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Dissertations / Theses on the topic 'Aquatic invertebrates'
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Hayward, Eva. "Envisioning invertebrates and other aquatic encounters /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Peterson, Eric W. "Fate and transport of 17 [beta]-Estradiol in karst aquifers /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060131.
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Netherton, Melanie Jane. "Uptake and metabolism of pharmaceuticals in aquatic invertebrates." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/2349/.
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This thesis explored the uptake into the freshwater shrimp (Gammarus pulex) and the water boatman (Notonecta glauca) of key pharmaceuticals drawn from different therapeutic classes and covering a range of physico-chemical properties. For one compound, uptake was also assessed using the freshwater snail Planobarius corneus. In G. pulex, bioconcentration factors (BCFs) ranged from 4.6 – 185900 and increased in the order moclobemide < 5-fluoruracil < carbamazepine < diazepam < carvedilol < fluoxetine. In N. glauca BCFs ranged from 0.1 – 1.6 and increased in the order 5-fluorouracil < carbamazepine < moclobemide < diazepam < fluoxetine < carvedilol. For P. corneus, the BCF for carvedilol was 57.3. The metabolism of the study pharmaceuticals in the shrimp was investigated. Diazepam was found to be metabolized by G. pulex and a metabolite was detected and tentatively identified as nordiazepam. For the other five study compounds no metabolites were observed and it was inferred that metabolism in G. pulex may not influence the BCF. The influence of dietary uptake was explored in the test organisms with carvedilol and fluoxetine. It was found that uptake from water was the predominant route of exposure for G. pulex but the data for N. glauca was contrasting and the exposure from the food was predominant. In both organisms a combination of food and water exposure resulted in a higher uptake of the compounds. The differences in degree of uptake from water across the organisms may be due to differences in mode of respiration, behaviour and the pH of the test system. The differences in degree of uptake from food across the organisms may be due to differences in feeding strategies. The degree of uptake of pharmaceuticals within an organism was related to the hydrophobicity of the pharmaceuticals.
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Christman, Van D. "Ecology of benthic macroinvertebrates in experimental ponds." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134927/.
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Macdonald, Hannah. "Population genetics and demographic resilience in three aquatic invertebrates." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100387/.
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Freshwater environments are threatened worldwide by external stressors and biodiversity decline, with major implications for ecosystem resilience. The genetic consequences so far have been neglected, especially for freshwater invertebrates, though their abundance, diversity, ease of sampling and functional importance renders them ideal candidates for genetic appraisal. For three freshwater invertebrates (Amphinemura sulcicollis, Isoperla grammatica and Baetis rhodani) novel microsatellite markers were developed so that genetic structure, and genetic diversity could be assessed throughout upland Wales. The aim was to investigate dispersal and the genetic response to environmental stressors. Genetic diversity in these species was compared to species diversity across whole macroinvertebrate assemblages to investigate what factors might cause a correlation between these fundamental levels of biodiversity. The demographic history of each species was also investigated with the aim of assessing whether reduced genetic diversity was due to bottlenecks and more broadly, what this indicates in terms of the populations’ resilience. Species differed in their genetic structure and genetic diversity. All three species showed effective dispersal and geneflow, with each species displaying panmixa across catchments in southern and mid-Wales. However, A. sulcicollis and I. grammatica revealed genetic isolation and reduced genetic diversity at specific northern sites. Genetic and species diversity were correlated positively only in A. sulcicollis, where isolation combined with a common driver were the likely cause. There was evidence of recent bottlenecks in all three species. All these results could be explained by an underlying genetic response to post-industrial acidification: reduced genetic diversity correlated significantly with acidity for A. sulcicollis, while reduced species diversity and genetic bottleneck signatures was consistent with chronic and episodic acidification across the Welsh region. Overall, these results show how a positive correlation between species and genetic diversity can never be assumed, and illustrate how assessments of genetic health expand insights available from traditional biodiversity assessment.
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CORTEZ, FERNANDO S. "Avaliacao ecotoxicologica do farmaco triclosan para invertebrados marinhos." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9946.
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Hopson, Adrienne M. "Impacts of Anthropogenic Noise on Aquatic Invertebrates in Wetland Habitats." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent15645874111271.
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Turner, Patricia Anne. "Macroinvertebrate drift along an elevational and stream size gradient in a southern Appalachian stream." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06302009-040521/.
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Becker, Lindsey M. "Aquatic invertebrate, vegetation, and hydrology assessment of Long Meadow Lake prior to effects of hydrological manipulations /." Link to full text, 2007. http://epapers.uwsp.edu/thesis/2007/Becker.pdf.
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Nachtrieb, Julie G. Kennedy James H. "The impact of invertebrates to four aquatic macrophytes Potamogeton nodosus, P. illinoensis, Vallisneria americana and Nymphaea mexicana /." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9058.
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Sambles, Christine. "Derivation of the molecular basis of endocrine disruption in aquatic invertebrates." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54659/.
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Endocrine disrupting chemicals (EDCs) have attracted worldwide media attention due to their feminisation effects on aquatic organisms. Studies on the environmental effects of these compounds have become increasingly important due to fears of increased infertility and their influence on the dynamics of an ecological niche. The benthic invertebrate
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Williams, Kristi. "Macroinvertebrate and crayfish communities in the Meramec River drainage basin an investigation at multiple spatial scales /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4580.
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Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 27, 2007) Includes bibliographical references.
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Nachtrieb, Julie Graham. "The impact of invertebrates to four aquatic macrophytes: Potamogeton nodosus, P. illinoensis, Vallisneria americana and Nymphaea mexicana." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9058/.
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This research investigated the impact of invertebrates to four species of native aquatic macrophytes: V. americana, P. nodosus, P. illinoensis, and N. mexicana. Two treatments were utilized on each plant species, an insecticide treatment to remove most invertebrates and a non-treated control. Ten herbivore taxa were collected during the duration of the study including; Synclita, Paraponyx, Donacia, Rhopalosiphum, and Hydrellia. Macrophyte biomass differences between treatments were not measured for V. americana or N. mexicana. The biomasses of P. nodosus and P. illinoensis in non-treated areas were reduced by 40% and 63% respectively. This indicated that herbivory, once thought to be insignificant to aquatic macrophytes, can cause substantial reductions in biomass.
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Gulish, Matthew C. "SEASONAL VARIABILITY OF AQUATIC AND TERRESTRIAL INVERTEBRATES IN A FORESTED STREAM ECOSYSTEM." Kent State University Honors College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1544453804036894.
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Moyo, Sydney. "Aquatic–terrestrial trophic linkages via riverine invertebrates in a South African catchment." Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/54427.
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Rivers play a vital role in human livelihoods and are likely to undergo substantial alteration due to climate and land use changes from an increasing human population. Mitigating the pressures facing rivers in the world requires scientists and environmental managers to understand the ecological mechanisms, and ultimately the strength, of connections between ecosystems. This understanding of connections between adjacent habitats will enable environmental managers to predict the consequences of perturbing these linkages in the future. In this thesis, aquatic-terrestrial linkages in rivers were investigated using ecologically meaningful variables including abundances, biomasses, stable isotopes and fatty acids. This study is part of a larger project entitled “Connectivity through allochthony: reciprocal links between adjacent aquatic and terrestrial ecosystems in South Africa”, in which a team of researchers assessed a variety of pathways connecting riverine and estuarine systems to land within a catchment in the Eastern Cape, South Africa. I conceptualised the flow of energy within a temperate southern hemisphere river (the Kowie River) within theoretical models of energy flow such as the River Continuum Concept (RCC; presents lotic systems as being longitudinally linked with food webs in shaded headwaters being principally driven by allochthonous energy, with the addition of autochthonous food as a minor carbon source in the lower reaches) and the Riverine Productivity Model (RPM; proposes consumers derive most of their energy from local production of phytoplankton, benthic algae and aquatic plants, as well as directly from riparian zones via terrestrial leaf litter). Using the RCC as a starting point, I collected macroinvertebrates (September 2012 to May 2013) along a longitudinal gradient and grouped them into functional feeding groups (FFGs). The results revealed that gatherers and filterers dominated in the Kowie River, and together represented 50 – 83% of the invertebrate assemblages. There was a general paucity of shredders (relative abundance was ≤ 10% across all sites and seasons). The changes in relative abundances of different FFGs did not follow predictions of the RCC along the longitudinal gradient, as there were no correlations of community structure with some physical attributes (stream width, canopy cover, distance of river) that changed along the river continuum. However, FFG abundances were related to water velocity, total dissolved solids and canopy cover. Broadly, the Kowie River data showed that changes in relative abundances of FFGs along the river continuum could not be explained by changes in physical attributes alone, and may be highly influenced by the availability of food and the chemistry of the stream. Analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes was used to estimate the contributions of algal and land-based production to consumers over space (six sites) and time (November 2012 to September 2013). Carbon contributions determined by the use of mixing models (Stable Isotope Analysis in R) revealed that consumers in the headwater assimilated mainly terrestrially-derived organic matter, with consumers in the middle and lower reaches assimilating autochthonous basal resources (macrophytes and algae). The findings from this river supported aspects of the RCC (at the headwaters; terrestrial organic matter made up 41% of consumer diets), but overall the data supported the predictions of the RPM (local production made the highest contributions of 50 – 86% to all FFGs across all seasons). The carbon isotopes of consumers and their food sources changed substantially every season, indicating that samples of food sources and consumers should be analysed many times throughout the year to capture that variability and to ensure that ephemeral components of the food web are not missed. To validate the findings from the isotope data, fatty acids were used as complementary tracers to determine the contributions of algal versus terrestrial organic matter to the consumers. Fatty acid tracers for terrestrial (Ʃω3/Ʃω6; 18:2ω6; 18:3ω3) vs aquatic (Ʃω3/Ʃω6; 20:5ω3) sources corroborated the findings from the isotope data set, as the mean ratio of Ʃω3/Ʃω6 in consumers was less than one at the headwaters (indicating allochthony), while middle and lower reaches were associated with Ʃω3/Ʃω6 > 1 (indicating autochthony). In addition to the tracer and FFG analyses for examining trophic connections between land and river, the bidirectional exchange of organisms between the riparian zone and the river was assessed using floating pyramidal traps (to measure emergence) and pan traps (for infalling invertebrates) placed at different sites in the river and the biomass in each trap was determined. The exchanges were variable over space and time, with emergence peaking in summer (169 to 1402 mg m-2 day-1) and declining in winter (3 to 28 mg m-2 day-1). Similarly, infalling invertebrates increased in summer (413 to 679 mg m-2 day-1) and declined in winter (11 to 220 mg m-2 day-1). Biomass measurements are indications of quantity that ignore nutritional quality, so I determined the bidirectional flow of invertebrates using absolute concentrations of physiologically important biochemical compounds (essential and polyunsaturated fatty acids). The fluxes of emergent and infalling arthropods peaked in summer (emergence = 0.3 to 18 mg m-2 day-1 and terrestrial infall = 0.3 to 3 mg m-2 day-1) and declined in winter (emergence = 0.01 to 0.51 mg m-2 day-1 and terrestrial infall = 0.01 to 0.03 mg m-2 day-1). However, during some seasons, no significant differences in polyunsaturated fatty acid flux in either direction were observed; this finding indicated the balance of reciprocal subsidisation via reciprocal flows of animals. Factors such as air temperature and algal productivity affected the reciprocal flows between adjacent habitats, with algal productivity being positively related to emergence while air temperature was positively correlated to infalling terrestrial invertebrates. This research enhances the growing body of literature on the function of riverine systems and offers some invaluable information on the flow of energy and the role played by invertebrates in translocating nutrients from terrestrial systems to aquatic systems and vice versa. This study unifies the concepts of the RCC and RPM and shows that these concepts are not limited only to large rivers, but are applicable to small southern temperate rivers too. However, some tenets of the theoretical models were challenged. For example, it challenges the proposition by the RCC that the fine particulate organic matter leaked from upstream breakdown of coarse particulate organic matter is predominantly allochthonous. Additionally, this study showed that in the headwaters, the RPM underestimated the role of autochthony. Overall, the results showed that the Kowie River and its riparian area are intrinsically connected. Once we understand the mechanisms controlling connections and subsidies across ecotones, we can then start to predict the consequences of disruptions to these connections by climate change and/or land use changes. To make predictions about future perturbations to rivers and riparian zones, studies like this, which considers the form and magnitude of subsidies, are needed to provide baseline information. Algal resources (e.g. epiphyton), macrophytes, riparian plants, terrestrial organisms and aquatic organisms all contributed to aquatic and terrestrial linkages in the Kowie River; therefore, it is important to conserve the different components of these ecosystems.
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Pestana, João Luís Teixeira. "Predation risk versus pesticide exposure: effects of fear and loathing on aquatic invertebrates." Doctoral thesis, Universidade de Aveiro, 2007. http://hdl.handle.net/10773/955.
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Doutoramento em BiologiaOs organismos aquáticos apresentam respostas plásticas à presença de predadores que são induzidas por pistas químicas presentes na água. Estas respostas além de minimizar os efeitos de predação, têm também custos associados que podem incluir alterações na tolerância às variações ambientais tais como contaminação por pesticidas. Os efeitos dos pesticidas em sistemas naturais resultam assim da toxicidade mas também do efeito nas interacções predador-presa. Apesar de extremamente relevante nomeadamente para análises de risco, as possíveis interacções entre contaminação por pesticidas e pressão predatória, não estão ainda esclarecidas nem tão pouco os mecanismos comportamentais e fisiológicos que as medeiam. O principal objectivo da investigação aqui apresentada foi assim avaliar o efeito de um insecticida, imidacloprid, em diferentes espécies de invertebrados aquáticos sujeitos a diferentes níveis de risco de predação. Numa primeira fase o efeito do Imidacloprid nas comunidades naturais foi avaliado com base em estudos de mesocosmos conjuntamente com ensaios ecotoxicológicos baseados em respostas individuais. Pulsos de concentrações relevantes de imidacloprid revelaram-se extremamente tóxicas para insectos aquáticos. A alimentação e metabolismo de uma espécie de plecóptero, Pteronarcys comsctocki, mostraram-se como respostas sub-letais sensíveis e assim ferramentas válidas em termos de biomonitorização dos efeitos do pesticida. Usando um clone de Daphnia magna foi também avaliada a relativa importância das substâncias de alarme e de kairomonas de truta (Salmo trutta) como mediadores de respostas anti predação em Daphnia. A combinação de kairomonas e substâncias de alarme mostrou ser necessária para uma resposta mais forte induzindo alterações no comportamento, fisiologia e história de vida de Daphnia. Esta combinação de sinais químicos pode ser assim usada para avaliar efeitos de intimidação ou de risco de predação. Utilizando metodologias ecotoxicológicas padronizadas avaliaram-se em laboratório as respostas de D. magna, Chironomus riparius e Sericostoma vittatum, expostos a concentrações sub-letais de Imidacloprid bem como diferentes níveis de risco de predação. Observaram-se efeitos significativos de concentrações relevantes de Imidacloprid na fisiologia e comportamento dos insectos enquanto que D. magna se mostrou muito mais tolerante respondendo apenas a concentrações bastante altas de imidacloprid. A exposição combinada a ambos os stressores foi avaliada considerando mecanismos de acção ecotoxicológicos dos dois stressores e usando diferentes abordagens nomeadamente modelos de referência para misturas químicas e análises de variância. No caso dos insectos, foram observados efeitos aditivos na maioria dos parâmetros testados sendo que a exposição a concentrações sub-letais de Imidacloprid inibiu algumas das respostas anti predatórias com potenciais efeitos em termos de mortalidade devido a predação em campo. Para D. magna a exposição simultânea aos dois stressores mostrou desvios relativamente aos modelos de referência que incluem sinergismo para algumas dos parâmetros testados. Os resultados obtidos mostram que invertebrados sujeitos a elevada pressão predatória são mais afectados por concentrações sub-letais de pesticidas. Dado que muitas espécies de invertebrados são simultaneamente sujeitas ao risco de predação e à contaminação por pesticidas, o estudo do efeitos combinados destes dois factores nas comunidades aquáticas, é extremamente importante para melhor prever e interpretar os efeitos ecológicos da contaminação por pesticidas em sistemas naturais.
Aquatic species rely on plastic traits to defend themselves against predators. The induction of these antipredator defences is mediated by water-borne chemical cues. These induced defences have associated costs which can include decreased tolerance to future environmental change such as pesticide contamination. The effects of pesticides in natural systems can be a result not only of their direct toxicity but also of their indirect effects on predator-prey interactions. Despite their relevance for risk assessment, the interactive effects of pesticide contamination and predation stress are poorly understood because the underlying behavioural and physiological mechanisms are largely unstudied. The main objective of this thesis was therefore to assess the toxic effects of imidacloprid, a widely-used insecticide, on different invertebrate species under different levels of predation risk. First, the effects of Imidacloprid on freshwater communities were assessed using field-deployed mesocosms and organism level bioassays. Pulses of environmentally-relevant concentrations of imidacloprid were highly toxic to non-target aquatic insects. Feeding and metabolic responses of a stonefly species Pteronarcys comsctocki, proved to be a good early warning indicator of pesticide detrimental effects. Using a clone of Daphnia magna, the relative importance of alarm cues and fish kairomones (Salmo trutta) were studied as initiators of Daphnia antipredator defences. Although behavioural responses could be triggered by single cues, a combination of alarm cues and predator-specific compounds induced stronger responses and were necessary to induce complete antipredator responses (behavioural, physiological and in the life-history) of daphnids. A combination of both types of chemical cues could thus be used as surrogate for the effects of intimidation posed by predators. Using standardized laboratory toxicological methodologies different responses of D. magna, Chironomus riparius and Sericostoma vittatum d to sublethal concentrations of imidacloprid were assessed under different levels of predation risk. Significant effects of environmentally-relevant concentrations of imidacloprid were observed on insect behaviour and physiology. Higher concentrations of imidacloprid were necessary to elicit effects on D. magna, relative to the other species tested. Considering the ecotoxicological mode of action of imidacloprid and perceived predation risk, the effects of simultaneous exposure to both stressors were assessed using different approaches with additive reference models and analysis of variance. Both stressors acted additively for most responses tested in the different insect species with exposure to sublethal concentrations of imidacloprid also inhibiting antipredator responses with potential negative consequences in terms of mortality from predation in the field. For D. magna, exposure to both stressors showed significant deviations from the reference models results including synergism for same endpoints tested. The results obtained provide insight into the conditions under which interactions between these stressors are likely to occur: invertebrates such as daphnids, midges and caddisflies living under fish predation stress will be more affected by sub-lethal concentrations of Imidacloprid than populations at low predatory pressure. Since predation risk and pesticides can be considered 'similarly-acting' stressors in an ecological sense, studying both types of stress within the same mechanistic framework can be of great value providing compatible data for modelling and allowing improved interpretation of ecological effects of relevant stressors.
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Cappo, Michael. "Frogs as predators of organisms of aquatic origin in the Magela Creek system, Northern Territory /." Title page, contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09SM/09smc249.pdf.
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Blakely, Tanya Jillaine. "Tree holes as habitat for aquatic and terrestrial invertebrates in mixed broadleaf-podocarp rainforest, New Zealand." Thesis, University of Canterbury. Biological Sciences, 2008. http://hdl.handle.net/10092/1698.
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Little is known about the spatial distribution and abundance of tree holes in New Zealand’s native forests, or the invertebrate communities that they support. I found that tree holes were common on five endemic tree species, belonging to the families Fagaceae and Podocarpaceae in the mixed broadleaf-podocarp rainforest of Orikaka Ecological Area, Buller District, New Zealand. However, tree holes were not uniformly distributed throughout the forest, with more holes found on the three podocarp species, Prumnopitys ferruginea, P. taxifolia and Dacrycarpus dacrydioides, than on Nothofagus fusca or N. menziesii. Nevertheless, Nothofagus fusca had the largest holes of any of the tree species sampled and larger trees generally had larger holes. Large, hole-bearing Nothofagus fusca trees support a specialist hole-dwelling vertebrate fauna in New Zealand and worldwide, tree holes provide habitat for a range of invertebrate species. Using specially-designed emergence traps, I collected invertebrates emerging from naturally-occurring dry tree holes and compared this assemblage with invertebrates inhabiting leaf litter on the forest floor and those dispersing aerially throughout the study area. At the higher taxonomic resolution (i.e., Order or Class), community composition within the tree holes was highly variable, and there was no strong distinction between invertebrates from tree holes, leaf litter or Malaise traps. Moreover, although some beetle species emerging from tree holes were found exclusively in tree holes, most of these were represented by a single individual. Consequently, only minor differences in species composition were detected between beetle assemblages from tree holes, leaf-litter and those aerially dispersing throughout the forest. In contrast, the aquatic invertebrate assemblage within water-filled tree holes was highly distinctive from that in ground-based freshwater ecosystems, with only six aquatic taxa in common between all freshwater habitats. Using experimental water-filled tree-hole microcosms, I found that species richness and community composition within these microcosms were primarily driven by resource concentration, although habitat quality (i.e., water chemistry parameters) was also an important determinant of the identity and composition of colonising species. Overall, my study has shown that tree holes are common in the study area, and are likely to be more abundant in New Zealand’s indigenous forests than previously thought. Moreover, these generally small, discrete forest ecosystems support a diverse array of terrestrial invertebrates as well as a distinctive aquatic invertebrate community that is primarily structured by organic matter resource availability. These findings not only represent an important advance in our knowledge of New Zealand’s freshwater invertebrate biodiversity, but also highlight the need for further investigation into these unique forest canopy habitats which may well be at risk from deforestation and land use change.
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Ono, Erika Ramos. "Efeito da retirada da mata ripária sobre a estrutura dos grupos funcionais de alimentação em assembleias de macroinvertebrados bentônicos." Botucatu, 2018. http://hdl.handle.net/11449/153196.
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Orientador: Virginia Sanches UiedaResumo: Macroinvertebrados bentônicos são comumente utilizados como bioindicadores da qualidade do habitat em riachos. Estes estudos podem ser realizados através de uma abordagem taxonômica ou funcional da comunidade. Na abordagem funcional, a classificação em grupos funcionais de alimentação (FFG - Functional Feeding Groups) baseia-se nos mecanismos de apreensão do alimento e nos recursos consumidos. O estudo teve o objetivo de verificar o efeito de alterações na mata ripária sobre a estrutura dos FFG em comunidades de macroinvertebrados bentônicos. Estudamos 36 riachos, separados em três tipos de entorno: com mata ripária nas duas margens (florestado), com mata em uma das margens e pastagem na outra (intermediário) e sem mata nas duas margens (pastagem). A análise das variáveis ambientais indicou uma diferenciação dos riachos florestados e da maioria dos intermediários devido a maiores valores de material alóctone e oxigênio dissolvido e menores de vegetação nas margens e substrato fino, quando comparados aos de pastagem. A análise da abundância da fauna em cada FFG indicou uma diferença entre entornos somente para coletores, com valores significativamente menores nos florestados quando comparados aos de pastagem e intermediários. Já a análise aplicada aos dados de presença-ausência mostrou diferença entre entornos somente para os predadores, indicando diferença significativa na composição entre riachos florestados e de pastagem. A análise da diferenciação dos entornos considerando... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Benthic macroinvertebrates are commonly used as bioindicators of the habitat quality in streams. These studies may be carried out through analyzes with taxonomic or functional approach of the assemblage. In the functional approach, the classification of macroinvertebrates into Functional Feeding Groups (FFG) is based on the mechanisms of food´s apprehension and the resources consumed. This study aimed to verify the effect of the changes in riparian forest upon the structure of FFG in assemblages of benthic macroinvertebrates. We studied 36 streams, separated in three types of land use: with riparian forest on both banks (forest), with forest on one of the banks and pasture on another (intermediate) and without forest on both banks (pasture). The analysis of environmental variables showed a differentiation of the forest and most of the intermediate streams due to high values of allochthonous material and dissolved oxygen and low amounts of vegetation on the banks and unconsolidated substrate, when compared to pasture streams. The analysis of the abundance of the fauna in each FFG indicated a difference between types of land use only for gathering collectors, with significantly low abundance in forested streams when compared to pasture and intermediate ones. On the other hand, analysis applied to the presence-absence data showed distinction between land uses only for predators, indicating significant difference in the composition of forest and pasture streams. The analysis of t... (Complete abstract click electronic access below)
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Contardo, Jara Valeska. "Physiological biomarkers in moderate sensitive aquatic invertebrates for water quality assessment in urban watercourses." Berlin dissertation.de, 2008. http://d-nb.info/990963586/04.
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Benier, Jean-Michel. "The role of farm dams as refugia for aquatic invertebrates in a salinised landscape, south Western Australia." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2004. https://ro.ecu.edu.au/theses/828.
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In a salinised landscape farm dams may represent the last truly freshwater surface resource, and therefore provide refuge habitats for the biota of wetlands affected by increasing salinity. One wetland threatened by increased salinity in south-west Western Australia is Lake Toolibin. It is listed as a Wetland of International Importance under the Ramsar Convention in recognition of its high conservation value, and remediation actions to halt (and possibly reverse) further increases in salinity are being undertaken at this wetland. Farm dams act as aquatic refugia if they convey resistance and/or resilience to the biotic communities of a disturbed habitat. This study proposed to investigate farm dams as potential refuge habitats from which aquatic macroinvertebrate species could recolonise Lake Toolibin. To do this the physico-chemistry and aquatic macroinvertebrate community of fourteen farm dams surrounding Lake Toolibin, and Lake Walbyring an adjacent wetland that has remained comparatively fresh, were sampled in autumn and spring 1998. Comparison was made to previous studies of Lake Toolibin and Lake Walbyring to detennine if aquatic macroinvcrtebrate species from these wetlands were found in the broader landscape. Results indicate that the aquatic macroinvertebrate communities of Lake Toolibin and Lake Walbyring have been altered by increasing salinity. Both the physico-chemical and aquatic macroinvertebrate data collected from farm dams indicate a high degree of heterogeneity between sites, which is considered to be typical of that throughout the wheatbelt region of Western Australia. Of the 80 aquatic macroinvertebrate taxa previously recorded at Lake Toolibin, 41 were recorded in the surrounding farm dams and 30 from Lake Walbyring, in spring 1998. Of the 38 taxa recorded at Lake Walbyring in spring, 16 were either not collected or were rare in surrounding farm dams at the corresponding time. The aquatic macroinvertebrate community composition of farm dams was dominated by species of Coleoptera, Hemiptera, Chironomidae and Ostracoda. All species recorded from farm dams and Lake Walbyring in 1998 were considered to be freshwater species tolerant of a wide range of salinities, and widely distributed throughout south-west Western Australia. It was concluded that, when considered as a mosaic of habitat types and not as isolated systems, farm dams are important refuge habitats for the aquatic macroinvertebrate species of Lake Toolibin. The farm dams will provide a mechanism for the maintenance of aquatic invertebrate species richness and abundance. Refuge farm dam habitats can therefore contribute to the conservation and management of wetland biodiversity in a salinized landscape such as the Western Australian wheatbelt.
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Palmer, Shiree. "The ecological role of a common seastar (Patiriella spp.) within intertidal cobble fields : a thesis submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Marine Biology /." ResearchArchive@Victoria e-Thesis, 2010. http://hdl.handle.net/10063/1240.
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Mitchell, Richard Morgan Feminella Jack W. "The influence of coarse woody debris, disturbance, and restortion on biological communities in sandy coastal plain streams." Auburn, Ala., 2009. http://hdl.handle.net/10415/2022.
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Arundel, Helen Patricia, and lswan@deakin edu au. "Invertebrate larval dynamics in seasonally closed estuaries." Deakin University. School of Ecology and Environment, 2003. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20061011.142951.
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Estuarine benthic assemblages are often numerically dominated by polychaetes. The limits of these populations are determined by larval, and probably to a lesser extent adult movement. A previous study (Newton 1996), indicated that planktonic polychaete larvae were very abundant over the summer months in the Hopkins River; however, the identification and source of these larvae was not known. Defining the extent of a population, and therefore the likelihood of that population recovering following a perturbation, is crucial for effective estuarine management.
This study investigated both the likely source of the larvae, (i.e. estuarine or marine) and the extent of larval dispersal within and between estuaries by addressing the following questions: Which taxa produced the planktonic larvae? Are these taxa resident estuarine species? Are the larvae of different taxa evenly distributed within the estuary or do physicochemical parameters or other factors influence their abundance? Are the same larvae found in other estuaries along the coast? and Is there exchange of these larval taxa with the marine environment and other estuaries?
Larvae were identified and described by culturing commonly occurring planktonic larvae until adult characteristics appeared. The spionids, Carazziella victoriensis and Prionospio Tatura, numerically dominated the plankton in the Hopkins and the spionid, Orthoprionospio cirriformia was recorded from the Hopkins, Curdies and Gellibrand estuaries. Two spionids, Carazziella sp. and Polydora sp. were identified from tidal waters.
Mouth status and physicochemical conditions (salinity, temperature and dissolved oxygen) were monitored in each estuary. Whereas the Merri and Gellibrand estuaries were predominantly stratified over the sampling period, the Curdies was more often well mixed and the Hopkins varied from well mixed to stratified. The duration of mouth opening and hence the opportunity for larval exchange also varied in each estuary. The Merri River was closed for 13.5% of days over the study period, the Gellibrand River for 18.4%, the Hopkins River for 49% and the Curdies River for 71.0%.
The distributions of larvae at spatial scales of metres, 100s of metres and kilometres were investigated within a single estuary. While the same larvae, C. victoriensis, P. Tatura and bivalve larvae, were found along the length of the Hopkins estuary the abundances varied at different spatial scales suggesting different processes were influencing the distribution of P. Tatura larvae, and C. victoriensis and bivalve larvae.
The distribution of larvae between several estuaries was investigated by monitoring meroplankton at two sites at the mouth of each of the four estuaries approximately monthly (except for winter months). Different meroplanktonic assemblages were found to distinguish each estuary. Further, C. victoriensis and P. Tatura larvae were only recorded in the Hopkins but larvae of the spionid, Orthoprionopio cirriformia were detected in the Hopkins, Curdies and Gellibrand estuaries.
The extent of larval exchange with other estuaries and the marine environment was determined by monitoring tidal waters. Settlement trays were also deployed to determine if larvae were moving into estuaries and settling but not recruiting. P.
tatura larvae were not detected in the tidal waters of any estuary and while C. victoriensis and O. cirriformia were found in both flood and ebb tides there was no evidence of movement of theses taxa to other estuaries. Larvae of the spionids, Carazziella sp. and Polydora sp., were found in tidal waters of each estuary but were rarely detected in the plankton within the estuaries. Neither species was found as an adult in background cores from any estuary, nor with the exception of a few individuals in the Merri, were they detected in settlement trays in any estuary.
I conclude that the source of the larvae of C. victoriensis, P. Tatura and O. cirriformia is estuarine and while C. victoriensis, and O. cirriformia move in and outh of the source estuary in tidal waters there was no evidence for movement to other estuaries. The spionids, Carazziella sp. and Polydora sp were considered to be marine and
while they moved in and out of estuaries in tidal waters they did not usually settle in the estuaries.
The results of this study are a crucial first step in the development of ecological models to better understand dispersal in seasonally closed estuaries that are typical of southern Australia. This study emphasises the unique physicochemical characteristics and biological assemblages within these estuaries and the need for estuarine management to reflect these differences.
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Harms, Nathan Earl. "Comparison of Heteranthera Dubia (Jacq.) MacM.-associated Macroinvertebrates Between Georgraphical Regions in the United States." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28427/.
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Macroinvertebrates associated with the aquatic plant, water stargrass (Heteranthera dubia), were sampled from 12 waterbodies in four regions of the United States from June to August 2005. Taxa richness, evenness, and diversity were lowest in the Lower Midwest (LMW) region, and higher in Northern sites, especially the Upper Midwest (UMW), and Northeast (NE). While relative abundance varied from site to site and region to region, utilization of the plant by functional groups remained fairly constant. Collector-gatherers consistently comprised the largest portion of invertebrates sampled. The shredder/ herbivore functional group comprised an average of 17 % of total groups. Through an exhaustive literature review, it was found that shredder/ herbivores of water stargrass have not been reported in the literature. Because of this, the herbivore group was analyzed separately and consisted of 2,383 specimens representing 23 species. The most common groups were Rhopalosiphum sp., Nectopsyche spp. and chironomids. No differences were found in herbivore diversity or evenness between sampling regions, but species richness was significantly different.
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Wale, Matthew A. "The effects of anthropogenic noise playbacks on marine invertebrates." Thesis, Edinburgh Napier University, 2018. http://researchrepository.napier.ac.uk/Output/1255476.
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Anthropogenic sound has profoundly changed the acoustic environment of aquatic habitats, with growing evidence that even a short exposure to man-made sound sources can negatively affect marine organisms. Marine invertebrates have received little attention regarding their responses to anthropogenic sound, despite their pivotal role in marine ecosystems, and preliminary evidence of their sensitivity. In this thesis, I critically review the methods used in studies investigating the effects of anthropogenic noise on marine invertebrates. I identify methodological trends that have developed along the timeline of this topic, and use this information to suggest three research strategies to further the development of research in this field. From this review, current knowledge gaps are identified, and two main routes to address them are taken in this thesis. Firstly, to address the shortage of particle motion data in anthropogenic sound literature, two new low-cost and easily accessible particle motion sensors were developed and tested, one of them at 0.1% of the cost of currently commercially available models. These sensors will allow the measurement and reproduction of the sound fields experienced by marine invertebrates in bioacoustic research, even when research budgets are tight. Particle motion is the main sound component detected by invertebrates, yet neglected in many aquatic bioacoustical studies. Secondly, to expand on the comparably small quantity of research investigating the effects of anthropogenic sound on marine invertebrates, a series of controlled laboratory experiments were conducted. Two commercially and ecologically important model species were chosen, the blue mussel Mytilus edulis, representing sessile benthic invertebrates, and the European lobster Homarus gammarus, representing mobile benthic invertebrates. Experiments on M. edulis were conducted taking a mechanistic, integrative approach to investigate the effects of sound on multiple levels of biological organisation, including biochemistry, physiology, and behaviour. The ultimate aim was to understand the underlying drivers behind, and interactions between, responses. Comet assay analysis of haemocytes and gill cells demonstrated a significant six-fold higher single strand breakage in the DNA of cells of mussels exposed to ship-noise playback, compared to those kept under ambient conditions. Superoxide dismutase analysis did not identify an excess of superoxide ions, and glutathione, and glutathione peroxidase assays showed no increase in either glutathione or glutathione peroxidase. TBAR assays however revealed 68% more thiobarbituric acid reactive substances, indicating lipid peroxidation in the gill epithelia of noise exposed specimens. Algal clearance rates and oxygen-consumption rates of noise-exposed mussels were significantly lower (84% reduction and 12% reduction respectively), than those of control animals, while valve gape was significantly (60%) wider. This seemingly converse reaction indicates a shock response in mussels with the onset of noise exposure. Finally, at the genetic level, heat shock protein 70 expression was investigated, but no change was identified during noise exposure. Investigation into the noise induced behavioural responses of H. gammarus suggests seasonal differences in behaviour, using movement as a metric, in response to anthropogenic noise playbacks. During both summer and winter exposures, lobsters spent most time away from the highest noise area (98% of the observed time in summer and 78% in winter). The observed seasonal differences in the time spent in the highest noise area (2% in summer and 22% in winter) could be linked to the lobsters' requirement for shelter during winter. This requirement seems to have had a stronger influence over the animals' behaviour than any desire to avoid high noise levels. The information generated in this thesis can be used by researchers working in the field of marine sound to develop well rounded studies exploring the effects of sound on not only marine invertebrates but other faunal groups as well. The construction details provided to produce low cost particle motion sensors, will allow bioacoustic researchers to easily include particle motion measurements in all future studies investigating the effects of sound on fish and invertebrates. The results of the conducted mussel and lobster experiments evidence how multiple aspects of invertebrate biology can be affected by noise. The observed impacts on both sessile and mobile life forms highlight that the effects of noise cannot be fully understood before a wide range of species with different biological and ecological traits have been studied. The integrative approach to noise research used here can serve as a model for other species, and the results pooled to inform governments and industry of the effects of anthropogenic noise in the marine environment.
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Atienzar, Franck Andre. "Development of the random amplified polymorphic DNA (RAPD) technique to measure the effects of genotoxinsin aquatic organisms." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/1757.
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Studies were undertaken to evaluate the potential of random amplified polymorphic DNA (RAPD) to detect DNA effects (including DNA damage and mutations) in aquatic invertebrates, following their exposure to a variety of environmental contaminants under laboratory conditions. After rigorous optimisation of the RAPD method, the protocol, which used a high annealing temperature (50"C for 10-mer primers), was found to generate good-quality DNA profiles from groups of organisms belonging to the bacterial, plant and animal kingdoms. The RAPD method was initially used to detect benzo(a)pyrene [B(a)P] and copper-induced DNA effects in the water flea Daphnia magna and ultraviolet-mediated DNA effects in the marine alga Palmaria palmata. The results clearly showed that changes occurred in RAPD profiles obtained from the exposed populations when compared to controls. In these studies, the effect of the genotoxins at higher levels of biological organisation (e.g. Darwinian parameters and/or fitness parameters) were also investigated and were compared with genomic DNA template stability (GTS), a qualitative index representing clear changes in panems compared to control RAPD profiles. The results from these experiments revealed that GTS could be more sensitive than growth parameters and showed at least equal or even greater sensitivity than other measures of fitness. Changes in RAPD profiles were believed to be the result of DNA effects, namely adduct formation, DNA breakage, oxidative damage and mutations and possibly other effects (e.g. variation in gene expression). Nevertheless, the nature and amount of DNA effects could only be speculated because diverse events may induce the same category of changes (i.e. variation in band intensity, appearance of bands, and disappearance of amplicons) in RAPD patterns. Further studies confirmed that RAPD had the potential to qualitatively detect oestrogen and xeno-oestrogen -induced DNA effects in barnacles. Additional experiments emphasised that oxygen radicals and variation in gene expression may induce significant changes in RAPD profiles. To further understand the effects of DNA lesions and mutations on RAPD patterns, individual types of DNA damage were created in vitro. The results clearly indicated that BaP DNA adducts, DNA photoproducts. and DNA breakages had significant effects on RAPD profiles but that diverse types of DNA damage may induce the same category of changes in RAPD patterns which render the interpretation of the results difficult. It was also concluded that mutations could be detected provided they do not arise in a random fashion. Finally, an attempt was made to determine the kinetics of DNA damage and DNA repair and whether changes in patterns obtained from B(a)P exposed Daphnia magna could be transmitted to successive generations. This strategy was developed to distinguish between mutations and DNA damage. The results showed that some bands obtained from the exposed populations were transmitted to the first and/or second generation but not to the third. It was concluded that the transmission of modified genetic material to the offspring was more likely to be the result of large genomic rearrangements and/or base methylation (epigenetic processes) rather than point mutations. In conclusion, the results presented in this research project show the potential of the RAPD assay as a useful method for the qualitative assessment of DNA effects including genotoxicity and changes in gene expression. The main advantage of this technique is that it can be applied to any species without requiring any information about the nucleotide sequence. In the field of ecogenotoxicology, its main advantage lies in its sensitivity and speed to detect a wide range of DNA damage including DNA breakage, DNA adducts, oxidative damage as well as mutations (including point mutations and large rearrangements). On the other hand, RAPD only allows a qualitative assessment of the DNA effects and the nature of the changes occurring in profiles can only be speculated. Finally, a great deal of further experimentation and validation are required in order to assess the applicability of the technique to a variety of other species and pollutants, particularly under field conditions.
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McLenaghan, Natalie Ann. "Benthic macroinvertebrate diversity in a shallow estuary : controls on nutrient and algal dynamics /." Online version of thesis, 2009. http://hdl.handle.net/1850/9704.
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Scholl, Eric. "The influence of water velocity on aquatic macroinvertebrate functional structure and production in the Cache River in Southern Illinois." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1158.
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The Cache River, located in southern Illinois, faces a unique set of restoration challenges due to multiple anthropogenic modifications to the watershed. In 1915 the Cache River was disconnected and divided into two sub-watersheds, the upper Cache River (UCR) and the lower Cache River (LCR). This alteration has led to impairments in both sections of the Cache River. The UCR currently suffers from channel incision and wetland loss due to an increase in channel slope, while the LCR experiences decreased flows and related habitat degradation. Currently, watershed managers are proposing to restore a more natural flow regime to the LCR through some degree of hydrologic reconnection. I quantified the effects of small-scale differences in flow velocities on snag-dwelling aquatic macroinvertebrates in the UCR and LCR. My study was designed to provide critical information on potential ecological responses to proposed reconnection of the Cache River by examining the effects of flow on elements of ecosystem structure (macroinvertebrate community structure, diversity, richness, evenness, biomass, and abundance) and function (secondary production). Total snag-dwelling macroinvertebrate abundance was higher in the LCR (p < 0.001), and both total biomass and total production did not differ between the UCR and LCR. Passive filter-feeders (families Hydropsychidae and Simuliidae), EPT taxa (orders Ephmeroptera Plecoptera and Trichoptera), and Elmidae were more abundant and had higher biomass on snags in the UCR compared to the LCR. Due to high variability in estimates, only Elmidae production was higher in the UCR (p < 0.05), with non-significant trends of higher production of passive filter-feeders and EPT taxa in the UCR. Non metric multidimensional scaling (NMDS) ordinations showed different communities on snags in the UCR and LCR, and analysis of similarity indicated these differences were significant (ANOSIM Global R = 0.98, p < 0.05). This UCR community was more diverse (p < 0.05) and composed of larger-sized individuals than the LCR (p < 0.001). In contrast, the LCR community was composed mainly of taxa that are associated with very low flows (e.g., zooplankton), tolerant of degraded conditions (e.g., Isopoda and Chironomidae), and generally smaller in body size. Although not statistically significant, there was a trend for higher total production in the LCR (28.90 ± 54.51) (mean ± 95% CI) than the UCR (10.22 ± 6.43). This trend was driven primarily by a patchily distributed Chironomidae, which were highly productive on some LCR snags. However, given the degraded water quality in the LCR, the ultimate fate of this production is not clear. The more natural flow regime in the UCR is likely driving many of the differences between the UCR and LCR that I observed, but relationships may be complex, as flow influences biota in numerous direct and indirect ways. This study is the first I know of to examine the structure and function of macroinvertebrate communities prior to hydrologic restoration of a river. Results will assist resource managers in the justification, planning, and execution of hydrologic restoration in the Cache watershed. Given that many river restoration projects are not based on sound ecological information and principles, this project can also serve as a model for future river restoration efforts.
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Leonard, Norman. "The effects of the invasive exotic Chinese tallow tree (Triadica sebifera) on amphibians and aquatic invertebrates." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/656.
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This dissertation addresses the question of how leaf litter from trees affects animals that live in aquatic environments, with an emphasis on the effect of Chinese tallow (Triadica sebifera) leaf litter on anuran larvae (i.e., frog tadpoles). This question is important to our understanding of how allochthonous inputs to aquatic habitats drive biodiversity in wetlands. It also addresses a timely conservation concern in southeastern Louisiana where invasion by Chinese tallow trees (Triadica sebifera) is displacing native trees. The invasion process is homogenizing forest composition and changing the quantity and quality of litter inputs to ponds from those produced by a mixture of native species to that of a single invasive species. This change in litter quality may have important effects on aquatic animals because leaf litter that falls into ponds is an important source of nutrients and energy in wetland foodwebs. Leaf litter also affects water quality via effects on dissolved oxygen and leaching of defensive compounds, which may subsequently affect the diversity and performance of aquatic animals. Herein I address these issues by presenting a series of studies in which tadpole and aquatic invertebrate responses were tested using leaf litter from Chinese tallow leaves and three native tree species. The major findings of this research are: (1) Leaf litter has a direct effect on water quality (2) Chinese tallow can cause differential survival and performance of tadpoles (3) Differences in water quality due to leaf litter can cause changes in tadpole behavior (4) Chinese tallow leaf litter breaks down much faster than litter from native trees (5) Difference in litter breakdown rates influence aquatic community composition.
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DeHaan, Maureen. "The possible effects of peat mining on aquatic invertebrates in the Lake Muir Wetlands, Western Australia." Thesis, DeHaan, Maureen (1986) The possible effects of peat mining on aquatic invertebrates in the Lake Muir Wetlands, Western Australia. Honours thesis, Murdoch University, 1986. https://researchrepository.murdoch.edu.au/id/eprint/40888/.
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Small scale dry peat mining operations can have a significant environmental impact on peatland ecosystems. At present, peat mining operations are proposed for the Lake Muir Wetlands. These wetlands are part of a nature reserve which contains six new species of aquatic water mites. This study investigated the present aquatic invertebrate community structure in the Lake Muir Wetlands, and reviewed the relevant literature to determine the possible effects of peat mining on those invertebrates.
Three fen peatlands near Manjimup (Poorginup, Tordit-Gurrup and Byenup) were sampled in December 1985 and April 1986 to determine their water chemistry, and all three wetlands were found to be freshwater (0.1 - 7.0%0), circumneutral (pH 5-8) and meso-eutrophic. A total of 103 species of aquatic invertebrates were recorded with only eight species being common between the three wetlands. Indices of similarity demonstrated a definite dissimilarity between the three wetlands based on species richness. The class lnsecta dominate the invertebrate fauna, accounting for 72% of the total number of species recorded.
Species abundance/m3 showed a variation with season, and was lower in comparison to urban wetlands studied in Western Australia. Species diversity and evenness were also compared, with the Lake Muir Wetlands having a higher species diversity, but similar evenness.
Based on the literature reviewed there are numerous environmental impacts associated with the various stages of peat mining. The stages identified as most detrimental to aquatic invertebrates are the clearing and draining of the peatland. The potential effects of these two aspects of the mining operation on invertebrates are both direct and indirect. The potential adverse impacts of these disturbances on the Lake Muir aquatic invertebrates are proposed and possible causal mechanisms discussed.
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Jatar, Muriel M. "Assessing the Effect of Selenium on the Life-cycle of Two Aquatic Invertebrates: 'Ceriodaphnia dubia' and 'Chironomus dilutus'." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24036.
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Runoff and effluent discharge from mining activities has resulted in elevated concentrations of selenium in aquatic ecosystems. Bioavailability is dependent on chemical speciation. Although dissolved inorganic Se species are not directly toxic to organisms, uptake by primary producers and subsequent biotransformation to organo-selenium species substantially increase risk and bioaccumulation potential, potentially impairing reproduction in high-order organisms. The effects of dietary selenium exposure were assessed in two aquatic invertebrates: Ceriodaphnia dubia and Chironomus dilutus. Two generations of these organisms were exposed to seleniferous algae grown in 0-40 μg L-1 selenate. Dissolved selenate was readily absorbed and concentrated by algal species Pseudokirchneriella subcapitata and Chlorella kesslerii. Se had no effect on survival at treated concentrations. Dietary selenium exposures had little effect on reproductive endpoints in either invertebrate species, suggesting that invertebrates have the ability to regulate chronic Se exposures from dietary sources. These results provide valuable information concerning the effects of dietary selenium in aquatic invertebrates.
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Henkanaththegedara, Sujan Maduranga. "Ecological Complexity of Non-Native Species Impacts in Desert Aquatic Systems." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26697.
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Without an adequate understanding of complex interactions between native and non-native species, management of invasive species can result in unforeseen detrimental impacts. I used both field and laboratory experiments to study reciprocal species interactions between the endangered Mohave tui chub (Siphateles bicolor mohavensis) and invasive western mosquitofish (Gambusia affinis). I also examined the impacts of both fish species on the aquatic invertebrate communities in desert springs. I demonstrate a case of intraguild predation (IGP) as a mechanism facilitating co-persistence of the endangered Mohave tui chub with invasive mosquitofish using field mesocosm experiments. In this case of IGP, adult tui chub prey on adult and juvenile mosquitofish, while adult mosquitofish prey on tui chub eggs and/or larvae. I conducted laboratory predation trials to assess if IGP was size-structured due to predator gape-limitation. I explored sex specific differences in gape-size limitation in mosquitofish, because mosquitofish are sexually dimorphic. Larval tui chubs had lower survival in the presence of female mosquitofish than in the presence of males. Reciprocally, male mosquitofish had lower survival than the females in the presence of Mohave tui chub. These results combined with vulnerability modeling supported that IGP in this system is size structured based on gape-size limitation. These results collectively suggest size-structured IGP may facilitate the co-persistence of these two fish species. My findings also suggest that mosquitofish may not be a limiting factor for the persistence of the endangered Mohave tui chub. Further, habitats currently harboring mosquitofish were considered as future refuge habitats for Mohave tui chub, a management option previously un-available. In addition to such reciprocal interactions between fish species, recently established fish populations may impact unique invertebrate communities. Mesocosm experiments with sympatric and allopatric populations of tui chub and mosquitofish showed negative impacts of both fish species on changes of invertebrate community structure. Specifically, fish caused population declines and, in some cases, extirpations of various invertebrate taxa. These results suggest important conservation implications of invasive fish as well as protected fish transplants into fishless desert springs. Overall my research emphasizes the complexity of ecological interactions between native and non-native fish species in desert aquatic systems.
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Burdon, Francis John. "The effects of stream productivity on aquatic-terrestrial linkages." Thesis, University of Canterbury. Biological Sciences, 2004. http://hdl.handle.net/10092/1415.
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The potential relationship between riparian arachnids and aquatic insect productivity was assessed in forest streams throughout the central South Island of New Zealand. Initially, a survey was conducted of thirty seven, first-third order forest streams. Streams were selected to represent a range of benthic invertebrate standing crops (as a surrogate measure of "productivity") from Banks Peninsula streams with relatively high benthic invertebrate densities to acid mine drainage streams near Reefton that were almost devoid of aquatic life. At each site benthic invertebrate densities and biomass were measured in riffle habitats and adjacent gravel bars were sampled for terrestrial invertebrates. At a sub-set of 16 sites, a 20 metre longitudinal web-building spider survey was conducted along each bank of the stream. As an additional component, a 20 metre transect starting at the stream margin and running perpendicularly into the forest was used to survey the density of web-building spiders with increasing distance from the stream. Results from the survey of in-situ stream insect biomass and gravel bar invertebrates showed a strong relationship between aquatic insect biomass and the biomass of riparian arachnids (R2 = 0.42, P < 0.001) having accounted for potentially confounding factors such as stream size, elevation, substrate and disturbance. The 20 metre longitudinal survey showed that streams with the highest in-situ insect biomass had significantly higher densities of web-building spiders along their banks (R2 = 0.28, P < 0.05), having accounted for potential confounding variables of elevation, habitat architecture and stream and channel width. The stream to forest survey showed a strong exponential decay in web-building spider densities with increasing distance from the stream (R2 = 0.96, P < 0.0001). Regardless of stream productivity web-building spiders were most abundant at the stream margins and rapidly declined to very low densities 20 metres from the stream. In order to further test the relationship between riparian web-building spider densities and stream insect productivity, a stream fertilization experiment was conducted on six first-second order streams in the Maimai experimental catchment, Reefton. Three streams were enriched by the addition of a fertiliser solution mainly consisting of sodium nitrate for seven months, and the other three streams were used as controls. Water chemistry, benthic invertebrate communities, emerging aquatic adults, and the densities of web-building spiders along the stream corridor and in the forest were monitored in three seasons (spring, summer and autumn) over the course of the nutrient-addition. By the end of the experiment, conductivity was significantly higher in nutrient-addition streams than in the control streams (F = 80.5, P < 0.001), but chlorophyll concentrations showed no significant differences between treatments. Both benthic mayfly densities (F = 6.15, P < 0.05) and the biomass of adult aquatic dipterans (Chironomidae, Simuliidae) (F = 9.25, P < 0.01) were significantly higher in nutrient-addition streams in the last sampling round. Spiders recorded from intercept traps indicated that by the end of the experiment spider activity was significantly higher within 2.5 metres of the nutrient-addition streams (F = 5.70, P < 0.01). However, seasonal densities of web-building spiders along the stream margin and in the forest decreased with no significant differences observed between nutrient-addition and control streams. The results from these studies indicate that adult insects emerging from streams represent an important source of prey that could influence the biomass and abundance of riparian arachnids. Additionally, the results imply that stream productivity and size could mediate the strength of the interaction between riparian and stream habitats. Moreover, feedback mechanisms present in both systems could have implications for such interactions. The elevated densities of web-building spiders observed at the stream margin led to the proposal of the "Highway Robber" hypothesis. This hypothesis suggests that such higher densities of spiders are the result of increased insect activity along the stream corridor: the emergence of adult aquatic insects was predicted to vary less over temporal and spatial scales than that of terrestrial insects due to the poorly synchronized life histories in many New Zealand stream insects. I conclude by suggesting that there are numerous anthropocentric perturbations such as loss of heterogeneity, introduced species, pollution and habitat degradation that could undermine and decouple the intimate linkages between aquatic and terrestrial ecosystems.
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Johnson, Philip C. (Philip Charles). "Impacts of the Pyrethroid Insecticide Cyfluthrin on Aquatic Invertibrate Populations in Outdoor Experimental Tanks." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc279350/.
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The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were generally higher in microcosms, while aqueous half-life was shorter in the smaller systems.
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Dudley, Melissa B. Chambliss C. Kevin. "Accumulation of trifluralin and trinitrotoluene (TNT) in two aquatic invertebrates formation and persistence of unextractable biotransformation products /." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5155.
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Agatz, Annika. "Consequences of short-term feeding inhibition from exposure to pesticides for individuals and populations of aquatic invertebrates." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/5538/.
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Recently, several scientific committees of the European Commission have identified research needs to enhance the risk assessment of plant protection products (PPPs). This PhD explicitly focuses on contributing to the research needs of assessing effects under highly time-variable exposure, increasing the ecological realism in effect assessment approaches, considering effect assessment of combined stressors (natural and anthropogenic) and improving ecological modelling. The presented work focuses on the observation of potential impacts of PPPs (imidacloprid and carbaryl) on feeding of aquatic invertebrates (Gammarus pulex and Daphnia magna) under more environmentally-realistic exposures. Isolated feeding depression and its combination with additional stress is explored. Investigations include the determination of consequences of alterations in feeding for further behavioural traits of individuals and its transposition to the population level. An ecological model is used as a virtual laboratory to allow the interpretation of complex impacts observed which in turn helps to evaluate the model used. A key finding is that feeding assays with G. pulex are able to reveal impacts of PPPs at environmentally-relevant concentrations and that the measurement of recovery potential is important. However, the method used requires further improvement in order to extrapolate impacts to the population and ecosystem level. The possibility of short-term impacts on feeding causing severe impacts at the individual and population level is shown for D. magna. Direct extrapolation from the feeding assay with imidacloprid to other individual traits is not possible. Impacts are found to depend on food availability and the individual’s reproductive strategy, which is found to be more flexible under multiple stresses than has been reported in the literature. Further research is required in order to generalise these findings.
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Birnbaum, Jenny Sue. "Associations of watershed and instream environmental factors with aquatic macrofauna in tributaries of the Pedernales River, Texas." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/2411.
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Intermittent headwater streams serve important functions in semi-arid rangelands, both for humans and wildlife. However, few studies have assessed species-environment relationships for fish and benthic macroinvertebrate assemblages in these systems. Additionally, no published studies could be found that addressed the influence of juniper coverage in watersheds on assemblage structure of these taxa. Increased juniper coverage in recent decades is believed to be associated with decreased water yields in central Texas streams. During summer 2003 and spring 2004, I examined potential effects of juniper cover on aquatic ecology. Fishes, benthic macroinvertebrates, and the physicochemical habitat were investigated in spring-fed headwater tributaries of the Pedernales River. My objectives were to: 1) describe the typical fish and benthic macroinvertebrate assemblages in headwater creeks of the Pedernales River basin; 2) compare seasonal variability of fish and benthic macroinvertebrate assemblages; 3) identify species-environment relationships in this river basin; and 4) evaluate the influence of juniper coverage in the watershed, relative tolocal and landscape-level environmental factors, on the structure of fish and benthic macroinvertebrate assemblages. A total of 4,181 individual fish were collected in summer 2003 samples, 551 fish were collected in spring 2004, 59,555 macroinvertebrates were captured in summer 2003 samples, and 51,500 macroinvertebrates were collected in spring 2004. Assemblages were typical for the area and habitat conditions. Faunal richness was lower in spring than in summer, possibly due to a combination of sampling after a relatively dry period in the spring, and lack of winter refugia in the form of deep pools. Fish assemblages may structure based principally on abiotic factors in spring, the harsher season (less available water), whereas predation pressure may influence structure in summer. Another important environmental gradient for both fish and invertebrate assemblages contrasts pool and run mesohabitats. In general, juniper cover was weakly associated with fish and invertebrate assemblages, although it tended to be associated with relatively high quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). In these intermittent streams, local-scale environmental factors probably are the dominant influences on fish and benthic macroinvertebrate assemblages. Implications for future studies are discussed.
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Santos, Liliana Raquel Assunção. "Avaliação de risco ambiental de pesticidas para ecossistemas aquáticos - representatividade das espécies padrão de invertebrados." Master's thesis, ISA/UTL, 2012. http://hdl.handle.net/10400.5/5331.
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Mestrado em Engenharia do Ambiente - Gestão Ambiental - Instituto Superior de AgronomiaWith the main aim of verifying whether Daphnia magna is sufficient for the evaluation of the environmental risk of pesticides to aquatic ecosystems, toxicity values of 218 insecticides were analyzed. For each one the relative tolerance (Trel) value was calculated to compare the sensitivity of species from different taxonomic groups with that of D. magna. The taxonomic groups were grouped in arthropods, non-arthropod invertebrates, fish, algae/macrophytes and based on Trel values the species sensitivity distribution (SSD) were defined. For the arthropods the influence of the mode of action (MOA) on vulnerability to the insecticide was also analyzed. Still in the arthropods group, for each species, the class, order and family they belong to were identified. To check the necessity of inclusion of a second species studies of relationship were performed, between D. magna, Americamysis bahia and Chironomus riparius. As far as the SSD curves are concerned, for the different groups the most sensitive one was the arthropods group in both values of EC50 and NOEC. Taking into consideration MOA the group of neonicotinoids was the most sensitive one in EC50 case and the GABA – gated chloride channel antagonists in NOEC. The most sensitive taxonomical group was Mysida and it was the combination of Daphnia plus A. Bahia that generated the greater percentage of protection.
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Whelly, Mark P. "Aquatic invertebrates in wetlands of the oil sands region of northeast Alberta, Canada, with emphasis on Chironomidae (Diptera)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0015/MQ52675.pdf.
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Seitz, Frank [Verfasser], Mirco [Akademischer Betreuer] Bundschuh, and Ralf [Akademischer Betreuer] Schulz. "Factors triggering the ecotoxicity of metal-based nanoparticles towards aquatic invertebrates / Frank Seitz. Betreuer: Mirco Bundschuh ; Ralf Schulz." Landau : Universität Koblenz-Landau, Campus Landau, 2015. http://d-nb.info/1107775604/34.
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PUSCEDDU, FABIO H. "Avaliacao ecotoxicologica do farmaco triclosan para invertebrados de agua doce com enfase em ensaios com sedimento marcado ('SPIKED SEDIMENT')." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9498.
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Made available in DSpace on 2014-10-09T12:27:20Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:34Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Drinkard, Maureen Katherine. "IMPACTS OF A FLOOD PULSING HYDROLOGY ON PLANTS AND INVERTEBRATES IN RIPARIAN WETLANDS." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1342805313.
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Amaning, Kwarteng. "Streamwater and sediment chemistry of Ohio's Western Allegheny Plateau ecoregion and their relation to aquatic life." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1153757100.
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Lüderwald, Simon [Verfasser], Mirco [Akademischer Betreuer] Bundschuh, Mirco [Gutachter] Bundschuh, and Ralf [Gutachter] Schulz. "Environmental processes transforming inorganic nanoparticles: implications on aquatic invertebrates / Simon Lüderwald ; Gutachter: Mirco Bundschuh, Ralf Schulz ; Betreuer: Mirco Bundschuh." Landau : Universität Koblenz-Landau, Campus Landau, 2020. http://d-nb.info/120442733X/34.
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Moles, Sánchez Juan. "Antarctic heterobranch molluscs: diving into their challenging ecology, taxonomy, and systematics." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/399046.
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This thesis covers three important aspects of Antarctic heterobranchs: ecology, taxonomy, and systematics. The first section deals with ecological interactions of several nudibranchs. In Chapter 1, we chemically characterize a new natural product (a homosesterterpene) called granuloside, from Charcotia granulosa Vayssière, 1906; remarkably, this is the first record of this type of compound in marine organisms. In Chapter 2, we assess the origin, function, and distribution of granuloside in this nudibranch; we found glandular structures probably responsible for storing granuloside, as a defensive mechanism against predators, like the sympatric starfish, Odontaster validus Koehler, 1906. We also hypothesize that granuloside is de novo biosynthesized by C. granulosa. This chapter reflects how organisms from polar latitudes have similar defensive strategies to those of temperate and tropical zones. In Chapter 3, a new species of ectosymbiont copepod, Anthessius antarcticus n. sp., living on C. granulosa is described. This is the first record of such association in Antarctica and the first time that this copepod genus has been found living on a nudibranch. In Chapter 4, we study the development of two anthobranchs, Doris kerguelenensis (Bergh, 1884) and Bathydoris hodgsoni Eliot, 1907, both with intracapsular development; we provide new data on the egg masses characteristics, and embryos morphology and anatomy, throughout their development; we also studied at which ontogenetic stage their natural products appear. We concluded that both nudibranchs exhibit developmental periods of up to several years; their embryos are physically defended by a thick egg capsule, while juveniles already rely on de novo biosynthesized defensive compounds. In the second section of this thesis, our interdisciplinary taxonomic and systematic studies, including histology, tomography, electron microscopy, and molecular tools, allowed us to describe three new species of heterobranchs. In Chapter 5, we provide integrative taxonomic evidence for the establishment of a new family (Newnesiidae), and the description of a new species of Cephalaspidea (Newnesia joani n. sp.) with eurybathic and circumpolar distribution; this discovery traces the origin of the cephalaspideans (distributed worldwide) to Antarctica. In Chapter 6, we performed a three-dimensional (3D) anatomical reconstruction and compared the two nudibranchs Doto antarctica and the new species Doto carinova n. sp.; their phylogeny reveals intriguing questions concerning the development of the reproductive system in this genus; 3D reconstructions reveal also the presence of probable giant neurons associated with the nervous system, which were unknown in this genus so far. Finally, in Chapter 7 we provide new evidence of bipolar geographic distributions by describing a new species of nudibranch, Doridunculus punkus n. sp., using only non-destructive tomographic techniques. Our results highlight both the need and the relevance of multidisciplinary approaches to study biodiversity and ecological interactions in heterobranch molluscs from a poorly studied area of the planet, such as Antarctica.Esta tesis doctoral abarca tres aspectos relevantes de los heterobranquios antárticos: su ecología, taxonomía y sistemática. La primera sección trata sobre interacciones ecológicas en varios nudibranquios. En el capítulo 1, caracterizamos químicamente un nuevo producto natural (un homosesterterpeno) denominado granuloside, de Charcotia granulosa Vayssière, 1906; cabe destacar que ésta es la primera vez que se halla este tipo de compuestos en organismos marinos. En el capítulo 2, evaluamos el origen, función y distribución del granuloside en dicho nudibranquio; hallamos estructuras glandulares probablemente encargadas de acumular granuloside como mecanismo defensivo frente a depredadores, como la estrella de mar Odontaster validus Koehler, 1906. Además, sugerimos que C. granulosa biosintetiza granuloside de novo. Este capítulo refleja cómo los organismos de latitudes polares poseen estrategias defensivas similares a los de las zonas templadas y tropicales. En el capítulo 3, se describe una nueva especie de copépodo, Anthessius antarcticus n. sp., ectosimbionte de C. granulosa; este es el primer registro de este tipo de asociaciones en la Antártida y la primera vez que se describe este género viviendo en un nudibranquio. En el capítulo 4, estudiamos el desarrollo de dos antobranquios, Doris kerguelenensis (Bergh, 1884) y Bathydoris hodgsoni Eliot, 1907, con desarrollo intracapsular; aportamos nuevos datos morfológicos y anatómicos sobre las puestas, huevos y embriones a lo largo de su desarrollo; también estudiamos el estadio ontogenético en el que aparecen sus productos naturales; concluimos que ambas especies tienen periodos de desarrollo de varios años, sus embriones se defienden físicamente gracias a la gruesa cápsula del huevo, mientras que los juveniles ya sintetizan sus propios compuestos defensivos. En la segunda sección de la tesis, nuestros estudios taxonómicos y sistemáticos interdisciplinares, incluyendo técnicas de histología, tomografía, microscopía electrónica y moleculares, han permitido la descripción de tres especies nuevas de heterobranquios. En el capítulo 5, se aporta evidencia taxonómica para establecer una nueva familia (Newnesiidae), y la descripción de una nueva especie de Cephalaspidea (Newnesia joani n. sp.) con distribución euribática y circumpolar; este descubrimiento traza el origen de los cefalaspideos (distribuidos en todo el mundo) hasta la Antártida. En el capítulo 6, realizamos una reconstrucción anatómica tridimensional (3D) y comparamos los dos nudibranquios Doto antarctica y la nueva especie Doto carinova n. sp.; su filogenia revela interesantes cuestiones relativas a la evolución del sistema reproductivo en este género; además, las reconstrucciones 3D revelan la existencia de posibles neuronas gigantes asociadas al sistema nervioso, hasta ahora desconocidas en este género. Por último, en el capítulo 7, proporcionamos nuevas pruebas de una distribución geográfica bipolar, mediante la descripción de una nueva especie de nudibranquio, Doridunculus punkus n. sp., usando exclusivamente técnicas tomográficas no destructivas. Nuestros resultados ponen de manifiesto la necesidad y la relevancia de utilizar enfoques multidisciplinares para el estudio de la biodiversidad y las interacciones ecológicas en moluscos heterobranquios, en especial en un continente todavía poco estudiado, como es la Antártida.
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Bergamino, Roman Leandro. "Spatial and temporal variations in trophic connectivity within an estuarine environment : benthic-pelagic and terrestrial-aquatic linkages via invertebrates and fishes." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017799.
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Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
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Leiva, Martinez Carlos. "Population genomics, phylogeographic history, and evolutionary patterns in Antartic shallow-water benthic invertebrates." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668297.
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Benthic organisms inhabiting the shallow waters of the Southern Ocean are considered excellent models to study evolutionary processes, population connectivity patterns, and adaptation. They have evolved in an extreme environment, with expanding and retreating periods following glacial cycles, in an alternation pattern. Repeated rounds of population fragmentation in glacial refugia during glacial cycles followed by expansions and secondary contacts during interglacials were the main evolutionary force that brought Antarctic shallow-water ecosystems to their current state. In my PhD dissertation I have investigated in detail these singular evolutionary histories left in the genomes of our target species. Besides the past geological events, currently, threats from global warming arrive to the isolated southernmost continent. Indeed, coastal waters off West Antarctica are some of the most affected oceanic regions of the planet by global warming, with rather pessimistic projections for the near future. Considering this and the increasing local threats to which shallow-water ecosystems are exposed, it is fundamental to develop a well-connected network of Marine Protected Areas (MPAs) throughout the Southern Ocean. Despite genetic connectivity is not usually considered in MPA planning, population genetic studies can provide extremely valuable information to design connected MPA networks. In my dissertation I have also disentangled gene-flow patterns of Antarctic shallow-water benthic invertebrates, aiming to help to improve the current status of Southern Ocean MPAs.
In order to achieve my goals, I combined information coming from ‘traditional’ genetic markers, single nucleotide polymorphisms (SNPs) derived from restriction-site associated DNA sequencing (ddRADseq), transcriptomes, and draft-level genomes. A wide range of species presenting different reproductive modes was selected in order to test whether this factor plays a role on connectivity and evolutionary patterns in the explained scenario of glacial alternations: the brooding congeneric nemerteans Antarctonemertes valida, A. riesgoae, and A. unilineata; the demosponges Dendrilla antarctica and Mycale acerata, which present lecithotrophic larvae; and the annelids Pterocirrus giribeti (new species described in the Chapter 1 of my PhD dissertation) and Neanthes kerguelensis, that presumably presents planktotrophic larvae.
Our results regarding the evolutionary history of our target species revealed different glacial-refugium strategies independent of their reproductive mode, and generalised signals of bottleneck events. Moreover, blurred species boundaries were detected for the Antarctonemertes lineages, with a central role of glacial cycles in their introgressive evolutionary history. Additionally, we identified adaptive genes for particular glacial-refugium strategies and for the rise of prezygotic barriers during speciation and reinforcement events. Our connectivity results confirmed that genetic connectivity in the Southern Ocean is not determined by a priori dispersal abilities resulting from different reproductive strategies. We revealed an overall high gene flow along the Western Antarctic Peninsula (WAP), which is particularly exceptional for sponges and brooding species. Interestingly, loci under divergent selection were identified for D. antarctica despite admixture, broadly differentiating between the populations of Northern and Southern WAP. We suggest that ongoing natural selection is governed by differences in sea-ice extent and duration, exhibiting the vulnerability of the WAP benthic ecosystems due to the decline in the sea ice predicted for the near future. Finally, we demonstrated that long-distance connectivity did not surpass the regional WAP scale, supporting the implementation of an MPA covering the WAP and the coastal waters off the South Orkneys.
Overall, the studies presented in my PhD dissertation represent a step forward in understanding global forces and processes affecting the evolutionary history of Antarctic marine organisms. We illustrated the adaptability of shallow-water benthic invertebrates to the natural changes of the Southern Ocean, while manifesting their vulnerability to future global warming. Remarkably, we highlight the importance of using population genetic data of various benthic invertebrate species to implement MPA networks in one of the most threatened areas of the planet by global warming. The results of my thesis will be fundamental to address the suitability and effectiveness of an MPA network comprising the already implemented MPA at South Georgia and South Sandwich Islands and the proposed MPA covering the WAP and the South Orkney Islands, essential for the survival of Antarctic marine ecosystems.
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Gray, Duncan Peter. "Ecological connectivity in braided riverscapes." Thesis, University of Canterbury. School of Biological Sciences, 2010. http://hdl.handle.net/10092/4181.
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Rivers are hierarchical networks that integrate both large and small scale processes within catchments. They are highly influenced by variation in flow and are characterised by strong longitudinal movement of materials. I conducted an extensive literature review that indicated braided rivers lie at the upper end of the river complexity gradient due to the addition of strong lateral and vertical connectivity with their floodplains. The management of these rivers requires an understanding of the connective linkages that drive complexity, however in developed regions few braided river systems remain intact. The large number of relatively pristine braided rivers in New Zealand provided a unique opportunity to study physical and biotic patterns in these large dynamic systems. Initially I examined horizontal connectivity through patterns in regional and local diversity in eleven braided rivers in the North and South islands of New Zealand. Subsequently, the next component of my thesis focused on vertical connectivity through intensive investigations of energy pathways and the recipient spring stream food-webs.
The eleven river survey included sampling of multiple reaches and habitats (main channels, side braids, spring sources, spring streams and ponds) and confirmed the importance of lateral habitats to invertebrate diversity. However, I found that large spatial scales made a greater contribution to diversity than small scales, such that major differences occurred between rivers rather than habitats. This result suggested either a role for catchment-scale factors, such as flow, or biogeographic patterning. Subsequent analysis of the relationships between invertebrate diversity and the physical environment indicated strong regulation by flow variability, but also biogeographic community patterns. Braided rivers are clearly disturbance dominated ecosystems, however the effects of disturbance are manifest in different ways across the riverscape.
The role of vertical hydrological connectivity in linking the different components of the floodplain was investigated by tracing carbon pathways from the terrestrial floodplain to spring-fed streams and their communities. Using δ13C isotope signatures it was possible to show that inorganic carbon in groundwater was derived from terrestrial vegetation and subsequently incorporated into spring stream food-webs. However, the degree to which a stream community uses groundwater as opposed to allochthonous carbon is affected by the successional stage of riparian vegetation, a function of the shifting habitat mosaic that is regulated primarily by flow variation and sediment dynamics. In summary, the structure of braided river ecosystems is regulated primarily at the catchment scale, but connectivity at smaller scales plays an important role in determining ecological structure and function.
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Chandler, Houston Cawthorn. "The Effects of Climate Change and Long-term Fire Suppression on Ephemeral Pond Communities in the Southeastern United States." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51190.
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In the southeastern United States, ephemeral wetlands in pine flatwoods provide important habitat for amphibians and aquatic invertebrates, but extensive deforestation has destroyed or isolated many wetlands and fire suppression has altered vegetation in others. My goals were to identify how wetland hydroperiods have changed through time and to examine the effects of long-term fire suppression on aquatic communities, including Reticulated Flatwoods Salamanders (Ambystoma bishopi) and Ornate Chorus Frogs (Pseudacris ornata). Chapter 1 used a modeling approach to relate wetland hydroperiods to current climate conditions and to hindcast historic conditions. Over the past 118 years, hydroperiods were often unfavorable for A. bishopi reproduction, and in recent years hydroperiods were shortened by persistent drought. Chapters 2 and 3 focused on identifying the effects of shifting from an open, grass dominated wetland to a wetland with high canopy cover and little herbaceous vegetation. In Chapter 2, I quantified amphibian and invertebrate communities in several wetlands. A. bishopi and P. ornata tended to occupy wetlands with lower canopy cover and higher herbaceous vegetation cover. Aquatic invertebrate abundance was generally higher in wetlands with lower shrub density and lower canopy cover. In Chapter 3, I examined how a reduction in herbaceous vegetation affected tadpoles when a predatory crayfish was present using two experiments. Crayfish were effective predators of both species across all vegetation treatments and often caused nonlethal tail injury. My results suggest that managers should focus on ensuring that wetland basins regularly burn, and wetlands with longer hydroperiods should be a management priority.Master of Science