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1
Voparil, Ian M. "Lipid Solubilization by Marine Benthic Invertebrates." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/VoparilIM2003.pdf.
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Nisbet, Katherine. "Exploring connectivity of marine benthic invertebrates." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569247.
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With the marine environment subjected to ever increasing anthropogenic pressures resulting in biodiversity and habitat losses, there is an urgent need to implement effective management and conservation strategies to limit these losses. One such strategy is the designation of Marine Protected Area (MPA) networks, with the central concept that individual MPAs are connected to its neighbours within the network However, determining scales of connectivity in an environment that varies considerably both spatially and temporally is inherently difficult. Larval dispersal is a main driver of population connectivity, and planktonic larval duration (PLD) is frequently used to infer dispersal distance. Thus far studies have predominantly focused on fish and tropical species, using approaches such as larval dispersal modelling, otolith microchemistry or genetic estimates of connectivity. This thesis aimed to assess the levels of connectivity in a range of benthic invertebrates characteristic of offshore shelf seas of the Northeast Atlantic, at a range of spatial and temporal scales. This was achieved by: (1) examining the variation in PLDs of a typical benthic assemblage, then using this information to examine the variation in realised dispersal at multiple locations using particle tracking software; (2) assessing habitat preferences for the same species, and exploring how the distribution of broad habitats would affect connectivity of species; and (3) using microsatellite markers to determine the genetic structure of the exploited scallop Pecten maximus at both a localised scale (Isle of Man) and a regional scale covering over half its range. While biological variation, in the form of PLD, did affect dispersal potential of common benthic invertebrates, it was the physical factors of hydrographic regime and substrate type within a species given dispersal range that played the most important role in determining ultimate dispersal distance and location. Additionally, the scale of genetic structure of the scallop Pecten maximus, with Norway genetically distinct from Scotland, Ireland and Isle of Man but weaker or no structure within those regions, highlighted the interaction of biological and physical factors. Ultimately, this thesis has provided valuable insight into the drivers of connectivity in the marine benthos, but further work, particularly more collaborative studies across multiple fields, is required if MPAs are to achieve their aims in the face of a changing environment.
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Chouinard, Julie. "Metal concentrations in benthic invertebrates in peatlands." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6549.
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In order to assess the influence of various abiotic and biotic factors on metal accumulation in peatlands, insects were collected from bogs, mineral poor fens and circumneutral fens located in Central Ontario. The peatlands represented a gradient in alkalinity from 0 (acid bogs) to 200 $\mu$eq$\cdot$L$\sp{-1}$ (circumneutral fens). Further, the peatlands had important hydrological differences with no obvious inflows in the bogs and inflow/outflow streams in the fens. Given these contrasting environments, it was hypothesized that there would also be differences in metal accumulation in the associated biota. The results of this study indicate that the acidification of peatlands, whether natural or anthropogenic, will not lead to greater availability of metals such as Zn, Cu, Al, and Mn. High organic matter levels may serve to mitigate the effects of acidification on metal availability in such peatlands. (Abstract shortened by UMI.)
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Haas, Elske Maria de. "Persistence of benthic invertebrates in polluted sediments." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/75485.
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Orav-Kotta, Helen. "Habitat choice and feeding activity of benthic suspension feeders and mesograzers in the northern Baltic Sea /." Tartu, Estonia : Tartu University Press, 2004. http://dspace.utlib.ee/dspace/bitstream/10062/489/5/Kotta.pdf.
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Chan, King-tung. "Multivariate analysis of benthic macroinvertebrate communities of Hong Kong streams /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18037045.
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Boyd, Sheree. "Benthic invertebrate assemblages and sediment characteristics." Click here to access this resource online, 2009. http://hdl.handle.net/10292/727.
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Cold seep ecosystems in the deep sea are fuelled by chemosynthetic processes based on methane emission to the sediment surface from gas hydrate disassociation, methanogenesis or thermogenic processes. While cold seep ecosystems have been studied in the last three decades worldwide, little is known about New Zealand’s cold seep habitats and associated fauna. A joint German-New Zealand cruise to the Hikurangi Margin in early 2007 enabled biological and sediment sampling to investigate the biological and sedimentological relationships and variability of seeps and their faunal diversity. Multi-disciplinary approaches were employed that included Xray radiography, stratigraphic descriptions, lebensspuren traces analysis, sediment grain size analysis, determination of total organic content, carbonate content and its stable isotopic composition, and analysis of benthic invertebrate assemblages of seep habitats. The results of this study revealed three distinctive habitats and associated fauna based on the sediment characteristics and faunal type. Habitat 1 includes all sites pertaining to Omakere Ridge, a seep-related habitat comprised of layers of very poorly sorted, sandy silt, shell hash and bands of methane-derived authigenic aragonitic carbonate nodules with low total organic content (TOC). Due to the characteristics of the sediments and death assemblages of molluscs, it is inferred that Habitat 1 methane seepage is actively diffusive, waning or dormant. Habitat 2 describes sites that are either non-seep or relic and applies to those at Bear’s Paw and Kaka. Habitat 2 constituted of shell hash overlain with very poorly sandy silt, and low carbonates content and low to medium TOC. Habitat 3 describes non-seep related habitats, and includes all sites of the Wairarapa region and one reference site from Kaka also falls into this category. Sediments for Habitat 3 constituted poorly sorted silt with high TOC and low carbonate content which can be explained by their close proximity to land and converging sea currents. The mineral components of the background siliciclastic sediments for all sites studied originated in the Tertiary mudstone of the East Coast Basin. The characteristics of seep habitats of the Hikurangi Margin were comparable to that of the Northern Hemisphere modern seep counterparts, although the abundance and distributions of seep fauna were low. Results from this research have enhanced our understanding on the spatial and variability of methane fluxes and their affects on the duration of cold seep ecosystems, especially for New Zealand. However, more such studies are essential to increase our understanding of seep sediments and explain disturbance-sediment-benthic invertebrate interactions.
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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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Hooper, Garnet James. "Effects of algal structure on associated motile epifaunal communities." Thesis, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268881.
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BUSCHI, EMANUELA. "Diversity of microbiomes associated with benthic invertebrates inhabiting Antarctic ecosystems." Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274555.
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Il numero sempre più alto di studi condotti sui microbiomi ha evidenziato l’importanza che queste associazioni rivestono nello sviluppo, nella salute e nella fitness degli organismi con cui i microbiomi vivono associati. In ambienti estremi come l’Antartide, i microbiomi sembrano avere un’importanza cruciale nel creare interazioni fondamentali per l’adattamento dei loro ospiti. Gli obiettivi di questa tesi sono: i) studiare la biodiversità dei microbiomi associati a diversi invertebrati marini antartici, ii) esplorarne l’origine, confrontando i microbiomi associati agli organismi con le comunità batteriche che abitano nei sedimenti circostanti, e iii) verificare se i fattori ambientali svolgano un ruolo attivo nel modellare la loro composizione tassonomica. I risultati hanno mostrato che, nonostante i microbiomi associati ai policheti antartici (Leitoscoloplos geminus, Aphelocaeta palmeri, Aglaophamus trissophyllus) possano variare in modo significativo tra gli individui, è possibile individuare dei core, sia a livello intraspecifico sia interspecifico, che contribuiscono significativamente all'intera comunità batterica associata. I taxa batterici associati ai policheti sono completamente diversi da quelli presenti nei sedimenti circostanti, suggerendo una potenziale trasmissione verticale o diverse capacità adattative dei microbiomi ai due diversi “habitat”. Molteplici fattori (i.e., non solo fattori ambientali ma anche quelli biologici come lo stato fisiologico e le abitudini di alimentazione) influenzano, a diversi gradi, la composizione tassonomica dei microbiomi associati ai policheti antartici. Nella stella marina antartica Odontaster validus la posizione geografica è il principale fattore che spiega le differenze trovate nella composizione tassonomica dei microbiomi, sebbene siano state riscontrate alcune somiglianze tra individui raccolti in luoghi diversi, suggerendo la presenza di altri fattori in grado di selezionare comunità batteriche simili. La presenza esclusiva di batteri specifici associati a stelle marine che vivono in determinate aree suggerisce una potenziale trasmissione orizzontale dei microbiomi, probabilmente acquisiti attraverso diverse abitudini alimentari che le stelle marine hanno sviluppato nelle suddette aree. Questa tesi di dottorato fornisce nuove informazioni sui microbiomi antartici, evidenziando una forte variabilità della loro composizione e complessità delle relazioni con gli ospiti esaminati, potenzialmente dovute, oltre ai fattori ambientali, anche alle caratteristiche biologiche degli ospiti.Growing studies on host-associated microbiomes are highlighting the important role of microbes in the development, health and fitness of their hosts. This might be particularly true in remote and extreme environments, such as the Antarctic ecosystem, where the host and its microbiome could evolve together establishing peculiar and close interactions. This study aims: i) to investigate the biodiversity of microbiomes of different Antarctic invertebrates, ii) to explore the potential sources of the host-associated microorganisms by comparing them with microbial communities inhabiting the surrounding sediments, and iii) to verify the role of environmental setting in shaping their taxonomic composition. Results revealed that microbiomes of Antarctic polychaetes (Leitoscoloplos geminus, Aphelocaeta palmeri, Aglaophamus trissophyllus) showing significant variability among individuals, but that both intra-specific and inter-specific core microbiomes contribute for a significant fraction to the whole microbial assemblage. Bacteria associated with polychaetes were completely different from those in the surrounding sediments, suggesting a potential vertical transmission or the presence of different adaptative/selective conditions of the two “habitats”. Multiple factors (i.e., not only environmental factors but also biological ones such as physiological state and feeding habits) can influence to different extent the taxonomic composition of microbiomes associated with Antarctic polychaetes. In the Antarctic sea star Odontaster validus, the geographic location was identified as the main factor influencing the taxonomic composition of microbiomes, but this was not a general rule. In fact, high similarities were found among microbiomes of individuals collected in different locations, suggesting the presence of other drivers able to select similar microbial communities. The presence of exclusive bacterial families in sea-star microbiomes suggests a potential horizontal transmission of bacterial taxa, probably acquired through different feeding habits that the sea star might have developed in the different basins. This PhD thesis provided new information on Antarctic microbiomes, highlighting a strong variability of their composition and complexity of the relationships with the investigated hosts, potentially due to, besides environmental settings, also to hosts’ biological features.
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Andrade, Maria Helena da Silva. "O fenômeno da \"decoada\" no Pantanal do rio Paraguai, Corumbá/MS: alterações dos parâmetros limnológicos e efeitos sobre os macroinvertebrados bentônicos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-19092011-142519/.
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Este trabalho teve como objetivo investigar a hipótese de que a decoada (alteração dos parâmetros físicos e químicos da água) é um fenômeno natural importante na estruturação da comunidade de invertebrados bentônicos do Pantanal do rio Paraguai, bem como a caracterizar a comunidade de macroinvertebrados bentônicos quanto à composição, abundância de organismos e riqueza em função das alterações ambientais provocadas pela decoada. Além disso, pretendeu-se contribuir para o conhecimento da biota do pantanal de Mato Grosso do Sul com o intuito de subsidiar ações de prevenção e/ou mitigação de possíveis impactos ambientais. Os ambientes escolhidos foram dois corpos de água adjacentes ao rio Paraguai, sendo um com características lênticas (Baía Tuiuiú) e outro, semi-lóticas (Bracinho), Corumbá/MS, ambos sob o efeito do pulso de inundação. O capítulo um realizou uma caracterização limnológica dos dois corpos de água ao longo de um ciclo hidrológico, enfatizando as alterações provocadas pela decoada, por ocasião da subida das águas. O capítulo 2 objetivou estudar a composição e a distribuição da fauna de Chironomidae relacionando-as com as alterações limnológicas ao longo de um ciclo hidrológico (abril/2008 a fevereiro/2009), enfatizando a influência da decoada. O capítulo 3 pretendeu conhecer a composição de Oligochaeta, considerando as relações com fatores abióticos, no intuito de contribuir para o entendimento do fenômeno da decoada bem como subsidiar posteriores trabalhos e ações relacionados à gestão da planície pantaneira, objetivando sua manutenção e conservação. A decoada é um evento que potencializa a desestruturação do ambiente, agindo significativamente sobre as populações de invertebrados bentônicos. O fato de não ter sido encontrado nenhum organismo vivo durante a ocorrência do fenômeno destaca a sua importância enquanto fator ecológico essencial na dinâmica das populações biológicas dos ecossistemas pantaneiros.This study aimed to investigate the hypothesis that the decoada(change in physical and chemical parameters of water) is an important natural phenomenon in the community structure of benthic invertebrates in the Pantanal of the Paraguay River, and to characterize the benthic macroinvertebrate community regarding the composition, richness and abundance of organisms as a function of environmental changes caused by the \'decoada\'. In addition, soughted to contribute to the knowledge of the biota of wetland of Mato Grosso do Sul in order to support programs to prevent and / or mitigate potential environmental impacts. The areas chosen were two bodies of water adjacent to the Paraguay River, one with lentic feature (Tuiuiú Bay) and another, semi-lotic (\'Bracinho\'), Corumbá / MS, both of them suffering the effect of pulse flood. The chapter 1 conducted a limnological characterization of the two water bodies along a hydrological cycle, emphasizing the changes caused by the \'decoada\', when the water level rises. Chapter 2 aimed to study the composition and distribution of Chironomidae fauna relating them to limnologicals changes over a hydrological cycle (the april/2008 to february/2009), emphasizing the influence of the decoada. Chapter 3 intended know the composition of Oligochaeta, considering the relationships with environmental factors in order to contribute to the understanding of the phenomenon of \'decoada\' and support further work and actions related to the management of the Pantanal, aiming to maintain the ecosystem and related services. The decoada is an event that enhances the disintegration of the environment, acting significantly on populations of benthic invertebrates. The fact that no organism had been found alive during the occurrence of the phenomenon underscores its importance as an essential ecological factor in the dynamics of biological populations of wetland ecosystems.
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Stanwell-Smith, Damon Peter. "Larval ecology of benthic marine invertebrates at Signy Island, Antarctica." Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338610.
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Murray, Fiona. "Functional contributions of benthic invertebrates to ecosystem process and functioning." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201938.
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Many of the processes on earth which are essential for sustaining life are driven by biological systems and it is functional diversity aswell as species richness which determines the health and sustainability of ecosystems. Ecosystem functions, from primary production to decomposition, are determined by the interactions both between organisms and between organisms and their environment. As such, there has long been an appeal in classifying species by their roles in ecological communities rather than by taxonomic groupings. However, there is often a disconnect between the criteria used to classify species into functional groups, often common morphological attributes, and the effect that the organisms within those groups have on specific ecosystem functions as the appropriateness of the classification criteria is rarely empirically tested. This thesis investigates inter- and intra-species variation in benthic invertebrates with respect to their effects on ecosystem processes (particle reworking and bioirrigation) and functions (nutrient cycling) and considers whether species can be grouped for single and multiple ecosystem functions in different environmental contexts. Overall the results show that species can be grouped by their effects on specific single ecosystem functions, but that these groups cannot be applied across multiple functions and processes. Further they show that species’ contributions to ecosystem functions change with environmental context (salinity, organic enrichment, seawater acidification and temperature), and that changes in the ecosystem processes known to mediate functions do not necessarily reflect a change in functioning. In addition intra-species variation in functional activity indicates that it may not be appropriate for all members of a population to be ascribed to the same functional group. This thesis highlights a need to test that different functional groups reflect different effects on ecosystem functioning. Further it shows that functional groups are not constant, individuals within populations are not necessarily functional equivalents, and that individuals have the capacity to change their contributions to ecosystem functions and processes. Future research needs to acknowledge and incorporate both biotic and abiotic sources of variability in species effects on ecosystem functions and processes.
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Fallesen, Grethe. "The ecology of macrozoobenthos in Arhus Bay, Denmark." Thesis, University of Stirling, 1994. http://hdl.handle.net/1893/21608.
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The aim of this thesis has been to: 1) assess the state of pollution in the two study areas and relate them to recent changes found in the Kattegat - Belt Sea area; 2) examine the observed spatial and temporal variability in species composition, abundance and biomass in Arhus Bay and the Formes area and relate the variability to antropogenic and natural causes; 3) discuss and assess methods, particularly for the estimation of secondary production and the use of multivariate analyses as methods for examining changes in macrozoobenthic communities. Macrozoobenthos were sampled at 15 stations in Arhus Bay, Denmark from 1985 to 1991 while data from Formes (reference area) included 55 sampling stations from 1986 to 1990. Monthly sampling took place at one station in Arhus Bay in 1990 and 1991. The two study areas are both situated on the eastcoast of Jutland in the Kattegat - Belt Sea area at 13-17 m depth and both receive waste water from long sea outfalls. Although both areas are Subjected to salinity stratification for most of the year, the exposed position of the Formes area on the open Kattegat coast prevents it from suffering from severe oxygen deficiencies, unlike the Arhus Bay which is a sheltered, semi-enclosed sedimentation area where oxygen concentrations in the bottom water can be very low. At Formes the sediment is sandy while it is silty in Arhus Bay. The spatial and temporal variability in the benthos in Arhus Bay could to a great extent be explained by the variation in 7 important species: Abra alba, Corbula gibba, Mysella bidentata, Nepthys hombergii, N. ciliata, Ophiura albida and Echinocardium cordatum. The fluctuations in the number and biomass of A. alba had a pronounced effect on the total abundance and biomass in Arhus Bay. The severe winter of 1986/87 with low temperatures and oxygen depletion under the ice cover practically eliminated A. alba from the bay. A. alba quickly recolonized the area and was found in high numbers in 1988. Studies of growth of A. alba in 1990 and 1991 showed that by the end of 1990 the population had reached an average length of 10 mm while the average shell length was only 5 mm by the end of 1991. The difference between the two years could be attributed to the difference in sedimentation of phytoplankton from the water column. As in other parts of the Kattegat - Belt Sea area, Arhus Bay has experienced low oxygen concentrations in the bottom water in late summer early autumn throughout the 1980s. Only the oxygen depletion under the ice cover in early spring 1987 and the local oxygen deficiencies south of the outlet in 1989 and 1990 actually killed parts of the benthic fauna. Apart from 1981, the oxygen deficiencies have thus been less severe in Arhus Bay than in other parts of the southern Kattegat in the 1980s. The number of species, abundance and biomass decreased at Fornres from 1980 to 1985 while the discharge of BOD was fairly constant during the same period. From 1986 there was a slight decrease in the discharge of BOD but a considerable increase in the number of species, abundance and biomass. At least for the second half of the 1980s there was no straightforward relation between the organic enrichment from the outlet and species composition, abundance and biomass and suggests that other factors are also important influencing the fluctuations in the benthic fauna. Estimates of total secondary community production were found to be very dependent on the method used. The method described by Brey (1990) was found acceptable for estimating secondary production in Arhus Bay but care should be exercised when comparisons are made with other areas where different methods have been used to estimate production. Secondary production was estimated more accurately for some of the abundant species in Arhus Bay on the basis of monthly samplings by the method described by Crisp (1984). Among the multivariate analyses the Detrended Correspondence Analysis (DCA) and nonmetric Multidimensional Scaling (MDS) proved to be the most successful with the Arhus Bay and Fornes data sets. Two Way INdicator SPecies ANalysis (TWINSPAN) did not work well with the Fornes data because it imposed discontinuities on data sets with continous variation in distribution of species among samples. As community types existed to a certain degree in Arhus Bay TWINSPAN worked well with these data. DCA and MDS were found to be useful techniques for analysing large data sets because they can summarize the data matrices to a manageable form and find possible patterns in the data sets. The results of the analyses can then be used as starting point for more detailed investigations of single species/samples or groups of species/samples. By using different transformations of the raw data the role of dominant or rare species can be assessed. A major 'problem in the assessment of multivariate techniques is the lack of external standards to compare with. The results of multivariate analyses must therefore be assessed critically on the basis of a careful examination of the species list combined with the knowledge and experience of the investigator. The methods used all had their advantages and limitations but each of the different methods added some important information to the picture of the benthic community in Arhus Bay and Fornes. It was thus an considerable advantage to use several different methods to analyse the spatial and temporal variability in the benthic fauna in relation to antropogenic and natural causes.
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Snook, Deborah Louise. "Macroinvertebrate communities in alpine glacier-fed streams : the Taillon catchment in the French Pyrenees." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343507.
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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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Chan, King-tung, and 陳勁東. "Multivariate analysis of benthic macroinvertebrate communities of HongKong streams." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213911.
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Schriever, Carola Alexandra. "Modeling ecological risk of runoff for benthic invertebrates in agricultural landscapes /." Leipzig : UFZ, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015694027&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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李嵐 and Laam Li. "Effects of hypoxia on marine benthic communities : from bacteria to invertebrates." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193402.
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Because of the eutrophication resulting from increasing anthropogenic activities, hypoxia (i.e. dissolved oxygen < 2.8 mg O2 L-1) is on the rise globally. The objective of this research was to understand more about the effects of hypoxia on the marine benthic communities. Particularly, it focused on the latent effects and indirect effects of hypoxia by investigating how early exposure to hypoxia affect the later life stage of a marine gastropod Crepidula onyx, and how hypoxia alter the bacterial composition of biofilms and the subsequent larval settlement of marine invertebrates.
In the first study, the larvae of C. onyx were exposed to 2, 3, and 6 mg O2 l-1. Under low food concentration (Isochrysis galbana at 1 × 105 cells l-1), larvae in both hypoxic treatments (2 and 3 mg O2 l-1) required a longer time to become competent to metamorphose. But when they did, they had a similar size and total lipid content to the control larvae. Moreover, the latent effects of early hypoxic exposure on the juvenile growth were evident. After 2 weeks development in field, the growth rate, mean dry weight and filtration rate of juveniles were significantly reduced in the hypoxic treatments. However, there was no discernible effect on larvae or juveniles when the food concentration during the larval stage was doubled (I. galbana at 2 × 105 cells l-1), suggesting that the latent effects of hypoxia can be offset by larval access to high algal concentration.
In the second study, the biofilms were exposed to hypoxia and normoxia in microcosms for up to 7 days, and their bacterial community composition was analysed by terminal-restriction fragment length polymorphism (T-RFLP). The results suggested that hypoxia altered the bacterial community structure within biofilms, and the difference between the hypoxia and normoxia treatments increased through the length of exposure period. The resulting changes in biofilms did not alter the larval settlement response of a model species (i.e. C. onyx) in laboratory assays. Nevertheless, when the biofilms were deployed in the field to allow natural larval settlement and recruitment, biofilms that had been exposed to hypoxia altered the overall larval settlement pattern of different marine invertebrates, potentially leading to a shift in the benthic invertebrate community.
This research suggested that periodic hypoxic events and the resulting exposure of organisms to hypoxia during their early development might have effects that persist across the life history. Moreover, it highlighted the possibility that the effects of hypoxia on species composition and structure of benthic invertebrate communities might be mediated through changes in biofilms and subsequently larval settlement and recruitment. To conclude, this research demonstrated that hypoxia could affect the growth in the later life stages of marine invertebrates and the recruitment of the benthic communities.published_or_final_version
Biological Sciences
Master
Master of Philosophy
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Meyer, Kirstin S. "Community assembly of benthic invertebrates on island-like marine hard substrata." Thesis, University of Oregon, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10192050.
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Most of the seafloor is soft sediment, so hard substrata are isolated and island-like. In this dissertation, I explore how species distribution patterns on isolated marine hard substrata resemble terrestrial island communities, drawing on classical island biogeography theory and assembly rules, and describe how benthic invertebrate communities assemble in these island-like habitats. Higher species richness occurred on larger substrata (dropstones and shipwrecks), paralleling terrestrial island communities. However, while larger islands have greater habitat diversity and primary productivity, marine hard substrata are simpler habitats. Greater elevation in the benthic boundary layer may expose fauna to faster current, higher food supply and larval flux. Substrata located closer together had more similar communities, another pattern that resembles terrestrial islands. Dropstone fauna had a clumped distribution, indicating that larvae may disperse among substrata located close together, resulting in similar communities. In Svalbard fjords, benthic megafaunal communities were significantly different between Arctic- and Atlantic-influenced fjords. Depth and temperature had the greatest influence, with the highest diversity occurring in cold Rijpfjorden and on the north Svalbard shelf. Recruitment in Svalbard fjords was spatially and temporally variable, with lower recruitment in Rijpfjorden than in Atlantic-influenced fjords and lower recruitment at greater depth. Most of the recruits in Svalbard fjords were fast-growing, poor-competitive opportunists. On shipwrecks, communities showed two mechanisms of colonization: mobile fauna with long-dispersing planktotrophic larvae, and encrusting fauna with lecithotrophic larvae. Encrusting species reproduce asexually to cover the wreck surface, and philopatry may build up dense populations, leading to uneven communities. On terrestrial islands, non-random co-occurrence is attributed to interspecific competition, but for marine substrata, there may not be a relationship. Fauna were distributed randomly on settlement plates in Svalbard fjords, even when interspecific competition was observed. On dropstones, some morphotypes co-occurred non-randomly in the absence of overgrowth competition. Non-random co-occurrence on isolated marine hard substrata may be a result of restricted larval dispersal (for pairs co-occurring less than by chance) or epibiontism (for pairs co-occurring more often than by chance). While species distribution patterns on island-like marine hard substrata resemble terrestrial islands, the mechanisms are not necessarily the same.
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Brink, Laura Ann. "Cross-shelf transport of planktonic larvae of inner shelf benthic invertebrates." Thesis, Thesis (M.S.)--University of Oregon, 1996, 1997. http://hdl.handle.net/1794/10073.
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Meyer, Kirstin. "Community assembly of benthic invertebrates on island-like marine hard substrata." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20686.
Full textAbstract:
Most of the seafloor is soft sediment, so hard substrata are isolated and island-like. In this dissertation, I explore how species distribution patterns on isolated marine hard substrata resemble terrestrial island communities, drawing on classical island biogeography theory and assembly rules, and describe how benthic invertebrate communities assemble in these island-like habitats.
Higher species richness occurred on larger substrata (dropstones and shipwrecks), paralleling terrestrial island communities. However, while larger islands have greater habitat diversity and primary productivity, marine hard substrata are simpler habitats. Greater elevation in the benthic boundary layer may expose fauna to faster current, higher food supply and larval flux. Substrata located closer together had more similar communities, another pattern that resembles terrestrial islands. Dropstone fauna had a clumped distribution, indicating that larvae may disperse among substrata located close together, resulting in similar communities.
In Svalbard fjords, benthic megafaunal communities were significantly different between Arctic- and Atlantic-influenced fjords. Depth and temperature had the greatest influence, with the highest diversity occurring in cold Rijpfjorden and on the north Svalbard shelf.
Recruitment in Svalbard fjords was spatially and temporally variable, with lower recruitment in Rijpfjorden than in Atlantic-influenced fjords and lower recruitment at greater depth. Most of the recruits in Svalbard fjords were fast-growing, poor-competitive opportunists. On shipwrecks, communities showed two mechanisms of colonization: mobile fauna with long-dispersing planktotrophic larvae, and encrusting fauna with lecithotrophic larvae. Encrusting species reproduce asexually to cover the wreck surface, and philopatry may build up dense populations, leading to uneven communities.
On terrestrial islands, non-random co-occurrence is attributed to interspecific competition, but for marine substrata, there may not be a relationship. Fauna were distributed randomly on settlement plates in Svalbard fjords, even when interspecific competition was observed. On dropstones, some morphotypes co-occurred non-randomly in the absence of overgrowth competition. Non-random co-occurrence on isolated marine hard substrata may be a result of restricted larval dispersal (for pairs co-occurring less than by chance) or epibiontism (for pairs co-occurring more often than by chance). While species distribution patterns on island-like marine hard substrata resemble terrestrial islands, the mechanisms are not necessarily the same.
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Khan, Muhammad Irfan. "A lotic microcosm for ecological and ecotoxicological studies on benthic macroinvertebrates." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320214.
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Word, Jack Q. "The infaunal trophic index, a functional approach to benthic community analyses /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/5289.
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Hung, Oi Shing. "Effects of environmental factors on biofilms and subsequent larval attachment of benthic marine invertebrates /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202007%20HUNG.
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Taboada, Moreno Sergio. "Antarctic marine benthic invertebrates: chemical ecology, bioactivity and biodiversity / Invertebrados bentónicos marinos de la Antártida: ecología química, bioactividad y biodiversidad." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/83921.
Full textAbstract:
Esta tesis cubre diferentes aspectos de los invertebrados marinos bentónicos de la Antártida. Se trata de una tesis multidisciplinar presentada en formato artículos en la que se hacen las siguientes aportaciones: (i) por un lado se hace una revisión de los productos naturales de origen animal y vegetal descritos hasta Mayo de 2007 en las aguas de la Antártida. En dicha revisión se hace especial énfasis en el papel que juegan los productos naturales en el contexto de su ecosistema; (ii) se aportan también datos sobre experimentos de repelencia alimentaria en los que se utilizaron extractos lipofílicos de invertebrados bentónicos de 2 zonas muy poco estudiadas (este del Mar de Weddell e Isla de Bouvet). En dichos experimentos, que se llevaron a cabo utilizando depredadores simpátricos, se ha demostrado que algo más de la mitad de los invertebrados testados poseen defensas químicas que los defienden frente a posibles depredadores. En algunos de estos casos las defensas químicas parecen localizarse en las partes más expuestas/vulnerables de los organismos testados; (iii) uno de los artículos de esta tesis confirma el potencial antitumoral que tienen los invertebrados marinos bentónicos antárticos y sub-antárticos. Se trata del estudio antitumoral más grande que jamás se haya hecho en este área con resultados muy prometedores para phyla como Chordata, Porifera y Cnidaria, entre otros; (iv) por último se describen un total de 4 nuevas especies de anélidos poliquetos de las aguas someras de la Antártida. Dichos organismos pertenecientes a las familias Cirratulidae (1 especie del género Cirratulus), Dorvilleidae (2 especies del género Ophryotrocha) y Siboglinidae (1 especie del género Osedax), fueron descritos a partir de huesos de ballena colocados experimentalmente en las aguas de Isla Decepción (Islas Shetland del Sur). Estos hallazgos confirman la importancia que los huesos de ballena pueden tener en el contexto de las aguas de poca profundidad de la Antártida.The Thesis entitled “Antarctic marine benthic invertebrates: chemical ecology, bioactivity and biodiversity" covers different aspects related to Antarctic marine benthic invertebrates. This is a multidisciplinar thesis comprising several scientific papers making the following contributions: (i) on the one hand it revises the described Antarctic marine natural products derived from animals and algae up to May 2007. In this revision, special emphasis is given to the role that these natural products play in their ecosystem; (ii) this thesis also provides data from feeding repellent experiments using lipophilic extracts from benthic invertebrates from two poorly known areas (eastern Weddell Sea and Bouvet Island). These experiments, carried out using sympatric predators, showed that more than half of the invertebrates tested possess chemical defenses against possible predators. In some of the cases, these defenses seem to be located in the most exposed/vulnerable parts of the organisms; (iii) one of the papers included in this thesis confirms that marine benthic invertebrates from Antarctic and sub-Antarctic waters have an interesting antitumoral potential. This work is the largest carried out in the area with very promising results for phyla such as Chordata, Porifera, and Cnidaria, among others; (iv) finally, this thesis comprises the description of 4 new species of annelid polychaetes from the Antarctic waters. These organisms belong to the families Cirratulidae (1 species from the genus Cirratulus), Dorvilleidae (2 species from the genus Ophryotrocha) and Siboglinidae (1 species from the genus Osedax), which were described from whale bones experimentally deployed in Deception Island (South Shetland Islands). These findings confirm the importance that whale bones may have in the Antarctic shallow-waters context.
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Thornton, Ann. "The impact of green macroalgal mats on benthic invertebrates and overwintering wading birds." Thesis, Bournemouth University, 2016. http://eprints.bournemouth.ac.uk/24874/.
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A consequence of increased nutrient levels within an estuarine ecosystem is the development of green macroalgal blooms or ‘mats’. These mats can cover extensive areas of estuarine intertidal habitats and have biomass >1 kg m-2 (wet weight). One of the key metrics for assessment of the ecological condition status of estuarine features in Europe is the extent and biomass of macroalgal mats. The aim of this research is to establish whether the development of green macroalgal mats affects feeding relationships between invertebrate assemblages and overwintering migratory wading birds in Poole Harbour - a temperate estuarine ecosystem on the south coast of England. Poole Harbour is designated for its populations of overwintering migratory wading birds. As such, any decline in wading bird numbers as a result of nutrient enrichment affecting their food supply or altering feeding behaviour, would result in sanctions under current legislation. This field research consisted of three main objectives: 1) Measuring the biomass and extent of the macroalgal mat within Poole Harbour. 2) Analysing any changes to the benthic invertebrate community under varying macroalgal mat densities. 3) Observing and recording the behaviour and feeding success of key wading bird species; in particular how they responded to changes in prey availability and varying levels of macroalgal mat coverage. Samples of macroalgal mat were taken monthly or bi-monthly on mudflats at four locations around the harbour over two years and wet weight biomass was recorded. Wading bird invertebrate prey availability was measured using benthic core samples taken at upper, mid, and lower shore levels at three key sites. Invertebrate size- classes were recorded and converted into available energy (kJ m-2) according to the preferred diet of each of the five wading bird species studied. Observations of wading bird behaviour were recorded over two overwintering periods (September – March). Digital video recordings were taken of different wading bird species’ feeding behaviour and success on varying levels of macroalgal mat coverage. Coverage by macroalgal mats was high (>50%) with dense patches persisting into autumn. Biomass of algae reached 1 kg m-2 at each of the sites during both years with two sites exceeding 2 kg m-2 (wet weight) in 2013; although that level was not maintained throughout the summer growth period. The invertebrate community was transformed under increased algal biomass within an increase in abundance (m-2) of smaller less energy-dense species when algae reached ~800 g m-2 (wet weight). Variation in overall invertebrate community assemblage between benthic samples was best explained by algae biomass; either singularly or in combination with % organic matter. This pattern was repeated with an initial increase in available energy (kJ m-2) within each bird species preferred prey under lower macroalgal mat biomass (~800 g m-2 wet weight) followed by a decline as algae biomass increased. During autumn, when large areas of macroalgal mat were still visible, foraging behaviour by some wading bird species varied under different levels of algae coverage. Some wading bird species’ behaviour also varied in winter on areas which had been covered by algae during the previous growth season. The current macroalgal mat biomass threshold of concern under SSSI Conditions Assessments is 2 kg m-2 (wet weight). Results suggest that the impact from macroalgal mats in Poole Harbour is evident at a biomass lower than 2 kg m-2 (wet weight); supporting a lowering of this threshold to 1 kg m-2. An increase in abundance of smaller invertebrates has resulted in a decline in energy available for the wading birds’ preferred diet. Observations suggest that wading birds may be adapting to these changes with some species appearing to be feeding on smaller, lower-quality prey (i.e. smaller worms/bivalves) and other species feeding on prey found on the surface of the macroalgal mat. Adaptations are site-specific in response to conditions within individual bays but consistent between shore levels within each bay.
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Stubbington, Rachel. "The hyporheic zone as a refugium for benthic invertebrates in groundwater-dominated streams." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8376.
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A principal ecological role proposed for the hyporheic zone is as a refugium that promotes benthic invertebrate survival during adverse conditions in the surface stream. Whilst a growing body of work has examined use of this hyporheic refugium during hydrological extremes (spates, streambed drying), little research has considered variation in refugium use over prolonged periods including contrasting conditions of surface flow. In this thesis, benthic invertebrate use of the hyporheic refugium is considered at monthly intervals over a five-month period of variable surface flow, at nine sites in two groundwater-dominated streams, the River Lathkill (Derbyshire) and the River Glen (Lincolnshire). Conditions identified as potential triggers of refugium use included a flow recession and a high-magnitude spate on the Lathkill, and small spates and a decline in flow preceding localised streambed drying on the Glen. During flow recession, reductions in submerged habitat availability and concurrent increases in benthic population densities were dependent on channel morphology. An unusual paired benthic-hyporheic sampling strategy allowed the type of refugium use (active migration, passive inhabitation) to be inferred from changes in hyporheic abundance and the hyporheic proportion of the total population. Using this approach, evidence of active migrations into the hyporheic zone use was restricted to two instances: firstly, Gammarus pulex (Amphipoda: Crustacea) migrated in response to habitat contraction and increased benthic population densities; secondly, migrations of Simuliidae (Diptera) were associated with low-magnitude spates. Refugium use was site-specific, with refugial potential being highest at sites with downwelling water and coarse sediments. A conceptual model describing this spatial variability in the refugial capacity of the hyporheic zone is developed for low flow conditions. In some cases, hyporheic refugium use was apparently prevented by disturbance-related factors (rapid onset, high magnitude) regardless of the refugial potential of the sediments. The extension of the hyporheic zone's refugial role to include low flows highlights the need to explicitly protect the integrity of hydrologic exchange in river rehabilitation schemes. However, the limited capacity of the hyporheic refugium emphasizes the additional importance of maintaining habitat heterogeneity including multiple instream refugia.
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West, Fraser James Craig. "Interactions between marine benthic invertebrates and sediments in intertidal and deep sea environments." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395057.
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Bowden, David A. "Benthic assemblage development and larval ecology of marine invertebrates at Adelaide Island, Antarctica." Thesis, Open University, 2005. http://oro.open.ac.uk/54925/.
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This thesis describes the first regularly resurveyed study of marine benthic colonisation processes at a location within the Antarctic Circle (660 30' S). Invertebrate assemblages on hard substrata were studied at 8 m and 20 m depths at three locations near Rothera Point, Adelaide Island (670 34' S, 68° 07' W). Assemblages on natural substrata were surveyed photographically and by sampling of cryptic sessile fauna. Recruitment to upper and lower surfaces of artificial substrata was monitored at monthly intervals through 1.5 yr and subsequent survival and growth of sessile assemblages was monitored photographically over 3 yr. Planktonic larvae of benthic invertebrates were surveyed at monthly intervals through 1.5 yr. Recruitment took place throughout the year but was strongly seasonal in most taxa. Many sessile taxa recruited during winter; apparently in direct contrast to a general pattern of summer recruitment in temperate latitudes. All vagile taxa, by contrast, recruited in summer, regardless of developmental type or time of spawning. Rates of assemblage development, and maximum growth rates of individual species, were slow compared with temperate latitudes but a biotic and biotic disturbances caused realised growth rates to be highly variable at scales of m - km. Ice impacts affected substrata at 8 m but the establishment of assemblages at both depths was controlled principally by postsettlement mortality from biotic disturbances, particularly grazing by the urchinSterechinus neumayeri. Larvae were present in all months but most taxa showed strong seasonality of occurrence. Diversity of larval types was comparable with data from other Antarctic and temperate studies but abundances were higher than in a similar study at Signy Island (60043' S, 45° 36' W). The range of larval types, durations, and times of spawning argues against any strong selective pressures acting on developmental mode itself. Rather, the timing of settlement appears to be the characteristic of the life cycle that is most strongly selected for. It is suggested that differences between sessile and mobile taxa in the timing of settlement may be caused by the seasonal availability of food types for juvenile stages.
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Custer, Kevin Wayne. "FACTORS CONTROLLING NICKEL BIOAVAILABILITY AND EFFECTS ON BENTHIC INVERTEBRATES IN HARDWATER FRESHWATER STREAMS." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1364295154.
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Mayoral, Helen. "Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution and Abundance in a Gravel-bed River of the Southern Appalachians." Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/geosciences_theses/31.
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To determine the relationship between the abundance and density of benthic invertebrates, and the critical shear stress of individual grain sizes, a reach along Smith Creek, was divided into ten 2m x 2m quadrants. Within each quadrant, five randomly selected clasts for each grain size ranging from 2.26 to 25.6 cm were cleaned for benthic invertebrates. Wolman pebble counts for each quadrant were also conducted and used to determine the critical Shields stress per grain size fraction from the model given by Wiberg and Smith (1987) that explicitly accounts for particle hiding/sheltering effects in mixed-bed rivers. Particle entrainment values were then compared with estimated bankfull Shields stress values to determine sediment transport potential during bankfull flow. Invertebrate abundance was strongly positively correlated with critical Shields stress up to the 18.0 cm grain size, indicating a preference for certain grain sizes; while density was positively correlated with all grain sizes present.
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Foster, William J. "Palaeoecology of the late Permian mass extinction and subsequent recovery." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/5467.
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Climate warming during the latest Permian is associated with the most severe mass extinction event of the Phanerozoic, and the expansion of hypoxic and anoxic conditions into shallow shelf settings. Our understanding of the magnitude, pattern and duration of the extinction event and subsequent recovery remains equivocal. Evidence suggests that the action of waves provided an oxygenated refuge, i.e. ‘habitable zone’, above wave base that may be limited to high latitudes, in association with a faster pace of recovery. In addition, advanced recovery faunas have been documented from the Induan and there is evidence from the pelagic realm that further biotic crises may have delayed the recovery of benthic organisms coinciding with large carbon isotope perturbations at the Lower Triassic sub-stage boundaries. To test these hypotheses, novel palaeoecological data was collected from localities in Hungary, northern Italy, and Svalbard. To understand better the ecological impact of the extinction, a database of all known benthic marine invertebrates from the Permian and Triassic periods was created, with each taxon assigned to a functional group based on their inferred lifestyle. This study found that the skeletal and ichnofaunal assemblages consistent with advanced ecological recovery are limited to settings aerated by wave activity, which supports the habitable zone hypothesis. In the western Palaeotethyan sections it was found that the proximal end of the ‘habitable zone’ was limited by persistent environmental stress attributed to increased runoff that resulted in large salinity fluctuations, increased sedimentation rates and eutrophication creating an environment only favourable for opportunistic taxa. In the Tirolites carniolicus Zone, however, the ‘habitable zone’ expands into more proximal and offshore settings. This is associated with climate cooling in the late Spathian. The data also demonstrate that despite the taxonomic severity of the extinction, only one mode of life went extinct and only one subsequently evolved in the aftermath. Functional diversity was, however, reduced in particular regions and environmental settings, and recovery varied spatially and temporally. In western Palaeotethys, benthic communities record evidence for biotic crises, such as reduced tiering in the Smithian, associated with Early Triassic carbon isotope excursions, but, until the Spathian there was no significant change in the composition of the benthic faunas.
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Campbell, Rebecca Elisabeth. "Spatial pattern and community assembly: does the configuration of stream networks influence their community structure?" Thesis, University of Canterbury. School of Biological Sciences, 2011. http://hdl.handle.net/10092/5094.
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Dendritic stream networks are inherently spatially and hierarchically structured, but the effects of this structure on stream communities are largely unknown. My aim was to investigate spatial patterns in stream networks using extensive spatial sampling of both adult and benthic macroinvertebrates in four stream networks on the West Coast of the South Island, New Zealand. Using spatial modelling and analyses, I answered questions about appropriate spatial measurements to capture ecological processes in stream networks, metacommunity processes at different scales in space and time, and how local and regional processes interact to structure metacommunities in stream networks.
Spatial eigenfunction analyses showed that distance measures that explained most variance in stream macroinvertebrate communities were stream distance and weighted stream distance measures. They performed better than Euclidean distance to measure spatial structure that is ecologically
relevant to stream network communities. The spatial pattern of benthic
stream macroinvertebrates was stable over time, whereas community composition changed significantly, as shown by space-time interactions modelled by MANOVA-like redundancy analysis. Thus, spatial processes structuring stream metacommunities remained constant, in agreement with neutral model predictions. Network-scale properties, particularly flood disturbances, influenced the relative importance of spatial and environmental
variation in stream network metacommunities. Additionally, quantile regression indicated that three key variables, habitat size, isolation and local habitat conditions, jointly limited community structure in stream networks, providing empirical support for both island biogeography and metacommunity theories.
My study indicated that spatial structuring has an important influence on stream macroinvertebrate communities. The results contribute to broader ecological theory and understanding of community assembly by relating empirical results to theoretical predictions. In particular, they advance understanding of spatial processes in stream networks. The research also highlights a number of new methods, which were successfully applied to stream systems to elucidate complex spatial patterns.
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Lloyd, Natalie J. "Spatial autocorrelation of benthic invertebrate assemblages in two Victorian upland streams." Monash University, Dept. of Biological Sciences, 2002. http://arrow.monash.edu.au/hdl/1959.1/8428.
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Wahab, Md Abdul. "The ecology of benthic macro-invertebrates in earthen trout ponds at Howietoun, central Scotland." Thesis, University of Stirling, 1986. http://hdl.handle.net/1893/28840.
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An Investigation Into the ecology of benthic macro-invertebrates in earthen ponds subjected to intensive trout (Salmo trutta L.) culture practices at Howletoun, Central Scotland, was conducted between May 1984 and January 1986. Soil and water quality, seasonal changes in benthos, its role in the trout diet and the Interaction between fish and benthos were studied. Pond benthos mainly comprised 6 major groups including Oligochaeta. (10 species), Chironomldae (18 species), Molluscs and Hirudinea (2 species each) and an asellid and a sialid species. Oligochaeta formed 78 to 90% of benthic fauna, dominated by Tubifex tubifex. Limnodrilus hoffmeisteri, L. udekemianus and Psammoryctides barbatus, with an average population density of 68,400 - 191,200 worms mˉ², and exhibited peaks in summer and late autumn corresponding to two major breeding periods. The principal species of Chironomidae were Chironomus spp., Procladius spp. and Prodiamesa olivacea, with a population density of 5,400 to 14,900 ind. mˉ² and forming 7 to 13% of the total benthos with peaks in spring and autumn. Dry biomass of total benthos varied from 24-59 g mˉ² in the cultured ponds with oligochaetes accounting for 14-49 g mˉ² and chironomids 4-7 g mˉ². The mean annual dry weight production of total benthos varied from 130-215 g mˉ² in the cultured ponds, with oligochaete production of 94-160 g mˉ² and chironomid production of 20.6-33.5 g mˉ². An investigation into the ecology of benthic macro-invertebrates in earthen ponds subjected to intensive trout (Salmo trutta L.) culture practices at Howietoun, Central Scotland, was conducted between May 1984 and January 1986. Soil and water quality, seasonal changes in benthos, its role in the trout diet and the interaction between fish and benthos were studied. Pond benthos mainly comprised 6 major groups including Oligochaeta (10 species), Chironomidae (I8 species), Mollusca and Hirudinea (2 species each) and an asellid and a sialid species. Oligochaeta formed 78 to 90% of benthic fauna, dominated by Tubifex tubifex. Limnodrilus hoffmeisteri, L. udekemianus and Psammoryctides barbatus, with an average population density of 68,400 - 191,200 worms mˉ², and exhibited peaks in summer and late autumn corresponding to two major breeding periods. The principal species of Chironomidae were Chironomus spp., Procladius spp. and Prodiamesa olivacea, with a population density of 5,400 to 14,900 ind. mˉ² and forming 7 to 13% of the total benthos with peaks in spring and autumn. Dry biomass of total benthos varied from 24-59 g mˉ² in the cultured ponds with oligochaetes accounting for 14-49 g mˉ² and chironomids 4-7 g mˉ². The mean annual dry weight production of total benthos varied from 130-215 g mˉ² in the cultured ponds, with oligochaete production of 94-160 g mˉ² and chironomid production of 20.6-33.5 g mˉ². In an unstocked control pond the total production was 55 g mˉ², 35 g mˉ² of which was accounted for by oligochaetes and 8.06 g mˉ² by chironomids. Analyses of gut contents of the farmed trout showed that 12% of the diet by volume consisted of natural food, mainly benthos. Fish selectively fed on chironomid larvae, Mollusca, Asellus aquaticus and Sialis lutaria. Fish took maximum natural food in the morning and evening. Experimental enclosures to exclude fish from selected areas of the ponds demonstrated that number of species increased outside the enclosures but, except for chironomids, population density, biomass and production generally increased inside the enclosure. The possibility of explaining this result in terms of differential predation is discussed.
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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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Eivers, Rebecca. "The response of stream ecosystems to riparian buffer width and vegetative composition in exotic plantation forests." Thesis, University of Canterbury. Biological Sciences, 2006. http://hdl.handle.net/10092/1354.
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Riparian buffers along stream margins have been widely adopted as a management strategy to mitigate the adverse effects of plantation forestry on stream ecosystems. However, the efficacy of these riparian buffers can be jeopardised by variations in width, length, and vegetation which can range from native and exotic scrub (including bracken, gorse, broom and blackberry) to remnant beech forest. This thesis investigates the influence of riparian vegetation age and composition, on stream ecosystems within exotic pine plantations. Initially, a survey of 50 streams within pine forests of various ages and riparian composition was conducted at sites from mid-Canterbury to Hanmer Springs over the summer of 2004-2005. Additionally, terrestrial subsidies were compared between young pine, mature pine and indigenous forest streams to ascertain differences or similarities between vegetation types. A range of physico-chemical and biological characteristics were recorded, while vegetative age and composition with catchment, riparian buffer and reach scales were determined using GIS. Forestry activities were found to vary temporarily and tended to adversely impact upon streams where riparian buffers were narrow and lacked indigenous vegetation. Stream instability and sedimentation were consistently higher in catchments lacking indigenous riparian vegetation, and more markedly so in recently harvested catchments compared with more mature forests. Streams dominated by pine forests had finer substrates with higher water temperatures and levels of turbidity, while those dominated by indigenous forest had coarser substrates, higher flows and dissolved oxygen levels, and less in-stream debris. Benthic community composition was similar among sites, although taxonomic richness, EPT diversity, and invertebrate abundances were enhanced by indigenous riparian vegetation.
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Cowley, C. "The influence of road runoff on the benthic macro-invertebrates of an unpolluted chalk stream." Thesis, University of Westminster, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354965.
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Leung, Sze-lun. "Scale-dependent effects of spatial and temporal variability on benthic macroinvertebrate communities in Hong Kong streams /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25334542.
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Ford, Zackary L. "Impacts of suspended and deposited sediment on benthic invertebrates and fishes in a Missouri Ozark stream." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4550.
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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 (February 7, 2007) Includes bibliographical references.
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Demko, Jacqueline Ann. "Land Use, Stream Stability, and Benthic Invertebrates in a Dry Forest Watershed of Western Costa Rica." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6648.
Full textAbstract:
There is a paucity of data on dry forests, the most threatened biome in the tropics. The Nandamojo is a tropical dry forest watershed in Western Costa Rica that has been impacted by varying degrees of human induced modifications. This research was conducted to examine the influence of land use and channel characteristics on invertebrate communities within a sub basin of the Nandamojo watershed. This study addressed three hypotheses: (1) sites with low tree cover and small riparian buffer zones will have high erosion, (2) macroinvertebrate abundance will be lower at sites with low channel stability values, and (3) benthic macroinvertebrate abundance will be higher in years of high rainfall and flow regimes. Sites were established along three tributaries, which were surveyed in 2013 and 2015. Data were compared (1) along the length of respective tributaries and their elevation gradients, and (2) between survey years. Although Nandamojo is a mixed land use watershed, two of the four land uses were dominant; pasture and forest. Macroinvertebrate counts were statistically different across survey years and seasons. The abundance of macroinvertebrates was greatest on Tributary 3, where the dominant land use was forest. Regional interannual rainfall is suggested as a driving factor for interannual differences in macroinvertebrate abundance. Although results suggest that this sub basin is in good health, taking preventative action by developing a subbasin management plan is needed. As tropical dry forest is the most threatened forest biome, educating local residents not only about the numerous risks of human induced modifications such as forest to pasture land conversion, but also the corresponding importance of maintaining riverbank vegetation in headwater streams should be a foremost priority.
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Harwood, Amanda D. "What is the best chemical approach to estimate the bioavailability of pyrethroid insecticides to benthic invertebrates?" OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/469.
Full textAbstract:
The traditional approach for predicting the risk of hydrophobic organic contaminants in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects in organisms. This method is limited, however due to the plethora of variables that can influence bioavailability. Therefore, a matrix independent method of predicting bioavailability needs to be developed in order to be universally applicable. Solid phase microextraction (SPME) and Tenax are two commonly used bioavailability-based methods. While both SPME fiber and Tenax extractable concentrations can be correlated to tissue residues of aquatic species, the majority of this research (with a few exceptions) focuses on compounds that are not acutely toxic or biotransformed. Less is known about the potential applicability of these methods to predict bioaccumulation, and ultimately toxicity, for highly toxic, rapidly biotransformed compounds, such as pyrethroid insecticides. This class of compounds is of particular concern due to frequent environmental detection in sediments at concentrations lethal to benthic species. This research has four specific goals: Determining exposure conditions that may change the concentration on the SPME fibers at equilibrium (Chapter 2); Comparing the ability of SPME fibers and Tenax to predict the bioavailability of two pyrethroids (permethrin and bifenthrin) (Chapter 3); Developing bioavailability-based toxicity endpoints for bifenthrin using two aquatic species (Chapter 4); and, Validating these techniques using sediments from known contaminated field sites (Chapter 5). Overall this research was focused on comparing and contrasting the ability and applicability of SPME fibers and Tenax to adequately predict the exposure of pyrethroids under varying conditions. While comparing these two methods, they were optimized to better provide accurate predictions of bioavailability and toxicity for pyrethroids from sediments. Regardless of the fiber or animal density examined, the SPME fibers exposure did not significantly affect fiber concentrations for permethrin or DDE. Additionally, bioaccumulation of parent permethrin and bifenthrin was predicted using both SPME fibers and Tenax using 6 or 24 h extraction times. Further, a single regression model predicted bioaccumulation across compounds and species using Tenax extractable concentrations. Once demonstrated that these techniques could predict bioaccumulation, median lethal and effect levels were examined for bifenthrin and as expected the bioavailability-based endpoints were more uniform across sediments than use of whole sediment concentrations. Additionally, the relationships among the two methods were compared across multiple sediments. Despite the SPME fiber's ability to determine toxicity in laboratory sediments, the field validation study determined that lethal levels were often too low to detect on the SPME fibers using current methodologies, but Tenax extractable concentrations correlated to toxicity. Overall, while both methods could predict bioavailability, the limitations of SPME fibers including lower sensitivity, inability to function across compounds, and long equilibration time, made Tenax extraction a preferable method.
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McKenzie-Smith, Fiona Julie, and n/a. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland." Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030725.142256.
Full textAbstract:
Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them. Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface. Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought. The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively. Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters. Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the 'third' experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment. Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within 'ecological time' are perceived as critical to understanding the role of benthic sediment substratum.
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McKenzie-Smith, Fiona Julie. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366461.
Full textAbstract:
Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them.
Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface.
Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought.
The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively.
Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters.
Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the ‘third’ experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment.
Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within ‘ecological time’ are perceived as critical to understanding the role of benthic sediment substratum.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Faculty of Environmental Sciences
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Moore, Tom. "Nitrate-nitrogen effects on benthic invertebrate communities in streams of the Canterbury Plains." Thesis, University of Canterbury. Biological Sciences, 2014. http://hdl.handle.net/10092/9936.
Full textAbstract:
Aquatic ecosystems are especially vulnerable to human impacts associated with agricultural land-use, which provide multiple stressors altering community composition, important ecosystem functions and human valued properties of freshwaters. However, the increased occurrence of excessive levels of nitrate-nitrogen has raised major concerns about toxicity and stress on aquatic life, especially in regions such as the Canterbury Plains, New Zealand. The aims of this thesis were to identify nitrate-nitrogen effects on stream communities, and additionally provide field data to inform proposed national bottom lines for nutrients in New Zealand streams. A field survey was conducted on 41 small streams on the Canterbury Plains spanning a nitrate-nitrogen gradient (mean 0.4 – 11.3 mg/L). Spot nitrate-nitrogen was collected during and after the field survey to measure temporal variation in stream nitrate-nitrogen concentration for six months. This showed nitrate-nitrogen concentration varied between season and sub-region, where concentrations increased in winter and Ashburton had higher nitrate-nitrogen than Rangiora and Lincoln, respectively. These regimes of nitrate-nitrogen showed similar patterns in mean, median and maximum concentrations. To be confident my spot nitrate-nitrogen provided a true representation of long-term water chemistry, I compared Environment Canterbury 12 monthly data with my six monthly data in a sub-set of 15 sites. This comparison showed similar nitrate-nitrogen patterns and range of values between the two datasets. I then compared 12 common benthic invertebrate biotic metrics with my nitrate-nitrogen data and found none were correlated with this contaminant. For example, the Macroinvertebrate Community Index and quantitative variant (QMCI) derived to measure the response to organic pollution provided inconsistent results when applied to my streams. Nevertheless, gut content stoichiometry of the common mayfly grazer Deleatidium spp. indicated improvement in food quality (lower C:N ratio) with higher nitrate-nitrogen concentrations. These results indicated either nitrate-nitrogen does not alter invertebrate structural metrics across this nitrate-nitrogen gradient, or that these biotic metrics measure community structure aspects not affected by nitrate-nitrogen. I then investigated possible community composition patterns across the nitrate-nitrogen gradient. Unconstrained ordination (on presence/absence data) showed invertebrate communities at my sites were influenced primarily by discharge and shade, with the next most important driver being nitrate-nitrogen. A constrained ordination (on the same data) testing the singular effect of nitrate-nitrogen showed a marginally non-significant change in composition, with higher variability in community composition at higher nitrate-nitrogen concentrations. A further aim of my study was to test the draft nitrate-nitrogen bands proposed by Hickey (2013). These nitrate-nitrogen bands may advise guidelines to protect aquatic organisms as required by the National Policy Statement on Freshwater. Analysis of my invertebrate communities showed differences in composition, particularly at < 1 and > 6.9 mg/L bands. Several predatory caddisfly taxa: Triplectides, Neurochorema and Oeconesus were identified as potential indicator species of communities associated with low nitrate-nitrogen. These findings show that nitrate-nitrogen effects are difficult to detect, and that it is not the main driver of community composition in Canterbury streams. However, nitrate-nitrogen may be an important stressor for sensitive benthic invertebrate communities, as effects were observed on pollution tolerant organisms in this study. Therefore, this research has implications for freshwater ecologists and environmental managers striving to improve the health of streams on the Canterbury Plains.
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Rodrigues, Andreia do Carmo Martins. "Combined effects of invasive species and insecticide exposure on freshwater invertebrates." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22326.
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Doutoramento em BiologiaFreshwater invertebrate communities are often exposed to multiple stressors that can disrupt aquatic trophic chains and ecosystem functioning. Insecticide contamination and invasive species are two main anthropogenic stressors of concern in freshwaters. Understanding their combined effects to community structure and vital ecosystem functions present challenges for an improved ecological risk assessment. The main objective of this research was thus to investigate whether the deleterious effects of insecticide pollution may be mediated by the presence of alien invasive species. An integrative study was designed to assess the direct and indirect effects of these actual threats to freshwater benthic communities, from the individual towards the community and ecosystem levels with focus on detritus-based food webs. Chlorantraniliprole (CAP), an anthranilic diamide was selected as model compound due to its novel mode of action that confers specificity for ryanodine receptors of insects. Plus, CAP neurotoxicity can potentially disrupt individual behaviour and chemical communication among freshwater species. In a first step, CAP toxicity was assessed and compared with that from a broad-spectrum pyrethroid. Although CAP revealed less toxicity towards the selected species in comparison with the pyrethroid esfenvalerate (ESF), environmentally relevant concentrations of both insecticides disrupted the feeding behaviour of the shredder Sericostoma vittatum and impaired the development of the collector Chironomus riparius. Further, metabolic costs and sub-organismal effects due to insecticide-induced stress were also assessed with different biochemical biomarkers, revealing high energetic costs in exposed organisms. Two biotic factors of high ecological relevance, predation and resource quality, were selected and effects of two widely distributed invasive species (Procambarus clarkii and Eucalyptus globulus) were also considered. Multiple stressors exposures were then performed in microcosms systems with tri-trophic simplified detritus-based food webs to evaluate effects on leaf decomposition, C. riparius development and shredder-collector interactions. In a first trial, combined effects of CAP exposure and predation risk were tested. Shredders presence drastically increased leaf decomposition, but CAP exposure decreased this ecosystem process. CAP toxicity, predation risk and shredders presence independently lead to decreases on C. riparius growth. Additionally, in similar assays, alder and eucalypt leaf decomposition was reduced under predation risk, impairing larvae growth, being this effect exacerbated in the presence of less nutritive eucalypt leaves. In both assays, C. riparius growth was reduced in the presence of the shredders, suggesting a competition between these species, irrespective of CAP exposure or predation risk. Lastly, freshwater benthic communities were exposed to CAP and invasive species presence in mesocosms systems allowing to test the different combinations of stressors under a more complex and realistic exposure scenario. Community responses to CAP were assessed in the presence of leaf litter of different nutritional value (native A. glutinosa vs invasive E. globulus leaves) and the presence of different predators (native dragonfly Cordulegaster boltonii vs invasive crayfish P. clarkii). A path analysis using structural equation modeling (SEM), was applied to identify, quantify and discriminate between the strength of direct and indirect effects of all stressors and their combination on community structure (macroinvertebrate abundances) and ecosystem function (leaf decomposition and primary production). Environmentally relevant exposure to CAP, presence of crayfish and eucalypt leaves all contribute to changes on macroinvertebrate abundances. Crayfish presence mediated CAP toxicity to collectors and grazers. Shredders and collectors survival was reduced in treatments with eucalypt leaves which also presented lower leaf decomposition in comparison with streams with alder leaves. CAP toxicity towards collectors was magnified in the streams with Eucalyptus leaves. Density-mediated effects were observed and reductions of grazer species lead to increased primary production. In summary, this research showed that predator identity and detritus quality can mediate the effects of insecticide contamination on structural and functional endpoints in benthic freshwater communities and highlights the value of incorporating biotic stressors in ecotoxicological experiments. The present thesis is a contribution to the complex task of assessing the effects of pesticides under a more natural and complex scenario of exposure that is, nevertheless, critical for an effective risk management of freshwater ecosystems near agricultural areas.
As comunidades de invertebrados de água doce estão frequentemente expostas a múltiplas pressões que podem perturbar as cadeias tróficas e funções do ecossistema. A contaminação por inseticidas e a presença de espécies invasoras são duas das principais pressões antropogénicas nestes sistemas. Entender os seus efeitos combinados na estrutura e funções das comunidades é um dos atuais desafios para uma melhor avaliação de risco ecológico. O principal objetivo deste estudo foi avaliar se os efeitos deletérios da poluição por inseticidas são mediados pela presença de espécies invasoras. Para tal, foi realizado um estudo integrativo dos efeitos diretos e indiretos destas ameaças para as comunidades bentónicas de água doce, medindo respostas ao nível do indivíduo, da comunidade e ecossistema, com foco em cadeias alimentares de detritos. Chlorantraniliprole (CAP), uma diamida antranílica, foi usado como composto modelo devido ao seu modo de ação que lhe confere especificidade pelos recetores de rianodina de insetos. Além disso, a neurotoxicidade do CAP pode perturbar o normal comportamento e comunicação química entre espécies. Primeiramente, a toxicidade do CAP foi avaliada e comparada com a de um piretróide de amplo espectro. Embora o CAP se tenha revelado menos tóxico para as espécies estudadas que o esfenvalerato (ESF), concentrações ambientalmente relevantes de ambos os inseticidas inibiram a alimentação do fragmentador Sericostoma vittatum e diminuíram o desenvolvimento do coletor Chironomus riparius. Os custos metabólicos e os efeitos ao nível suborganismal foram avaliados através de diferentes biomarcadores bioquímicos, revelando elevados custos energéticos para estes invertebrados quando sob stress químico. Os efeitos de dois fatores bióticos de elevada relevância ecológica, predação e qualidade do recurso alimentar, foram estudados e avaliados alterando a sua identidade por duas espécies invasoras (Procambarus clarkii e Eucalyptus globulus) amplamente distribuídas na Europa. Exposições a múltiplos stressores foram então realizadas em sistemas de microcosmos com cadeias alimentares de detritos simplificadas para avaliar a decomposição de folhada, o crescimento de C. riparius e alterações nas interações fragmentador-coletor. Num primeiro ensaio, foram avaliados os efeitos combinados da exposição a CAP e risco de predação. A presença de fragmentadores aumentou consideravelmente as taxas de decomposição da folhada, mas a contaminação por CAP teve o efeito contrário. A toxicidade do CAP, o risco de predação e a presença de fragmentadores contribuíram para o decréscimo do crescimento de C. riparius. Em ensaios similares, a decomposição da folhada de amieiro e eucalipto foi reduzida sob risco de predação, diminuindo o crescimento das larvas, sendo este efeito exacerbado com eucalipto, de menor valor nutricional. Em ambos os ensaios, o crescimento de C. riparius foi reduzido na presença dos fragmentadores, sugerindo uma competição entre estas espécies, independentemente da exposição a CAP ou presença do predador. Por fim, comunidades bentónicas de água doce foram expostas a CAP e presença de espécies invasoras em mesocosmos, permitindo testar as diferentes combinações de stressores sob um cenário de exposição mais relevante. As respostas das comunidades ao CAP foram avaliadas na presença de folhada de diferentes valores nutricionais (da nativa Alnus glutinosa vs folhas da invasora E. globulus) e na presença de diferentes predadores (odonata nativo Cordulegaster boltonii vs lagostim invasor P. clarkii). Para identificar, quantificar e discriminar a magnitude dos diversos efeitos diretos, indiretos e combinados dos vários stressores sobre a estrutura da comunidade (abundância de macroinvertebrados) e função do ecossistema (decomposição foliar e produção primária), utilizou-se um método de análise de equações estruturais (SEM). Concentrações ambientalmente relevantes de CAP, a presença do lagostim e das folhas de eucalipto, contribuíram para alterações na abundância de macroinvertebrados. A presença do lagostim mediou os efeitos tóxicos do CAP para coletores e herbívoros. A sobrevivência dos fragmentadores e coletores foi reduzida nos tratamentos com folhada de eucalipto, que por sua vez também apresentaram menor decomposição em comparação com os rios com folhada de amieiro. A toxicidade do CAP para os coletores foi magnificada em rios com eucalipto como recurso alimentar. Efeitos mediados pela densidade foram observados através da redução de herbívoros que levou ao aumento de produção primária. Em síntese, este estudo demonstra que a identidade do predador e a qualidade dos recursos alimentares podem mediar os efeitos da contaminação por inseticidas em parâmetros estruturais e funcionais das comunidades bentónicas de água doce e destaca o valor da incorporação de stressores bióticos em testes ecotoxicológicos. A presente tese é um contributo para a complexa tarefa de avaliar os efeitos dos pesticidas considerando cenários de exposição ecologicamente relevantes que é, no entanto, crítica para uma avaliação de risco eficaz em ecossistemas de água doce perto de áreas agrícolas.
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Hamelin, Kayla. "Effects of thermal effluent on the diversity and distribution of benthic invertebrates in the St. Lawrence River." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123083.
Full textAbstract:
Temperature is a primary physical constraint on the distribution and abundance of aquatic organisms. Increasingly, human activities modify natural thermal regimes of aquatic systems, thereby altering the composition and structure of the organismal community. For decades, the Gentilly-2 Nuclear Power Plant (G2NPP) in Bécancour, QC, has discharged coolant water into the St. Lawrence River at temperatures more than 10ºC above ambient. My study aimed to quantify how the diversity, composition, and abundance of the St. Lawrence benthic macroinvertebrate community has been altered by G2NPP thermal effluent. Benthic samples were collected at sites along the thermal gradient downstream of G2NPP in May and September 2012. Environmental predictors varying with distance downstream of G2NPP (e.g., temperature, depth, flow rate) were recorded at each station. Macroinvertebrate diversity and abundance were measured for each site and analyzed in relation to local environmental variables. Taxonomic richness and abundance (density and biomass) were elevated close to the power plant, but these patterns were best explained by environmental variables such as depth and sediment type. Taxonomic evenness was reduced in the warmest sites, and this pattern was driven by a few highly tolerant taxa, including thermophilic invasive species like the Asian clam, Corbicula fluminea, which was amongst the most dominant species in terms of abundance and biomass. Despite the strong thermal gradient at G2NPP, diversity indices and characteristics of community composition primarily reflected abiotic habitat characteristics other than temperature, whereas temperature was an important predictor only for a minority of taxa, like C. fluminea. With the closure of G2NPP in December 2012, and the subsequent eradication of cold-sensitive C. fluminea, these results provide a baseline for monitoring the succession of the benthic community in future years.La température de l'eau est une composante principale dans la distribution et l'abondance des organismes aquatiques. Aussi, l'essor des activités anthropogeniques modifient les régimes thermiques des écosystèmes aquatiques et changent par le fait même la composition et la structure des communautés d'organismes. Pendant des décennies, la centrale nucléaire Gentilly-2 (CNG-2) à Bécancour, QC, a déchargé ses eaux de refroidissment dans le Fleuve St- Laurent à des températures supérieures à 10ºC la température ambiante du cours d'eau. L'objectif de mon étude a été de quantifier les patrons de diversité, de composition, et d'abondance de la communauté benthique de macroinvertébrés du Fleuve St-Laurent affectée par l'effluent thermique de la CNG-2. Des échantillons benthiques ont été récoltés à différentes stations le long du gradient thermique en aval de la CNG-2 en mai et septembre 2012. Les variables environnementales qui variaient en fonction de la distance par rapport à la source de l'effluent thermique (e.g., température, profondeur, courant) ont été enregistrés à chaque station. La diversité et l'abondance des macroinvertébrés ont été mesurées à chaque station et analysées par rapport aux variables environnementales locales. La richesse taxonomique et l'abondance (densité et biomasse) étaient élévées près de la centrale nucléaire, mais ces observations étaient davantage liées à des variables environnementales comme la profondeur et le type de sédiments. La regularité taxonomique était réduite aux stations les plus chaudes expliquée par la présence de quelques taxa seulement tolérant aux températures élevées, dont des éspèces envahissants thermophiles comme la petite corbeille d'Asie, Corbicula fluminea, qui était parmi les plus dominantes en termes d'abondance et de biomasse. Malgré le gradient thermique prononcé à la CNG-2, les indices de diversité et les caractéristiques de la composition de la communauté benthique reflètent essentiellement l'importance de caractéristiques abiotiques de l'habitat autres que la température, une componsante importante pour une minorité d'espèces seulement, telle C. fluminea. Avec la fermature de la CNG-2 en décembre 2012, et l'éradication de C. fluminea, les resultats présentés seront une référence au cours des prochaines années quant au suivi de la succession de la communauté benthique.
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Strachan, Maia Fiona. "Studies on the impact of a water-based drilling mud weighting agent (Barite) on some Benthic invertebrates." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2334.
Full textAbstract:
A comparative study was carried out to observe effects of standard grade and fine grade barite on the filtration rates of four suspension feeding bivalves, Modiolus modiolus, Dosinia exoleta, Venerupis senegalensis and Chlamys varia. Standard grade barite, the most commonly used weighting agent in water-based drilling mud, was responsible for altering the filtration rates of the four bivalve species and damaging the gill structure. The four bivalves were exposed to 0.5mm, 1.0mm and 2.0mm daily depth equivalents of standard grade barite, which permanently remained in suspension. All three barite levels altered the filtration rates leading to 100% mortality. The horse mussel, Modiolus modiolus was the most tolerant to standard barite with the scallop, Chlamys varia the least tolerant. Fine grade barite, at a 2mm daily depth equivalent, also altered the filtration rates of the four bivalve species, but only affected mortality of Venerupis senegalensis, with 60% survival at 28 days. In-vivo studies showed damage to the gills, ranging from displaced inter-lamellar junctions to the deletion of large parts of demibranch. Post-mortem microscopy studies showed damage to individual filaments with a marked reduction in the active surface area of the gill. Field studies have shown that the presence of standard grade barite is not acutely toxic to seabed fauna but does alter benthic community structure when it is persistent.
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Aigbavbiere, Ernest. "How does predation from fish influence the benthic invertebrates’ species composition in the Phragmites australis and Chara vegetation of Lake Takern?" Thesis, Linköpings universitet, Ekologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72643.
Full textAbstract:
Predation is one of the important selective factors that regulate the species composition of benthic invertebrate communities. The study objective was to investigate the invertebrate distribution in two contrasting habitats in Lake Takern, southern Sweden, submerged Chara vegetation and emergent Phragmites australis vegetation, and to investigate the influence of predation from fish on certain invertebrates. Laboratory studies were used to estimate handling time and the intake rate (mg/sec) by the fish based on the optimal foraging model. In the field, fish and invertebrates were collected with gill nets and hand nets respectively and the fish gut content was analyzed. In total, sixteen invertebrates’ taxa were collected from the two habitats. The proportion of the invertebrate’s overlaps from each of the habitat was calculated by Renkonen index and with Sorensen diversity index. Both indices showed a similarity larger than 65%, indicating that there was no significant difference in the invertebrates’ distribution in the P. australis and the Chara habitat. The fish caught with the gill nets were: roach (Rutilus rutilus), perch (Perca fluviatilis), tench (Tinca tinca), and rudd (Scardinius erythrophthalmus). The caught perch had eaten: Asellus aquaticus, Gammarus lacustris, Corixidae, and the larvae of Chironomidae and Zygoptera.A comparison was made on the invertebrates found in the field and the ones observed from the gut of the perch, and the findings were that the invertebrates that had more occurrence in the gut were less in proportion in the benthic samples. In the laboratory experiment perch ( Perca fluviatilis) was used as the predator fish and the prey organisms were Asellus aquaticus,Gammarus pulex, and Corixidae of three size categories. The results showed that perch handling time for A.aquaticus of the different size categories, was not significantly different (p>0.05); and the same results were valid for Corixidae and G. pulex. However, the intake rate of perch across the prey and their size categories were significantly different. The handling time was not significantly different which means that the predator fish will gain more in terms of intake rate as it prey on larger size prey items, thus harmonizing with the optimum foraging theory.MSc Ecology and Environmental Science