran variabilidad a escala regional que varía desde zonas muy productivas que superan 350 gC m-2 al año, típicamente situadas en las áreas más productivas asociadas con descargas de ríos importantes, a zonas altamente improductivas (<50 PgC m-2 al año) situadas principalmente en el sureste Mediterráneo. La variabilidad de la producción primaria a largo plazo está dominada por variaciones interanuales que se correlacionan inversamente con datos de temperatura superficial del mar y, del mismo modo, aunque en menor grado, con los índices climáticos NAO y Mediterranean Oscillation Index (MOI). A escala regional, la mayoría de las áreas costeras presentan tendencias de producción primarias no significativas o con un débil declive. No obstante, se observan tendencias de producción primaria altamente positivas en el mar Adriático. Para finalizar el estudio, se ha hecho una clasificación en 18 regiones costeras con valores medios de producción primaria que pueden quintuplicarse entre regiones. Además, el análisis permite la identificación de dos grupos de aguas costeras: por un lado, regiones que muestran una baja variabilidad a lo largo de la costa, ubicadas principalmente en áreas donde la plataforma continental es estrecha; y por otro lado regiones que muestran fuertes gradientes a lo largo de la costa, situadas en regiones donde la plataforma continental es típicamente más ancha y/o existen descargas de ríos. Aproximadamente el 50% de la producción primaria mundial tiene lugar en el océano y, en consecuencia, el fitoplancton marino desempeña un papel fundamental en los flujos globales de carbono. Estudiar la variabilidad espacial y temporal del fitoplancton, así como estimar los factores que determinan esta variabilidad, es esencial para comprender la dinámica, la productividad y los ciclos biogeoquímicos del océano, y para anticipar los efectos del cambio climático en el ecosistema marino. Se espera que esta tesis doctoral pueda contribuir a una mejor comprensión de estos cambios en el mar Mediterráneo.
[cat] La present tesi doctoral té com a objectiu avaluar els patrons espacials i temporals de la variabilitat del fitoplàncton marí i la producció primària a les aigües superficials de la mar Mediterrània. La investigació s'organitza en tres estudis i es basa principalment en l'ús de dades de satèl·lit del color de l'oceà adquirides durant el període 1998-2015. Així mateix, dades complementàries (per exemple, temperatura superficial de la mar, índexs climàtics, dades meteorològiques o concentració de pols atmosfèrica) són utilitzats per abordar qüestions específiques. El primer estudi té com a objectiu analitzar la contribució dels components estacionals i no estacionals de la variabilitat del fitoplàncton en el conjunt de la mar Mediterrània. El component estacional s'aborda mitjançant la caracterització de la fenologia del fitoplàncton; és a dir, a costa de la parametrització dels cicles estacionals del seu període de floració (bloom). Per aconseguir-ho, s'ha utilitzat un algoritme fonamentat en la detecció de frontera que ha estat executat píxel a píxel. Els resultats assenyalen que la variabilitat deguda al component estacional pot suposar fins al 80% de la variància total de clorofil·la (Chl) en zones oceàniques, mentre que a les regions de plataforma continental la variabilitat d'alta freqüència pot dominar i representar fins a un 49% d'aquesta variabilitat total de Chl. Les variacions estacionals típicament es caracteritzen per un període de creixement del fitoplàncton que es produeix a la primavera i presenta de mitjana 170 dies a la conca oest o occidental i 150 dies a la conca est o oriental. A més, en la conca occidental s'observa una tendència positiva en la biomassa de Chl i un augment en l'amplitud i duració del període de floració del fitoplàncton. D’altra banda, en la conca oriental (i més oligotròfica) els canvis en la concentració de Chl són generalment menyspreables, però si que el valor màxim de Chl assolit durant el bloom s'ha reduït, alhora que la duració del període de creixement també ha disminuït. En referència a tota la conca de la mar Mediterrània, les tendències en el fitoplàncton i en la fenologia, estimades en aquest estudi durant el període 1998-2014, no mostren de mitjana cap disminució/augment general significatiu en la concentració de Chl ni tampoc un avanç/retard del màxim estacional. No obstant això, si que es detecten grans variacions regionals, suggerint que la resposta del fitoplàncton als forçaments ambientals i climàtics pugui ser complexa i local. El segon estudi aborda els patrons regionals de variabilitat interanual en sèries temporals de Chl derivades de dades de satèl·lits. S'utilitza una classificació de xarxes neuronals d'aprenentatge no supervisat basada en l'anàlisi de Mapes d' Autoorganització (SOM, de les sigles en anglès Self-Organizing Maps) executats en el domini temporal, amb l'objectiu de discernir regions on la variabilitat temporal de la Chl sigui similar a la mar Mediterrània. Els patrons temporals característics extrets mitjançant l'anàlisi SOM mostren diferents escales de variació que poden relacionar-se amb les característiques oceanogràfiques i amb la variabilitat biogeoquímica present en la mar Mediterrània. S'observen clares diferències entre les regions situades a la conca occidental i el mar Adriàtic, on se sap que els rius, la barreja d’aigües que passa al mar a l'hivern, i els vents impulsen variacions en la producció primària a escala regional; i també en les regions situades a la conca oriental, representades per una gran regió bastant homogènia. L'estudi suggereix que l'índex climàtic North Atlantic Oscillation Index (NAO) té una influència més gran en les variacions de Chl ubicades a la conca occidental, mentre que l'índex El Niño Southern Oscillation (ENSO) mostra un major impacte en la conca central de la Mediterrània principalment apreciable durant la seva fase positiva. Tant NAO com ENSO mostren coherència no estacionària amb la variabilitat de la Chl a la Mar Mediterrània. L'anàlisi també revela un canvi sobtat produït durant els anys 2004- 2007, quan l'índex NAO va canviar de valors positius a negatius. Aquest canvi va afectar particularment la biomassa de fitoplàncton a l'hivern i és indicatiu clar de canvis en el nivell de l'ecosistema impulsats pel clima en la mar Mediterrània. El tercer estudi se centra en les taxes de producció primària a les aigües costaneres de la mar Mediterrània estimades mitjançant dades de satèl·lits. L'estudi revela que aproximadament el 20% del total de la producció primària de la conca mediterrània prové d'àrees situades a la plataforma continental (<200 m de profunditat) i que, a més, la major part (~80%) constitueix producció regenerada. Gairebé el 50% d'aquesta producció es produeix en les aigües costaneres de la conca oriental, mentre que les plataformes occidental i Adriàtica contribueixen amb el 28 i el 24% respectivament. S'observa una gran variabilitat a escala regional que varia des de zones molt productives que superen 350 gC m-2 a l'any, típicament situades a les àrees més productives generalment associades amb descàrregues de rius importants, fins a províncies altament improductives (<50 PgC m-2 al any) situades principalment al sud-est mediterrani. La variabilitat de la producció primària a llarg termini és dominada per variacions interanuals que es correlacionen inversament amb dades de temperatura superficial del mar i, de la mateixa manera encara que en menor mesura, amb els índexs climàtics NAO i Mediterranean Oscillation Index (MOI). En l’àmbit regional, la majoria de les àrees costaneres presenten tendències de producció primàries no significatives o amb un lleuger declivi, encara que, si bé s'observen tendències de producció primària altament positives al mar Adriàtic. S'han classificat les aigües costaneres en 18 regions amb valors mitjans de producció primària que poden variar fins a cinc vegades d’unes regions a altres. L'anàlisi permet la identificació de dos grups d'aigües costaneres: d'una banda, regions que mostren una baixa variabilitat al llarg de la costa, situades principalment en àrees on la plataforma continental és estreta; i d'altra banda regions que mostren forts gradients al llarg de la costa, situades en regions on la plataforma continental és típicament més ampla i/o hi ha descàrregues de rius. Aproximadament el 50% de la producció primària mundial té lloc a l'oceà i, en conseqüència, el fitoplàncton marí té un paper fonamental en els fluxos globals de carboni. Estudiar la variabilitat espacial i temporal del fitoplàncton, així com estimar els factors que determinen aquesta variabilitat, és essencial per comprendre la dinàmica, la productivitat i els cicles biogeoquímics de l'oceà, i per anticipar els efectes del canvi climàtic en l'ecosistema marí. S'espera que aquesta tesi doctoral pugui contribuir a una millor comprensió d'aquests canvis a la Mediterrània.

Intermittent streams that cease to flow for some period of most years are prevalent across global river networks. Their spatial extent is projected to increase in regions experiencing drying trends related to climate change and water extraction for human uses. Intermittent streams sustain biodiversity by hosting a unique combination of aquatic, amphibious, and terrestrial assemblages as a result of their wet and dry phases. Compared to perennial streams, the ecological values of intermittent streams are not well-appreciated or understood, and thus intermittent streams are less commonly incorporated into policy, management, and regulatory decisions. As research on intermittent streams is increasing, there have been strident calls for better recognition and protection of intermittent streams. This thesis aims to develop new methods to address some key issues related to spatio-temporal dynamics and hydro-ecology of intermittent streams, with a focus on eastern Australia. River channel drying caused by intermittent stream flow is a widely-recognised factor shaping stream ecosystems. There is a strong need to quantify spatio-temporal variations in the hydrology of intermittent streams over broad spatial scales to inform ecological understanding and management. This is challenging because observational stream gauges are sparsely distributed and provide only point estimates of discharge. In this study, I developed models to simulate monthly discharge across river catchments. Due to the common issue of over-estimating low flows in discharge simulations, I also identified appropriate zero flow thresholds to mitigate this uncertainty. I quantified spatial and temporal patterns of flow intermittency for every stream segment within river networks of five major catchments in south-eastern Queensland (SEQ), eastern Australia. Results showed that the temporal dynamics of flow intermittency varied dramatically inter-annually over the period of 1900-2016, with the proportion of intermittent streams ranging in length from 3 % to nearly 100% of river networks, but there was no evidence of an increasing trend towards flow intermittency over this period. This approach to generating spatially explicit and catchment-wide estimates of streamflow intermittency can facilitate improved ecological understanding and management of intermittent streams. Compared with monthly discharge simulations, daily discharge simulations can provide more detailed representation of the dynamic aspects of hydrological processes and potentially enables more ecologically relevant characterisation of hydrology. However, models of daily stream flow are more complex and often need to take river routing processes into account. I developed models to simulate daily stream flows for contiguous sub-catchments across entire river networks in two hydro-climatically distinctive regions (SEQ vs. the Tamar River II catchment). I evaluated the models in terms of their ability to represent different ecologically important components of flow regime and quantified environmental correlates of differences in model accuracy within and between regions. The models showed generally good performance in both regions. However, average- and high flows were better predicted than low flows in SEQ because it is difficult to represent climate and hydrogeological processes influencing the low-flow part of the hydrograph. Spatial variation in flow characteristics revealed the highly dynamic nature of flow permanence in space and time, with intermittent flows affecting between 29% and 80% of the river network over the period of 1911-2017. I discuss the pros and cons of the applications of modelled monthly and daily flows, and conclude that the appropriate choice of modelling time step depends on the primary objectives of the research. The monthly time-step is suitable for quantifying ecologically relevant spatial and temporal variations in streamflow intermittency, but may be insufficient for studies aimed at quantifying ecological responses to short term flow events. The hydrological variability of intermittent streams poses challenges for resident aquatic biota which require access to permanent surface water-bodies to persist during dry spells and to recolonise suitable habitats when flows resume. However, research to quantify the dynamics and environmental determinants of variation in surface water extent is usually conducted over limited spatial and/or temporal extents. One of the biggest barriers to this kind of research is the difficulty in obtaining observed data of surface water extent across river networks. In this study, I demonstrated a newly-developed field method for rapid surface water assessment, and then developed predictive models relating observed water extent to environmental attributes at 241 surveyed stream segments in SEQ. I used the models to predict daily variations in surface water dynamics throughout entire river networks over the past century, based on available long-term environmental attributes. Descriptors of surface water extent could be accurately modelled, with good internal and external validation performance. Long-term variations in surface water extent were highly dynamic through space and time, although the overall length of river networks with surface water remained relatively stable from year to year. This study provides valuable insights into the potential priority conservation areas for aquatic biota across the study region. Systematic conservation prioritisation methods are increasingly being applied to freshwater ecosystems to identify candidate areas for ecosystem management and biodiversity protection. However, applications with emphasis on intermittent streams are scarce. The hydrological variability of intermittent streams means that the spatial distribution of dry season aquatic refuges within river networks and the temporal dynamics of hydrological connectivity between them are critical for the persistence of aquatic biodiversity. I developed a new approach to incorporating both surface water persistence and hydrological connectivity into systematic conservation prioritisation in intermittent streams. I also included multiple freshwater fish species distributions as explicit targets for habitat prioritisation, and incorporated estimates of their relative mobility to maximise potentially re-colonisable stream length from refuges. Compared with the situation without mobility, the inclusion of species mobility could significantly reduce the number of aquatic refuges required to meet the set conservation targets. High priority aquatic refuges were widely distributed across the study river networks, encompassing streams in various orders from main stems to headwaters. The research can help enhance both the resistance and resilience of freshwater biodiversity in intermittent stream ecosystems. The thesis concludes with practical learnings from these modelling studies for intermittent stream research and management, namely, 1) that discharge simulations (monthly or daily) throughout river networks confirmed the prevalence of intermittent streams and revealed the highly dynamic nature of flow intermittency over space and time; 2) that spatial and temporal dynamics of surface water availability within stream reaches can be modelled through the combination of observed surface water extent with long-term environmental attributes; and 3) that systematic prioritisation of aquatic refuges by incorporating both surface water persistence and hydrological connectivity enables to efficiently meet conservation targets for species representation and cost-effective conservation management. The thesis also concludes with future challenges and directions for intermittent stream research.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

Amazonian evergreen forests are of broad interest, attributable to their ecological, economic, aesthetic, and cultural importance. However, their fate under climate change remains uncertain, largely due to unclear mechanisms in regulating tropical photosynthetic metabolism. Understanding mechanistic controls on these dynamics across time scales (e.g. hours to years) is essential and a prerequisite for realistically predicting tropical forest responses to inter-annual and longer-term climate variation and change. Tropical forest photosynthesis can be conceptualized as being driven by two interacting causes: variation due to changes in environmental drivers (e.g. solar radiation, diffuse light fraction, and vapor pressure deficit) interacting with model parameters that govern photosynthetic behavior, and variation in photosynthetic capacity (PC) due to changes in the parameters themselves. In this thesis, I aim to reveal photosynthetic controls by addressing three fundamental but complementary questions: (1) What are the mechanisms by which the subtle tropical phenology exert controls on tropical photosynthetic seasonality? (2) How do the extrinsic and intrinsic controls regulate the photosynthesis processes at hourly to interannual time scales in an Amazonian evergreen forest? (3) Are there sufficiently consistent relations among leaf traits, ages, and spectra that allow a single model predict the leaf aging process of Amazonian evergreen trees? To address question 1, I firstly show that seasonal change in ecosystem-scale photosynthetic capacity (PC), rather than environmental drivers, is the primary driver of seasonality of gross primary productivity (GPP) at four Amazonian evergreen forests spanning gradients in rainfall seasonality, forest composition, and flux seasonality. Using novel near-surface camera-detected leaf phenology to drive a simple leaf-cohort canopy model at two of these sites, I further show that leaf ontogeny and demography explain the changes in ecosystem photosynthetic capacity. The coordination of new leaf growth and old leaf divestment (litterfall) during the dry season shifts canopy composition towards younger leaves with higher photosynthetic capacity, driving large seasonal increases (~27%) in ecosystem photosynthetic capacity. To address question 2, I used the 7-year eddy covariance (EC) measurements in an Amazonian tropical evergreen forest. I used a statistical model to partition the variability of 7-year EC-derived GPP into two main causes: variation due to changes in extrinsic environmental drivers and variation in intrinsic PC. The fitted model well predicts variability in EC-derived GPP at hourly (R²=0.71) to interannaul (R²=0.81) timescales. Attributing model predictions to causal factors at different timescales, I find that ~92% of the variability in modeled hourly GPP could be attributed to environmental driver variability, and ~5% to variability in PC. When aggregating the modeled GPP into the annual time-step, the attribution is reversed (only ~4% to environment and ~91% to PC). These results challenge conventional approaches for modeling evergreen forests, which neglect intrinsic controls on PC and assume that the primary photosynthetic control at both long and short timescales is due to changes in the hourly-to-diurnal environment on the physiological phenotype. This work thus highlights the importance of accounting for differential regulation of different components of GPP at different timescales, and of identifying the underlying feedbacks and adaptive mechanisms which regulate them. To address question 3, I explored the potential for a general spectrally based leaf age model across tropical sites and within the vertical canopy profiles using a phenological dataset of 1831 leaves collected at two lowland Amazonian forests in Peru (12 species) and Brazil (11 species). This work shows that a simple model (parameterized using only Peruvian canopy leaves) successfully predicts ages of canopy leaves from both Peru (R²=0.83) and Brazil (R²=0.77), but ages for Brazilian understory leaves with significantly different growth environment and leaf trait values have lower prediction accuracy (R²=0.48). Prediction accuracy for all Brazilian samples is improved when information on growth environment and leaf traits were added into the model (5% R² increase; R²=0.69), or when leaves from the full range of trait values are used to parameterize the model (15% R² increase; R²=0.79). This work shows that fundamental ecophysiological rules constrain leaf traits and spectra to develop consistently across species and growth environment, providing a basis for a general model associating leaf age with spectra in tropical forests. In sum, in this thesis, I (1) conceptualize photosynthesis as being driven by two interacting dynamics, extrinsic and intrinsic, (2) propose and validate a model for biological mechanisms that mediate seasonal dynamics of tropical forest photosynthesis, (3) assess and quantify the factors controlling tropical forest photosynthesis on timescales from hourly to interannual, and (4) develop a general model for monitoring leaf aging processes of tropical trees across sites and growth environments. The revealed mechanisms (and proposed models) in this thesis greatly improve our mechanistic understanding of the photosynthetic and phenological processes in tropical evergreen forests. Strategic incorporation of these mechanisms will improve ecological, evolutionary and earth system theories describing tropical forests structure and function, allowing more accurate representation of forest dynamics and feedbacks to climate in earth system models.

How does variability in nectar secretion rates affect the interaction between hummingbirds and the plants that: they pollinate? Other researchers have suggested that variability may influence pollinators to leave a plant earlier, thus increasing the potential for cross-pollination. My dissertation asks the following questions: Does variability in nectar secretion rates influence hummingbird visitation at a flower patch? Does it do so in a manner that is likely to increase; cross-pollination? And, does variability in these rates benefit the hummingbird by improving their foraging efficiency? By asking if variability benefits both plants and hummingbirds, I implicitly ask the question: Can variability in nectar secretion rates be a mechanism that helps keep this potentially antagonistic interaction positive? I developed an artificial flower that simulates nectar secretion. Using patches of these artificial flowers, I varied renewal rates of flowers found within a patch. The appendices describe the results of my studies. The aviary experiment (Appendix A) investigates how Broad-billed hummingbirds (Cynanthus latirostris) forage given variability in nectar renewal-rates. The field experiment (Appendix B) investigates how hummingbird visitation to patches with different renewal-rates might affect cross-pollination. Appendix C describes the hummingbird community at the study site. Appendix D identifies the plants visited by these hummingbirds. In the aviary experiment, Broad-billed hummingbirds changed their foraging when exposed to high variability and limited nectar. They visited a higher percentage of rewarding flowers, foraged more systematically, and significantly decreased their foraging time. These changes made their foraging more efficient. In the field experiment, increased renewal-rate variability was associated with hummingbirds visiting fewer artificial flowers per foraging bout. These results suggest cross-pollination may be increased. However, levels of renewal-rate variability did not affect the visitation rates to the flower patch or the distribution of nectar within the patch. Hummingbirds spent significantly more time probing the last flower in a foraging bout than other flowers, and preferentially ended foraging bouts on a rapidly renewing flower. I suggest that the energetic cost of hovering flight likely influenced this behavior. My results support the hypothesis that variability in nectar secretion rates may benefit both partners in this pollination mutualism.

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FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais
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Reservoirs are significant sources of carbon emission to the atmosphere. However the magnitude of this emission has huge uncertainties, partly related to the methods of sampling and partly related to the unconsidered spatial-temporal variability. Here we examined the spatial variability and its drivers of partial pressure, gas exchange coefficient and diffusive flux of CO2 and CH4 in three tropical reservoirs. We observed high spatial variability in CO2 and CH4 concentration and flux within the reservoirs. Our results suggest that all reservoirs were supersaturated in both gases, even considering that some areas were CO2 sinks. A large spatial variability in k600 for CO2 and CH4, and consistently observed k600CH4 values higher than k600CO2 were also observed in all reservoirs. We could explain the high spatial variability of CO2 and CH4 by a combination of parameters such as dissolved oxygen, pH, chlorophyll, wind speed and bathymetry. Finally, we suggest a minimum sampling effort required to representatively cover a study site. Our results illustrate the first specially-resolved analysis of CH4 emissions in reservoirs, and we suggest that in large systems (area ≥ 1,000 km²) and small systems (area ≤ 100 km²), 600 and 200 measurements sites, respectively, are need for a representative dry period carbon flux estimates.

Large scale shifts playing out on global climate levels are manifesting locally in the South Africa’s terrestrial and marine ecosystems, where it is difficult to predict how different habitats may respond to these changes in natural systems, particularly at local levels. For example, the highly complex nature of climate variability in the southern Cape and on the Agulhas Bank, coupled with the lack of long-term environmental monitoring data, has resulted in knowledge gaps on how climate impacts these local social-ecological systems. This thesis focuses on bringing together knowledge systems from farmers, handline fishers and local scientific weather sources to examine climate variability in terrestrial and marine social-ecological systems of the southern Cape, in order to bring local perspectives into conversation with scientific data outputs. Through examining different knowledge systems in parallel and overlaying different perspectives and observations, this thesis contributes towards a better understanding of complex systems change, linked through the common thread of climate variability under a resilience lens, at the local scale of the southern Cape and Agulhas Bank. This thesis also contextualises responses to change under the theme of climate variability from farmers’ and fishers’ perspectives, and shows how different theoretical discourses can work in a complementary fashion to address complexity. The terrestrial component of this thesis examined local agricultural perspectives by surveying southern Cape farmers, and built in terrestrial scientific data through looking at local climate in relation to farming perspectives. Observations on terrestrial rainfall and temperatures were collected through interviews with 50 farmers, along with shared rainfall records from 13 farming families and ten official weather stations in the area. Fisher perspectives in relation to climate variability were then integrated with marine scientific data to examine the marine component of the Agulhas Bank. Fisher observations of climate variability were examined by drawing on existing research conducted through the South Coast Interdisciplinary Research Project. Marine wind data were obtained through model outputs from NCEP-DOE Reanalysis and a recent scatterometer-based product. Overlaying these different bodies of knowledge reduced the uncertainties associated with any single set of observations and confirmed two environmental regime shifts in the region, in the mid-1990s and end-2000s. Local climate knowledge of farmers and fishers also overlapped and corroborated these environmental regime shifts. Changes in prevailing wind direction, rather than wind speed, were more prominent over time. While no clear trends of change over time were found in rainfall and temperature time series, decadal variability was present and after the mid-2000s, the onset of seasonal autumn rainfall was found to have shifted to a month later. Knowledge disconnects were broadly related to scale mismatches between fisher observations and marine data tendencies; complexities around freshwater availability; and shifting baselines of natural resources concerning present versus past variability observed by farmers and fishers. Responses to climate variability were complex and other stressors associated with economic and political challenges were usually seen as a greater threat to local livelihoods. However, climate stressors can push social-ecological systems into vulnerable states if not well integrated into adaptation strategies, which can have serious implications for future food and job security in the southern Cape. Local-based case studies such as this one increase understanding of local social-ecological systems under global change in an effort to contribute to future adaptation strategies in the southern Cape region.

Thesis (Ph. D.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Les formes de croissance végétales ont fait l'objet de nombreuses études mais elles constituent encore aujourd'hui un ensemble mal défini et sans cesse remis en question en raison de l'incohérence et de l'hétérogénéité des méthodes employées pour les analyser. Cette imprécision a des répercussions négatives lorsque les formes de croissance sont utilisées dans l'étude des communautés végétales et de leur dynamique. Nous avons tenté de remédier partiellement à cette situation en appliquant à certaines d'entre elles la méthode d'analyse architecturale initiée par Hallé et Oldeman dont l'efficacité s'est avérée remarquable pour la compréhension des formes arborescentes.L'étude était destinée 1) à interpréter ces formes de croissance et leur variabilité à l'aide des concepts architecturaux, 2) à suivre les changements des traits architecturaux au sein d'une communauté végétale se développant sur des talus, lors d'une chronoséquence et en fonction de différents gradients environnementaux. Nos observations montrent que 1) les concepts et les traits architecturaux sont applicables aux formes de croissance herbacées, suffrutescentes, et buissonnantes, 2) l'expression de la réitération est la source principale de variation structurale des formes de croissance aussi bien à l'échelle spécifique qu'infra-spécifique, 3) la valeur des traits architecturaux change au cours de la succession au sein de la communauté : les plantes vivant sur des talus jeunes ont une unité architecturale simple et réitèrent à la base alors que celles croissant sur des talus plus anciens ont des unités architecturales complexes et réitèrent de manière acrotone.Ces résultats nous conduisent à discuter de la valeur holistique de la méthode d'analyse architecturale pour la caractérisation des formes de croissance, des processus biologiques permettant de passer d'une forme de croissance à une autre et de l'intérêt pratique de l'utilisation des traits architecturaux dans l'étude des communautés végétales
The growth forms of plant have been studied many times but they still represent nowadays a fuzzy set, often modified because of the inconsistency and the heterogeneity of the methods used in their analysis. This lack of precision often leads to an inconsistency of the use of the growth forms as a trait in the studies of plants communities and their dynamics. We tried to remedy this situation by applying to some of them the architectural analysis initiated by Hallé and Oldeman, which has been relevant for the understanding of the tree growth form.This study aimed to 1) interpret these growth forms and their variability by means of architectural concepts, 2) study architectural traits variation within roadsides plants communities during succession and in a mowing context. Our resultats show that 1) the architectural concepts and traits are applicable to herbaceous, treelet and bush grosth forms, 2) the expression of the reiteration is the main source of structural variation of growth forms at specific and intraspecific levels and 3) that traits values are changing during succession within the communities : Plants living at early successionnal stages got a simple architectural unit and reiterate at the base of the individual while plants living at late successional stages got complex architectural unit and acrotonic reiteration.These resultats lead us to discuss the holistic value of the architectural analysis for growth forms charaterisation, of biological processes allowing for growth form variation and the interest of the use of architectural traits in plant communities studies

Hawaiian lowland wet forest (HLWF) plant species are light-limited, yet no information exists on how the understory light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked. I measured the red-to-far-red ratio (R:FR) of light to assess light quality and quantified diurnal variability in three forest types: native-dominated, partially-invaded, and fully invaded by strawberry guava (Psidium cattleianum). I asked: (1) how does understory light quality vary relative to invasion? (2) Are there differences in light quality moving vertically among forest types? (3) Are patterns of seedling regeneration and understory light related? Native-dominated forests had the greatest light quality (highest R:FR), and Psidium cattleianum-dominated forests had the lowest. While I predicted that native seedlings would prefer high-quality light sites, all seedlings preferred medium quality environments. In invaded HLWF, native seedling regeneration is hindered, and restoration efforts should focus on non-native understory removal.

La dinoflagellata bentonica Ostreopsis cf. ovata causa fioriture lungo le coste del Mediterraneo, spesso associate a intossicazione dei bagnanti e a morie di organismi marini dovuti alla produzione di palitossine. È stato studiato il ciclo vitale di O. cf. ovata allo scopo di valutare se la riproduzione sessuata avviene in omo e/o in eterotallia. Questa avveniva in entrambe le condizioni, sebbene l’eterotallia sembri essere la via favorita. La limitazione di nutrienti sembra stimolare gli stadi sessuali. Sono stati identificati diversi morfotipi: gameti, planozigoti, stadi della maturazione dell’ipnozigote, e cisti temporanee. La fusione dei gameti avviene seguendo due meccanismi: (i) cellule vegetative unite mediante le epiteche e (ii) gameti in fusione con i cingoli allineati lateralmente con la produzione di un planozigote biflagellato riportato per la prima volta in O. cf. ovata. L’ecologia dei bloom di O. cf. ovata è stata studiata dal 2006 al 2010 lungo la Riviera del Conero (N Adriatico) per valutare il ruolo dei parametri ambientali. Il massimo è rilevato in tarda estate (106 cell. g-1 fw). Le abbondanze erano significativamente più elevate sulle rocce rispetto alle macroalghe, suggerendo una possibile interazione tra Ostreopsis e l’ospite e nei siti riparati rispetto agli esposti, indicando che l’idrodinamismo gioca un ruolo chiave nella dinamica del bloom. Temperatura e nutrienti non sembrano avere un ruolo chiave sulla dinamica del bloom. È stata osservata un’elevata variabilità morfometrica (DV:18.5-75 μm; W:12.5-60 μm; AP: 10-31.25 μm). O. cf. ovata mostra un DV significativamente inferiore in siti riparati rispetto che in siti esposti, suggerendo che i primi siano siti favorevoli per una intensa proliferazione. Le dimensioni delle cellule di Osteopsis in colonna d’acqua erano significativamente maggiori che in quelle epifite, suggerendo che le cellule risospese in colonna derivino probabilmente da una popolazione bentonica matura.
The benthic dinoflagellate Ostreopsis cf. ovata causes massive blooms along the Mediterranean coasts, associated with noxious effects on human health and with mortality of marine organisms, due to the production of palytoxins. The O. cf. ovata life cycle was studied in order to evaluate if sexual reproduction occurred in homothallic and/or heterothallic conditions. Sexual reproduction occurred in both conditions, although heterothally seems to be the preferential way. Nutrient limitation seems to stimulate sexual stages. Different morphotypes have been identified: gametes, planozygotes, different maturation stages of hypnozygotes, and non-dormant cysts. Gamete mating occurred following two mechanisms: (i) vegetative cells joined by epitheca and (ii) gametes mating with cingula laterally aligned, producing a biflagellate planozygote, which was for observed the first time in O. cf. ovata. The ecology of O. cf. ovata bloom was investigated from 2006 to 2010 in the Conero Riviera (N Adriatic Sea) to evaluate the role of environmental factors and substratum. Maximum was always observed in late-summer (106 cells g-1 fw). Significantly higher abundances were observed on rocks than on seaweeds, suggesting that some interactions may occur between Ostreopsis and their living hosts. Hydrodynamism plays a major role in Ostreopsis blooms: abundances were significantly higher in sheltered than in exposed sites. Temperature and nutrients do not seem to have a key role on the bloom dynamics. A high morphometrical variability was shown (DV:18.5-75 μm; W:12.5-60 μm; AP: 10-31.25 μm). O. cf. ovata showed DV significantly lower in sheltered sites compared with exposed ones, suggesting that the former represent favorable sites for intense O. cf. ovata proliferation. The dimensions of Ostreopsis cells in the water column were significantly higher than those of epiphytic ones, suggesting that resuspended cells in the water column probably derived from a mature benthic population.

Insufficient sleep duration is associated with poor physical and mental health outcomes, and many Americans report that they are not meeting sleep duration recommendations. Many individuals choose to restrict their own sleep, yet little is known about the source of this sleep deficit. Recent research efforts have used the Theory of Planned Behavior (TPB) to predict sleep health behavior. However, this research is limited in that it fails to measure volitional sleep behavior and focuses exclusively on between-person differences. This study addressed these limitations by using an intensive longitudinal design to test how constructs of the TPB relate to nightly sleep opportunity. Healthy college students (N=79) completed a week long study in which they completed 4 ecological momentary assessment signals per day that measured their attitudes, perceived norms, perceived behavioral control (PBC), and intentions relating to their nocturnal sleep opportunity. Participants wore an actiwatch each night of the study to measure their sleep opportunity. Analyses revealed between- and within-day variability of attitudes, perceived norms, PBC, and intentions. Further, there were significant between- and within-day trajectories of these constructs. Mixed linear models demonstrated that both intentions and PBC were significant predictors of subsequent sleep opportunity, and that PBC was the strongest predictor of future intentions. The between-and within-day patterns of these constructs highlight important considerations for their measurement, and provide insight into the potential refinement of sleep promotion efforts. Results also demonstrate that within-person changes in PBC and intentions predict subsequent sleep opportunity, demonstrating the need for a daily framework when using the TPB to predict sleep health behavior.