Tesi sul tema "Macroalgae communities"

>Magister Scientiae - MSc
Marine macroalgae are known to carry diverse bacterial communities which interact with their hosts in both harmful and beneficial ways. Algae hosts provide the bacteria with a rich source of carbon in the form of carbohydrate polysaccharides such as fucoidan, agar and alginate, which the bacteria enzymatically degrade. Splachnidium rugosum is a brown alga (Phylum: Phaeophyta) that grows exclusively in the Southern Hemisphere along the temperate shores of South Africa, New Zealand and Australia. While several studies have investigated S. rugosum distribution and fucoidan production, the microbiome of S. rugosum remains largely uncharacterized. Thus, the major objective of the present study was to isolate, identify and characterize epiphytic bacterial communities associated with S. rugosum. Algae were sourced from Rooi Els (Western Cape, South Africa) during winter 2012. Culture based methods relied on a range of selective marine media including marine agar, nutrient sea water agar, nutrient agar and thiosulfate-citrate-bile-salts-sucrose agar to determine the composition and uniqueness of bacterial communities associated with S. rugosum. Epiphytic isolates were identified to species level by 16S rRNA gene sequence analysis and encompassed 39 Gram-negative and 2 Grampositive bacterial taxa. Isolates were classified into four phylogenetic groups, Gamma - Proteobacteria, Alpha-Proteobacteria, Firmicutes and Bacteriodetes. Bacteria belonging to the phylum Gamma-Proteobacteria were the most abundant, with Vibrio and Pseudoalteromonas being the dominant genera. Three isolates with low sequence identity (˂97%) to their closest relatives could possibly represent novel species. These isolates were grouped into the genera Shewanella, Sphingomonas and Sulfitobacter. All bacterial isolates (41) were screened for antimicrobial activity against the following test strains: Escherichia coli, Bacillus cereus, Staphylococcus epidermidis, Mycobacterium smegmatis Micrococcus luteus and Pseudomonas putida. Fifteen isolates (36%) displayed antimicrobial activity against one or more of the test strains, while one isolate (Pseudomonas species) showed broad spectrum antimicrobial activity against all the test strains except for E. coli. This study provides the first account of the diversity and composition of bacterial populations on the surface of S. rugosum, and demonstrates the ability of these bacteria to produce antimicrobial compounds. Despite recent advances in metagenomics, this study highlights the fact that traditional culturing technologies remain a valuable tool for the discovery of novel bioactive compounds of bacterial origin.

Ocean acidification has the potential to profoundly affect marine ecosystems before the end of this century, but there are large uncertainties on its effects on temperate benthic communities. Volcanic CO2 seeps provide an opportunity to examine and improve our understanding of community responses to ocean acidification. In this thesis, two Mediterranean CO2 seeps (Methana in Greece and Vulcano in Italy) were used to investigate the responses of macroalgae and their epifaunal communities to increased CO2. Changes in plant-herbivore interactions at elevated CO2, as well as adaptation potential of dominant macroalgae and responses of macroalgae and epifauna to concurrent exposure to elevated CO2 and copper pollution, were also examined. Firstly, I determined that volcanic seeps off Methana (Greece) are suitable for ocean acidification studies as they do not have confounding gradients in temperature, salinity, total alkalinity, nutrients, hydrogen sulphide, heavy metals or wave exposure. Calcifying macroalgae abundance decreased as CO2 increased both at Methana and at Vulcano, while fucoid algae seemed to benefit from elevated pCO2 levels. Seasonality greatly affected macroalgal responses to increasing CO2, according to the annual cycles of dominant species. Epifaunal communities of dominant fucoid algae changed at elevated pCO2 as well, with calcifying invertebrates decreasing and polychaetes increasing near the seeps. Herbivore control of macroalgal biomass did not greatly change at elevated pCO2 levels, as limpets had a minor role in controlling macroalgal biomass off Vulcano (Italy) and sea urchins were replaced by herbivorous fish near seeps off Methana. The two macroalgal species examined for signs of long-term acclimatisation (Cystoseira corniculata (Turner) Zanardini and Jania rubens (Linnaeus) J.V.Lamouroux) to ocean acidification using reciprocal transplants did not appear to have permanently acclimatised to elevated pCO2 levels, but changed their physiology in four to nine months depending on the local environment. Furthermore, when exposed to a 36-hour copper pulse at elevated pCO2 levels both seaweed species accumulated more copper in their tissues compared to those exposed to copper in reference pCO2 conditions, and this resulted in altered epifaunal assemblages on C. corniculata. These observations suggest that benthic communities will significantly change as CO2 levels increase, and that long-term acclimatisation is not likely to play a significant role; this would have profound consequences for benthic ecosystems and the services they provide.

Human impacts on ecosystem health and functioning are an important and increasing problem for marine ecosystems. In order to properly implement effective management techniques for the amelioration or reversal of these impacts, we require accurate information regarding the degree to which these systems vary naturally and what factors primarily drive this variability. Further, understanding where the influence of particular management interventions rank relative to other potential drivers of community structure is important in understanding potential and realised management success. In addition, it is likely that different factors, and therefore different disturbances and management interventions, will have different effects for different ecosystem components. On coral reefs, phase shifts to less desirable macroalgal dominated states are often an indicator of changes in ecosystem functioning driven by either overfishing or nutrient enrichment, or both. N a-take marine protected areas (MPAs) have been shown to reverse some of these effects, but cannot prevent the diffusion of nutrients or sediments across their boundaries. In this thesis, I assess the scale and drivers of variability within benthic communities and fish communities within and outside no-take MPAs in the marginal coral reef habitats of Moreton Bay in subtropical eastern Australia. I focus on the interaction between macroalgae and herbivorous fish and hypothesise that by determining the drivers operating on these components of the marginal reef habitat, I might be able to ascertain the potential for MPAs to elicit community-wide change.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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The study evaluated the effects of herbivory pressure, nutrient availability and potential propagule supply on recruitment and succession of coral reef macroalgal communities. Recruitment and succession tiles were placed in a nutrient-herbivory factorial experiment and macroalgal abundances were evaluated through time. Proportional abundances of macroalgal form-functional groups on recruitment and succession tiles were similar to field established communities within treatments, evidencing possible effects of adult macroalgae as propagule supply. Macroalgal abundance of recruitment tiles increased with nutrient loading and herbivory reduction combined whereas on succession tiles nutrient loading increased abundance of articulated-calcareous only when herbivores were excluded. Macroalgal field established communities were only affected by herbivory reduction.

This thesis focuses on intertidal seaweed communities on rocky shores and was planned to provide solid scientific background for the application of the EU Water Framework Directive (WFD) to the Azores based on the tool developed for British shores. The main structuring factors for rocky shore intertidal communities are briefly described and characterized for each of the two regions. Rocky shore intertidal seaweed communities of the British Isles and the Azores are compared based on presence/absence data recorded in single occasion visits to individual stretches of shore. The existing numerical indices used for the assessment of ecological quality for the WFD in the British Isles and in northern Spain have been tested for Azorean shores and adaptations proposed in order to incorporate differences between regions. A new alternative index is proposed for the Azores and possibly for remaining Macaronesian archipelagos that combines features used in the British Isles and in northern Spain. A first account is given of seaweed communities and their ecological quality classification at two rocky shores affected by shallow water hydrothermal activity. In the Azores, this is the closest to polluted shores, with which to test quality assessment tools. The accumulation of heavy metals in different seaweeds has been quantified and compared between the vicinity of shallow water hydrothermal activity and of urban development in the Azores. The concentration of heavy metals in Fucus spiralis has been compared between samples affected by hydrothermal seeps in the Azores and by acid mine drainage in the British Isles. Preliminary culture experiments provide an insight on the influence of temperature and acidity on the growth and photosynthesis of F. spiralis, as measures of metal accumulation capacity of this species.

Algal blooms have caused significant losses in seagrass and macroalgae in the Indian River Lagoon, FL. To gain an understanding of these effects, samples of Gracilaria sp., Halodule wrightii, pinfish, and white mullet were taken throughout October and November of 2013. Samples from 2001 of Gracilaria sp., Halodule wrightii, Syringodium filiforme, Thalassia testudinum, pinfish, spotted seatrout, and white mullet were also obtained. Stable isotope data were obtained from these samples and compared by year and species. Halodule wrightii and pinfish had a significantly larger 2013 [delta]C13 values. Halodule wrightii also displayed lower total %C and total %N averages for 2013 when compared to 2001 data. These results may indicate a link between Halodule wrightii and pinfish, with pinfish consuming organisms that use Halodule wrightii as their source of nutrients. The location of collections also seemed to play a role in stable isotope values, as indicated by samples of Halodule wrightii.
B.S.
Bachelors
Biology
Sciences

The growth and accumulation of macroalgae in estuaries are a common sight throughout the world (Boyer and Fong, 2005). Because macroalgae establish such complex but important links with other components within an estuary, it is essential to know which variables control and regulate their occurrences. The type of algae that will occur in an estuary depends however, on the physical and chemical features of the particular estuary (Lobban and Harrison, 1994). The focus of this study was to document and provide a listing of algae from estuaries around the Eastern Cape coast of South Africa and describe the communities which form within each estuarine habitat. The questions posed were: Do algae assemblages differ in estuaries with different environmental conditions? Are different plant communities inhabited by different algae communities? Also, are algae diverse in estuaries that are in a pristine condition? The estuaries were Mngazana, Ngqusi/Nxaxo, Mtati, Mpekweni, East Kleinemonde, West Kleinemonde, Kariega, Bushmans, Kowie and the Sundays estuary. Percentage cover surveys were conducted and environmental parameters recorded to determine community structure of algae and their environmental tolerances. A total of 49 different macroalgal species were identified from 11 estuaries, which were dominated by Chlorophytes (23 species) and Rhodophytes (17 species). The Ochrophytes consisted of 10 species. The highest number of species recorded was 29 at the Bushmans estuary (March 2009), while the lowest number (4 species) was recorded at Mtati (October 2008). Common Chlorophytes found included Ulva prolifera, Chaetomorpha linum and Codium tenue. In the Division Ochrophyta, species from the Genus Ectocarpus were the most common. Of the red algae filamentous reds, Polysiphonia incompta and Polysiphonia kowiensis were the common algae found at estuaries. Salinity (p= 0.029861; n= 49) and temperature (p= 0.037641; n= 49) were the driving environmental parameters of estuaries and significantly influenced richness of species. In ordination analyses, patterns of biogeographic distribution were noticeable and were described by salinity. Four gradients caused by salinity were therefore found – which is inversely correlated to water clarity. Moreover, a clear split between temporarily open/closed and the permanently open estuaries was observed. Samples grouped into four communities presumably based on the similarity in conditions of estuaries. Within each estuarine community and major type of estuary there was a range of environmental conditions. However, the macroalgae within each community may not have been colonists of or found in greatest abundances in the estuaries of these communities per se, but may have grouped together in this manner based on the optimum growing conditions for them. Also, specific algal groups were not directly determined by the type of estuary they were found in; they were driven by environmental ranges rather. The results therefore support hypothesis one which states species distribution and diversity differ and are influenced by environmental gradients of the estuary. Although close species and habitat relationships were apparent from the ordination analyses, providing support for hypothesis two which states “Different plant communities in estuaries will be inhabited by different macroalgae communities”, the evidence was not substantial enough to provide sufficient support for the hypothesis. Lastly, the hypothesis “Macroalgae are diverse in estuaries that are in a pristine condition” was not accepted as highest species numbers were found in estuaries of greatest anthropogenic disturbance (e.g. Bushmans estuary) and not in estuaries which where ecologically more natural (e.g. Mtati estuary). By doing monthly macroalgal sampling over a period of one year for example one would obtain greater information of biodiversity, and patterns of macroalgal seasonality may be uncovered as well. This is an area of reasearch which needs to be investigated in the future as it would greatly add to the understanding of the role macroalge have in an estuarine environment.

Cette thèse vise à quantifier et à expliciter les effets de l’hydrodynamisme sur les biocénoses des estrans rocheux du Nord-Est Atlantique. Dans cette optique, plusieurs études ont été menées sur 14 sites de la pointe bretonne, à différentes échelles spatiales, de quelques mètres à une centaine de kilomètres. Pour étudier les variations de la structure des communautés de macroalgues et des assemblages à dominance macroalgale, deux méthodes d’échantillonnage biologique ont été utilisées pour la macroflore et la macrofaune. Un nouveau proxy de l’hydrodynamisme à petite échelle a été développé, la hauteur de vague in situ. La hauteur de vague in situ apparaît comme le facteur physique le plus important dans la structure interne des communautés macroalgales. En étudiant la différentiation de six communautés de macroalgues étagées sur l’estran, le rôle de l’hydrodynamisme semble mineur par rapport à l’élévation et à la durée moyenne d’émersion. Le passage des assemblages intertidaux d’une dominance macroflore à une dominance macrofaune est essentiellement expliqué par la hauteur de vague in situ. Les organismes sessiles répondent de façon différente à l’hydrodynamisme. De plus, l’existence de seuils de tolérance à l’hydrodynamisme a été mis en évidence. Au sein des assemblages dominés par les macroalgues, la hauteur de vague in situ module de façon significative les interactions faune-flore, fortes en haut et au milieu d’estran, et flore-flore, plus importantes en bas de la zone intertidale. L’étude de l’effet de l’hydrodynamisme sur une communauté macroalgale de milieu d’estran à l’aide de sept estimateurs (proxys) a révélé des réponses de la communauté différant selon l’estimateur. Les hauteurs de vague mesurées in situ et calculées selon le modèle SWAN semblent complémentaires pour évaluer le rôle de l’hydrodynamisme dans la structure des écosystèmes intertidaux rocheux à dominance macroalgale
This thesis aims at quantifying and explaining the effects of hydrodynamics on the communities of the North-East Atlantic rocky shores. In that prospect, several studies were carried out in 14 sites at the western head of Brittany, at different spatial scales, from a few metres to a hundred kilometres. Two biological sampling methods were used for macroflora and macrofauna to study variations in the structure of macroalgal communities and seaweed dominated assemblages. A new proxy for small-scale hydrodynamics has been developed, in situ wave height.In situ wave height appears to be the most important physical factor in the internal structuring of macroalgal communities. By studying the differentiation of six macroalgal communities vertically distributed on the shore, the role of hydrodynamics seems to be minor compared to the elevation and the average duration of emersion.The shift in intertidal dominance from macroflora to macrofauna is mainly explained by in situ wave height. Sessile organisms respond differently to hydrodynamics. Interestingly, the existence of tolerance thresholds for hydrodynamics was highlighted. Within the communities dominated by macroalgae, the in situ wave height significantly modulates both the fauna-flora interactions, strong at the top and middle of the shore, and the flora-flora interactions, more important at the bottom of the intertidal zone.Studying the effect of hydrodynamics on a midintertidal macroalgal community using seven proxies revealed different community responses. The wave heights measured in situ and calculated using theSWAN model appear to be complementary in assessing the role of hydrodynamics in the structuring of macroalgal-dominated rocky intertidal ecosystems

Macroalgae are abundant on shallow temperate reef environments, often forming complex communities that comprise several strata. In southern Australia, these assemblages are dominated by large canopy forming taxa from the Orders Laminariales and Fucales. The presence of subtidal fucoid macroalgae differentiates these communities from that elsewhere, and emphasises the need for local studies rather than relying on generalisations made elsewhere. Like most natural systems, temperate reefs are often threatened by human activity with degradation reported from many locations in close proximity to urban settlements. The work presented in this thesis involves an examination of the temporal and spatial variability in the structure of macroalgal communities from reefs along the Adelaide (South Australia) metropolitan coast. The work looked specifically at the effects of a dispersed sediment plume, resulting from the 1997 beach sand-replenishment dredging program, on shallow sub-tidal reef systems. An examination of the structure of canopy forming phaeophycean macroalgae in Gulf St Vincent (South Australia), noted large amounts of both spatial and temporal heterogeneity. Notwithstanding, this variation was not random, but demonstrated considerable structure that could be linked to a number of important underlying processes. In particular, macroalgal assemblages appeared as a mosaic of patches, each of which comprised a high-density state clearly dominated by a single genus (Cystophora, Sargassum, or Ecklonia), or alternatively a lower density mixed assemblage (Variable Low Abundance, VLA). Macroalgal community structure appeared to be driven by biotic interactions at small scales (metres), such that patches comprised of different species of algae in high density states rarely abutted one another. Instead, VLA assemblages frequently formed a buffer being situated between these mono generic patches. In terms of successional processes, the high-density states appeared to be relatively stable whereas the VLA state, at least in some systems, was transitory. This finding was supported by the absence of intermediary high- density states (e.g. a mix of Cystophora and Ecklonia) implying that state changes must occur via the VLA state following some form of disturbance. Larger scale patterns appeared to be driven by environmental variation, with factors such as wave exposure influencing habitat suitability for individual species and thereby affecting community composition. These phenomena were examined in terms of life history strategies that tend to promote stability, and which are common in late successional taxa. The importance of properties enhancing stability and the role of disturbance was investigated experimentally using a dispersed sediment plume, which entirely engulfed two reefs, as a pulse impact. This disturbance was of particular relevance given that degradation of macroalgal communities in close proximity to the City of Adelaide has been, at least in part, attributed to the effects of elevated levels of sediment. Follow up surveys revealed that the sedimentation from the plume had primarily affected newly recruiting individuals, with few juveniles surviving to one year of age. Over the following few years, the effect of this recruitment failure cascaded into the adult stand. In broader terms, unfavourable climatic conditions prior to the start of the study, including a particularly severe El Nino event, had a widespread effect on local assemblages, causing high levels of both adult and juvenile mortality. As such, at the commencement of the study, macroalgal communities across the study area were in the process of recovery. This was observed at control sites over the duration of the study. In contrast, recruitment failure at the sediment-affected sites retarded the recovery process, exacerbating the problems associated with prior unfavourable climatic events and leaving them in a degraded state. This study demonstrated that macroalgal assemblages are equipped (under natural conditions) to handle 'normal' environmental fluctuations (such as inter-annual variability). However, the additional stress associated with certain anthropogenic impacts has the potential to push them over the limit, causing degradation. The loss of canopy macroalgae reduces the structural complexity of the system, leading to a concomitant reduction in their ability to recover. As such, these findings are of particular relevance to those charged with the responsibility for managing near-shore marine environments. The plume was created accidentally during a dredging operation for beach sand replenishment of Adelaide's eroding shoreline.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

Les grandes algues brunes sont des espèces clés dans les écosystèmes marins des latitudes tempérées où elles forment les forêts marines, parmi les écosystèmes les plus productifs et diversifiés au monde. En Méditerranée, elles sont représentées par les espèces du genre Cystoseira sensu lato, pour la plupart endémiques et caractérisées par leur longue durée de vie et faible dispersion. Cependant, les impacts anthropogéniques causent leur régression, entrainant des changements abruptes vers des communautés moins complexes (communautés gazonnantes et déserts marins), rendant l'écosystème potentiellement plus vulnérable aux phénomènes émergents, tels que les efflorescences de microalgues benthiques nuisibles. Les efflorescences de dinoflagellés benthiques du genre Ostreopsis, se développant sur les communautés macroalgales ont augmenté au cours des dernières décennies dans les régions tempérées, y compris la Méditerranée. Elles sont connues pour leurs effets néfastes sur la santé publique, les écosystèmes et l'économie qui en dépend.Les objectifs de cette thèse sont d'évaluer (i) les causes abiotiques (température et acidification) et biotiques (herbivorie, facilitation écologique) potentiellement à l'origine de la régression des forêts marines Méditerranéennes, et (ii) les éventuelles conséquences de cette régression dans la facilitation des efflorescences d'Ostreopsis spp. Les deux premiers chapitres de cette thèse sont focalisés sur les causes de la régression de Cystoseira s.l. Dans le Chapitre 1, les effets du changement climatique et de la facilitation écologique sur le recrutement de Cystoseira compressa ont été étudiées par des expériences en laboratoire. Un effet interactif du réchauffement et de l'acidification de l'océan, qui affecte négativement les recrues de C. compressa, a été observé, ainsi qu'un effet négatif de la présence d'algues corallines incrustantes. Dans le Chapitre 2, la pression herbivore de différents invertébrés sur les recrues de C. compressa a été étudiée par des expériences sur le terrain et en laboratoire. Les résultats montrent une forte pression herbivore de plusieurs espèces d'invertébrés (mollusques, décapodes et isopodes) sur les recrues de C. compressa, qui pourraient représenter une menace pour les populations à long terme et une cause d'insuccès des actions de restauration.Les chapitres 3 et 4 se focalisent sur le lien entre la perte de forêts marines et les efflorescences d'Ostreopsis spp. Dans le Chapitre 3, une revue bibliographique s'intéresse au rôle de l'habitat dans la facilitation/régulation des efflorescences. Malgré un évident manque d'informations à l'échelle globale sur les méso- et macro-habitat plus propices aux efflorescences, les connaissances actuelles démontrent que les substrats les plus échantillonnés pour étudier ces espèces sont des macroalgues formant des communautés peu complexes, suggérant que ces communautés hébergent les efflorescences les plus importantes. Dans le Chapitre 4, la relation entre les efflorescences d'Ostreopsis et les communautés macroalgales a été étudiée par des expériences sur le terrain en Italie et en France. Des différences significatives ont été observées sur un des deux sites d'étude tandis que dans le deuxième on estime que la forte variabilité puisse avoir caché les éventuelles préférences d'Ostreopsis spp. Mais, des études à plus grande échelle seraient nécessaires pour conforter ces résultats.Les résultats de cette thèse représentent d'importantes avancées sur les causes et les effets de la régression des forêts de Cystoseira s.l., confortant l'importance de leur conservation et (où nécessaire) restauration, en contribuant à la conception de stratégies de gestion, non seulement pour préserver un des écosystèmes les plus productifs en Méditerranée, mais aussi dans le but de limiter d'éventuelles conséquences inattendues, telles que les efflorescences d'Ostreopsis spp
Large brown forest-forming macroalgae are dominant foundation species, ecosystem engineers of marine macroalgal forests. In the Mediterranean Sea, they are mainly represented by Cystoseira sensu lato spp. most of wich are endemic. They are also characterized for being long-lived species with short dispersal of the zygotes. Marine forests are one of the most productive and diverse ecosystems on earth. However, anthropogenic impacts are pushing them to the edge, causing regime shifts towards less complex communities such as shrubs, turfs, or even barren grounds. Marine forest loss affects the whole ecosystem, eventually making it more vulnerable to emergent phenomena such as benthic harmful algal blooms (BHAB). BHAB of the genus Ostreopsis spp. have been expanding in recent decades through temperate regions such as the Mediterranean Sea, where they have important public health, ecological and economic consequences. Major blooms are generally observed on macroalgal turfs and shrubs, suggesting that less structurally complex macroalgal communities could have an active role in promoting the proliferation of blooms.The main objectives of this thesis are (i) to assess some abiotic (climate change) and biotic (herbivory) causes of marine forests loss in the Mediterranean Sea and (ii) the potential consequences this loss can have in the context of BHABs proliferation. In the first two chapters, the causes of Cystoseira s.l. spp. loss were assessed. In Chapter 1, the effects of climate change and species facilitation on the recruitment of Cystoseira compressa were studied in controlled laboratory experiments. The major results from this chapter show that the interactive effects of ocean warming and acidification negatively affect C. compressa recruits, which are also negatively affected by the presence of crustose coralline algae. In Chapter 2 the grazing pressure and the effects of different invertebrates on recruits of C. compressa were assessed through field surveys and both field and laboratory-based experiments. The results obtained show a high grazing rate of several common invertebrate species (molluscs, decapods et isopods) on recruits of C. compressa, representing a threat to natural populations in the long term, but also affecting the success of restoration actions. In chapters 3 and 4 the consequences of forest loss and in particular, the facilitation of Ostreopsis spp. blooms was approached by a literature review and field experiments. The review, reported in Chapter 3, focussed on the role of habitat in the facilitation of Ostreopsis spp. blooms. Despite an evident lack of information at the global scale on the meso- and macro-habitat fostering Ostreopsis spp. blooms, the present knowledge suggests a relationship between the abundance of Ostreopsis spp. and the complexity of the macroalgal communities. In Chapter 4 Ostreopsis spp. blooms have been studied in relation to macroalgal communities in field experiments in Italy and in France. A high variability on Ostreopsis spp. abundances was observed in the different macroalgal species and communities sampled, in some cases likely hiding other potential patterns of Ostreopsis spp. preferences. Larger scale studies would be needed to confirm these results.These findings provide important insights into the causes and effects of Cystoseira s.l. spp. loss and are of major interest for the conservation of Mediterranean marine forests, contributing to the development of effective management measures. The results presented support the importance of marine forests restoration in the Mediterranean Sea, as recommended by the 2030 European Biodiversity Strategy, the United Nations Decade on Ecosystem Restoration and the 2030 Agenda for Sustainable Development objectives. Such restoration actions will not only increase the productivity and biodiversity of coastal ecosystems but could potentially mitigate the public health, ecological and economic consequences of Ostreopsis spp. blooms

Les proliférations de microalgues peuvent être nocives. L'augmentation récente de la fréquence et de l’étendue géographique des efflorescences de dinoflagellés benthiques toxiques comme Ostreopsis cf. ovata peut poser de réels problèmes de santé publique. La côte méditerranéenne Nord-Occidentale (lieu de cette étude) est l'une des nombreuses régions méditerranéennes où les proliférations d'algues nuisibles représentent une menace pour l’économie touristique. Dans les années à venir, une attention particulière devra être portée à la gestion et la prévision des proliférations de ces microalgues nuisibles benthiques et c'est dans ce contexte que cette étude a été menée. Une étude bibliographique portant sur les proliférations d’Ostreopsis spp. indique un manque important de données en relation avec l'écologie d’O. cf. ovata, en particulier concernant les substrats biotiques, ainsi que les communautés les habitats benthiques et, par conséquent, les rôles éventuels que ceux-ci peuvent jouer en tant que stimulateurs majeurs des efflorescences d’Ostreopsis spp. Durant les étés 2015 et 2016, des expériences in situ de courte durée ont été menées sur les récifs côtiers et ont été complétées par des expériences en laboratoire. Les résultats obtenus ont permis d’établir que quatre communautés distinctes de macroalgues abritent des abondances différentes d’O. cf. ovata. En particulier, les abondances les plus élevées ont été enregistrées dans des sites dominés par des structures communautaires peu complexes ; Turf et Dictyotales, alors que les sites dominés par des communautés complexes de Cystoseira n’ont montré aucune prolifération significative de microalgues. Ces résultats impliquent que les régions côtières dominées par les communautés composées de Cystoseira spp. pourraient potentiellement réduire les proliférations de Ostreopsis spp. En outre, d’autres facteurs abiotiques, tels que les concentrations en nutriments et métaux traces, ne contribuent pas (ou peu) à expliquer la dynamique des populations de O. cf. ovata. Les multiples facteurs de stress d’origine anthropique continueront à influencer le fonctionnement de l’écosystème marin. La compréhension de ces impacts et la façon dont ils influencent la dynamique des dinoflagellés benthiques toxiques est impérative pour prévoir, gérer et éventuellement réduire ces proliférations, à l’échelle de l’océan mondial
Algal blooms can be harmful. The global management and forecasting of benthic harmful algal blooms (BHABs) will be of increasing importance in the years ahead and that is what this study sets out to address. The increase over recent decades, in both frequency and geographical range, of the potentially harmful benthic dinoflagellate Ostreopsis cf. ovata can pose real problems for human health. The French Côte d’Azur, the location for this study, is just one of many Mediterranean areas where harmful algal blooms pose a potential economic threat to a tourist-based economy. A review of the existing literature on Ostreopsis spp. blooms shows a severe lack of information about the ecology of O. cf. ovata in relation to biotic substrates, communities and habitats and thus any possible roles these may play in fostering major Ostreopsis spp. blooms. Through a series of in situ experiments on temperate reefs on the Côte d’Azur over the summers of 2015 and 2016 with follow-up experiments in the laboratory, this study establishes that four distinct macroalgal communities harbour different O. cf. ovata abundances. The results indicated that higher abundances were recorded in sites which were dominated by less complex community structures; Turf and Dicyotales, while sites with Cystoseira spp. communities present did not harbour significant microalgal blooms. These results imply that coastal regions with a dominance of Cystoseira-composed-communities could potentially be less prone to blooms or even inhibit Ostreopsis spp. proliferation. Although, no clear relationship was found between inorganic nutrient concentrations and O. cf. ovata abundances, it was observed that in the bloom onset period, nitrogen compounds were higher than in the rest of the study period (both in 2015 and 2016). Multiple human stressors will continue to impact marine vegetation, understanding these impacts and how they then influence bloom dynamics is imperative for the global management and mitigation of BHABs

This study examines the influence of intertidal macroalgae on sediment accumulation, and the effect of sediment cover on intertidal community structure. Three shores on the North Yorkshire coast, England, were used to investigate differences in the quantity of sediment trapped by ten morphologically different algal species, and the relationship between morphology and the quantity of sediment trapped. The quantity of sediment accumulated in quadrats of four different macroalgal communities (canopy, turf, canopy/turf and bare rock) was also examined. Differences in sediment cover and community structure were investigated on the intertidal rocky shore at Holbeck, North Yorkshire. The distribution and position of both were described using transects across three sites, whilst relationships were examined using 54 fixed quadrats in the mid shore. Across three different shores the mass of dried sediment g⁻¹ macroalgal dry mass was found to differ between macroalgal species. All measured aspects of macroalgal morphology correlated with the quantity of sediment trapped. Macroalgae with different morphologies trapped different gram size compositions but no differences were found hi the quantity of sediment accumulated by turf, canopy, bare rock or unmanipulated algal communities. At three different sites at Holbeck, the site with the greatest sediment cover had lower macroalgal species diversity, richness and total abundance, patellid and littorinid abundance. Although differences were found in sediment cover between sites in the mid shore, no differences were found hi community structure. Sediment cover had negative correlations with macroalgal richness and diversity in algal quadrats, but positive correlations with macroalgal abundance and diversity in bare rock quadrats. Within individual macroalgae morphology was found to affect the quantity of sediment trapped, however at quadrat level macroalgal morphology had no effect. At both the level of the quadrat and the whole shore sediment cover influenced community structure, whilst within the mid shore alone sediment cover did not affect community structure. This work suggests that relationships/interactions between sedimentation and intertidal community structure are scale dependent.

As human activity along coastlines increase, degradation and destruction of coastal marine ecosystems around the globe will increase at an alarming rate. In an effort to mitigate degradation and destruction of coastal marine ecosystems, artificial reefs have been used in restoration and enhancement projects. As artificial reefs are the main method of restoring diversity to a degraded area, it is important to know the mechanisms that drive marine community assembly and diversity on those reefs. Understanding community assembly patterns of foundational species, in particular, may provide insight to community assembly patterns at higher trophic levels. Subtidal macroalgae are commonly seen as foundational species in marine environments and both deterministic and stochastic processes play a role in their assembly. Environmental gradients, which are deterministic processes, play a significant role in structuring subtidal macroalgae communities. Depth, which is negatively correlated with light, is the main driver structuring subtidal macroalgal communities, however, other gradients such as water flow, and distance to a propagule source also impact their assembly. This study sought to determine which environmental gradients play a prominent role in subtidal macroalgal community assembly. To study subtidal macroalgal community assembly, 92 artificial reef units called Reef Balls were deployed east of the Ogden Point Breakwater in Victoria, BC in June 2009. Two years passed to allow for macroalgal growth and early successional processes to occur prior to sampling the communities on thirty Reef Balls via underwater collection in July 2011. Algae were sorted by genus and dry weight was measured. To determine effects of environmental gradients on community assembly light, depth, water flow, distance to the nearest Reef Ball and distance to the breakwater were measured at each Reef Ball. A redundancy analysis revealed that depth was the most significant environmental gradient shaping algae communities and had the greatest effect on upper canopy algae. Spatial plots reveal a depth and coastline zonation of algae genera comprising the canopy. While depth was found to significantly structure algae genera found in the canopy, there was a high degree of unexplained variation in the model. This suggests that unmeasured variables such as colonization and priority effects may be driving algal community structure in the lower canopy. Differences in community structure between upper and lower canopy reveal that multiple mechanisms are responsible for shaping subtidal algal communities. Further study is required to determine the importance of stochastic colonization events and priority effects.
Graduate
0329
vmucciar@uvic.ca

Estuaries have been favoured for human settlement, and since then have slowly deteriorated as a consequence of multiple and interacting anthropogenic impacts in their unique sheltered environments. The capacity to predict which urban impacts are most severely affecting benthic communities is essential for estuarine biological conservation. Understanding urban effects and key biological responses may help to determine where impacts take place, if effects are reversible, and how pollution affects flow through the estuarine ecosystem. In this thesis, I apply observational surveys and experimental manipulation to examine patterns in sessile communities in the marine component of estuaries, and to link changes in the ecosystem to pollution sources. In one of the first studies to consider large scale patterns of rocky reef communities across multiple estuaries, I investigated the influences of environmental and anthropogenic factors in influencing the composition, cover and dominance of macro-algae and sessile invertebrates. Reef Life Survey underwater transect protocols were conducted in three large urban estuaries. I utilised information from photo-quadrats to disentangle natural and human impact variables and describe an environmental baseline for current sessile community patterns within these ecosystems. Statistical model selection was conservative, with environmental variables entered into the models first, and then human effects accounted for. I then tested for significant patterns for functional groups. Heavy metals and proximity to ports appeared to be the major anthropogenic drivers of patterns of temperate reef sessile biota, with functional group response consistent and generalizable for two of the three estuaries. Comparison between the three capital city estuaries highlighted a clear effect of intense urbanisation and the complex nature of historical and contemporary pollution effects on biota. To further disentangle the effects of different pollution types on sessile reef assemblages, I conducted a manipulative experiment in one of the most heavily polluted estuaries worldwide (Derwent Estuary, Hobart). I translocated healthy sessile communities grown on concrete pavers to locations adjacent to marinas, sewerage outfalls, fish farm cages, and stormwater discharges, each with associated controls. Reef communities subjected to chronic levels of pollution in the most heavily urbanised area differed from those outside this area, with perennial Laminariales largely replaced by stress-tolerant species. Pollution types differed in their effects on transplanted communities, with marinas showing greatest negative impact, with significant losses in canopy and foliose macroalgae. Communities near fish farms, marinas and storm water drains were characterised by abundant filamentous algae. A concurrent experiment using bare pavers assessed the effects of the four different pollution sources on recruitment of native and non-indigenous algae and sessile invertebrates on rocky reefs in the degraded Derwent estuary over a one year period. Non-indigenous and cryptogenic species showed significantly higher cover on experimental pavers near marinas and sewerage drains compared with associated control sites. The cover of opportunistic species was significantly higher near fish farms and sewerage outfalls, and the cover of some native species was amplified at sewerage outlets relative to the control sites. Colonisation of less desirable algal communities seems to be accelerated by some urban impacts. Results suggest that careful consideration of urban drainage is required to reduce introductions of invasive algal species. Redirection of outlets offshore into better flushed areas and relocation of dense fish farm leases away from partially enclosed areas may help reduce some of the negative changes to sessile communities. Impacts of urban pollution on benthic assemblages can be direct or indirect, through ecological interactions. I analysed invertebrate macro and mesograzer abundances from pavers used for the reef transplantation experiment to explore the potential mediation of pollution impacts through effects of pollution on mobile fauna. Log response ratios and structural equation modelling indicated that observed responses of algal groups and grazers were directly affected by pollution, rather than through trophic pathways involving interactions between these groups. Overall, this study provides important information to improve management in estuarine systems with macroalgal-dominated reefs. Urbanisation has clearly led to large-scale decline in abundance of ‘healthy’ sessile benthic species, with persisting species presumably living near their tolerance limits. Current pollution loads need to be minimised if we are to maintain and restore the unique and undervalued reef communities in the increasingly urbanised environment of estuaries.

PhD Marine Biology
This thesis focuses on intertidal seaweed communities on rocky shores and was planned to provide solid scientific background for the application of the EU Water Framework Directive (WFD) to the Azores based on the tool developed for British shores. The main structuring factors for rocky shore intertidal communities are briefly described and characterized for each of the two regions. Rocky shore intertidal seaweed communities of the British Isles and the Azores are compared based on presence/absence data recorded in single occasion visits to individual stretches of shore. The existing numerical indices used for the assessment of ecological quality for the WFD in the British Isles and in northern Spain have been tested for Azorean shores and adaptations proposed in order to incorporate differences between regions. A new alternative index is proposed for the Azores and possibly for remaining Macaronesian archipelagos that combines features used in the British Isles and in northern Spain. A first account is given of seaweed communities and their ecological quality classification at two rocky shores affected by shallow water hydrothermal activity. In the Azores, this is the closest to polluted shores, with which to test quality assessment tools. The accumulation of heavy metals in different seaweeds has been quantified and compared between the vicinity of shallow water hydrothermal activity and of urban development in the Azores. The concentration of heavy metals in Fucus spiralis has been compared between samples affected by hydrothermal seeps in the Azores and by acid mine drainage in the British Isles. Preliminary culture experiments provide an insight on the influence of temperature and acidity on the growth and photosynthesis of F. spiralis, as measures of metal accumulation capacity of this species.
FCT - Fundação para a Ciência e Tecnologia (SFRH/BD/27466/2006)

Coral reefs are priority habitats which are vulnerable to natural and anthropogenic disturbances. These can cause phase shifts from coral habitat to degraded algal-dominated states – and consequent changes in the distribution, abundance and activity of associated fish species. In the eastern Red Sea, human-induced reef degradation is likely to increase with planned development of the Saudi Arabian coast and the changing climate. The present study therefore investigates the ecological effects of coral-algal phase shifts in reef-associated fish communities, using naturally occurring within-reef benthic zones as proxies for levels of habitat health - with a focus on how these responses differ temporally. These zones were dominated by: hard coral (coral zone), coral and turf algae (transition zone), and macroalgal canopies (algal zone). Six inshore reef areas, were studied in periods with low and high densities of Sargassum in the algal zones (May and November respectively). Community composition was assessed via visual census and predation activity predicted using two proxies: in situ experiments and biomass of carnivores. In both periods, we observed distinct fish communities in each zone - with reduced species richness, Shannon-Wiener diversity and predation intensity, from the coral to the algal zones. Decreases in the abundance and biomass of fish also occurred from the coral to algal zones in May but a spike, as well as a shift in community composition, occurred in the algal zone in November. This shift is attributed to the vast increases in grazer biomass, predominantly Siganus luridus, associated with the November bloom of Sargassum canopies. The present study established, the composition and functioning of Red Sea fish communities is spatially and temporally affected by increased macroalgal dominance. This finding supports the need for herbivorous fish to be made a conservation priority in the management and conservation of reef systems in order to prevent phase shifts to algal dominated states. We conclude that if Red Sea reefs are allowed to shift to alternate states, depending on the density of macroalgal canopies, reefs may support high biomass and abundance of fish but the functioning of the fish community will be altered and the diversity lost.

Stella Fulton investigated the impact of removing macroalgae from degraded inshore reefs around Magnetic Island. She found that periodically removing macroalgae over three years led to significantly higher coral cover and reduced re-growth of macroalgae. Macroalgal removal may therefore be an effective strategy to assist coral recovery on degraded reefs.

Bibliography: leaves 191-225.
2 v. : ill. (some col.), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The temporal dynamics of eight subtidal mixed macroalgal communities were quantified. The results were discussed in terms of the implications for sampling programs in the future and the reliability of previous work.
Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?

Bibliography: leaves 191-225.
2 v. : ill. (some col.), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The temporal dynamics of eight subtidal mixed macroalgal communities were quantified. The results were discussed in terms of the implications for sampling programs in the future and the reliability of previous work.
Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?