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1
Duna, Oliver Olwethu. "The influence of the physical environment, topography and time on the inshore distribution of invertebrate larvae : a multi-taxon approach." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017804.
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Coastal hydrodynamics regulate population dynamics through the distribution and dispersal of the meroplankton of many benthic invertebrates. I examined the hydrodynamics at four different sites on the south-east coast of South Africa and coupled them with larval sampling done at high temporal and spatial resolution. Day and night sampling was done at all four sites and a continuous 24 hour study was done in one site, both forms of sampling were carried out in autumn and spring. Samples were taken at two stations, 900 metres offshore and 300 metres apart, within each site. Water properties measured were depth, temperature and current velocity and direction. Plankton samples were collected using a plankton pump at various depths, from the surface, bottom and either side of the thermocline when present. A wide range of taxa (mostly bryozoans, bivalves, barnacles and decapods) was examined. 2-way ANOVAs were used to test the effects of time and depth on each taxon. In addition, multiple regression analyses were performed on each taxon to investigate the effects of hydrodynamics on the distribution of larvae. Bryozoanlarvae proved to be positively phototactic whilst bivalve veligers, barnacle larvae and decapod zoeae performed diel vertical migration. Turbulence and temperature had an effect on the vertical distribution/migration of decapod zoeae. These results highlight the role of taxon-specific responses to flow and the potential differential effects on larval retention and ultimately connectivity of benthic populations.
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Radabaugh, Kara. "Light-Environment Controls and Basal Resource Use of Planktonic and Benthic Primary Production." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4564.
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Consumers in marine and estuarine environments have a strong reliance on planktonic and benthic primary production. These two basal resources form the foundation of aquatic food webs, yet the abundance of phytoplankton and benthic algae are frequently inversely related due to competition for light and nutrients. As a result, optimal habitats for benthic and planktonic consumers vary spatially and temporally. To investigate these trends, three studies were conducted focusing on light attenuation and basal resources in a bay, river, and on a continental shelf.
δ13C and δ15N stable isotopes can be used as endogenous tracers to determine both the trophic level and basal resource use of consumers. δ13C values of primary producers are determined by the isotopic values of available CO2 and by the degree of photosynthetic fractionation (εp) that occurs during photosynthesis. εp by aquatic algae is greater in high CO2concentrations, high light, during slow growth rates, and for cells with a small surface area to volume ratio.
Interaction among these parameters complicates prediction of algal εp in a natural setting, prompting the investigation as to which factors would impact εp and δ13C in a dynamic estuary. Community-level fractionation of an assemblage of filamentous algae, pennate diatoms, and centric diatoms grown on glass plates was found to be positively correlated with photosynthetically active radiation (PAR), resulting in higher δ13C values for organic matter in low-light conditions. These results support the concept that the low-light benthic environment may contribute to the widely observed phenomenon of ~5 / higher δ13C values in benthic algae compared to phytoplankton.
Spatial and temporal variability in the isotopic baseline provides evidence of shifting biogeochemical controls on primary production. The West Florida Shelf in the eastern Gulf of Mexico transitions from a eutrophic ecosystem near the Mississippi River to an oligotrophic ecosystem in offshore continental shelf waters. Spatiotemporal variability in the δ13C and δ15N signatures of primary producers and fish populations were examined along this gradient. Muscle δ15N from three widely distributed fish species exhibited strong longitudinal isotopic gradients that coincided with the principal trophic gradient, whereas δ13C values of fish muscle and benthic algae were correlated with depth. The three fish species had relatively high site fidelity, as isotopic gradients were consistent between seasons and years. Isotopic mixing models showed all three fish species had a significant reliance on benthic algae as a basal resource.
Dynamic models of the West Florida Shelf isotopic baseline were created using spatial data and satellite-derived water quality characteristics as predictors. Models were constructed using data from three fish species and tested on four other species to determine if the models could be extrapolated to new taxa. Both dynamic and static δ15N models had similar predictive capabilities, indicating a fairly stable δ15N baseline. The satellite-derived dynamic variables explained more variation in baseline δ13C than static spatial descriptors.
Planktonic primary production can directly impact benthic food chains through phytoplankton deposition. A novel phytoplankton deposition detection method that combined water-column and benthic fluorometry with surficial sediment sampling was developed and assessed in a two-year study of the Caloosahatchee River estuary. Classifications based upon this detection method showed phytoplankton deposition dominated the upstream region and deposition was associated with reduced dissolved oxygen concentrations. Benthic algae dominated in downstream regions, particularly during low freshwater flow conditions when light absorption by colored dissolved organic matter was low.
This same Caloosahatchee River estuary study was used to determine if zooplankton aggregate in regions with optimal basal resource availability. The isopod Edotia triloba was found to associate with chlorophyll peaks when freshwater velocity was constant. Chlorophyll peaks were offset downstream or upstream from isopod aggregations when freshwater flow was accelerating or decelerating, implying that phytoplankton and isopods have different response times to changes in flow.
Temporal and spatial fluctuations in water quality and primary production introduce instability to aquatic consumers that primarily rely on one basal resource. The current global trends in eutrophication and increasing planktonic production are likely to be a liability for benthic consumers due to increased benthic hypoxia and light attenuation. The results of these studies indicate that both the location of consumers and their isotopic signatures can be impacted by factors, such as light attenuation, that control benthic and planktonic primary production.
3
Haverson, David Thomas. "Numerical modelling of the interaction between tidal stream turbines and the benthic environment." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/27784.
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The tidal stream industry has seen large growth in recent years, and the number of pre-commercial scale devices currently being tested reflects this development. However, commercialising this technology whilst showing that their environmental impacts is minimal remains a challenge. The impact on benthic communities is not considered to be a key strategic consenting issue, yet it is anticipated that the benthic habitat will change as a result of the presence of tidal turbines. To date, only single tidal turbine devices have been installed to demonstrate the application of tidal stream technology but despite successful tests there are still uncertainties surrounding the quantitative impacts these turbines have on local benthic communities. Unlike the wind industry, where physical effects of wind turbines have been catalogued through deployment of thousands of turbines, the tidal stream industry lacks these array scale quantitative data. Local impacts are known, but understanding the scale of the impacts and their relative significance of large arrays remains unknown. Tidal turbines (both single and arrays) interact with the hydrodynamics by decreasing the near field current flow directly in its wake through energy extraction and the drag caused by the physical structure. However, turbines may also affect the far field hydrodynamics, altering bed characteristics, sediment transport regimes and suspended sediment concentrations. As benthic habitats are closely linked to the physical seabed composition and the hydrodynamic conditions, the benthic environment is affected by to changes in the current flow. This thesis presents a series of studies investigating the interaction between tidal turbines and the benthic environment. Based on the hydrodynamic modelling software, TELEMAC2D, a numerical model has been developed to investigate the hydrodynamic impact of a single tidal array at Ramsey Sound, Pembrokeshire as well as the cumulative impact of multiple tidal developments in the Irish Sea. Based on the results of the models, the hydrodynamic outputs were used as inputs to drive a species distribution model, based on the software MaxEnt, to investigate how the distribution of benthic species altered in the presence of a 10MW tidal array at Ramsey Sound. Results of the study showed the development would have a minimal negative impact on the benthic environment.
4
Whomersley, Paul. "Uses of benthic ecology in the assessment of anthropogenic impacts in the marine environment." Thesis, Edinburgh Napier University, 2009. http://researchrepository.napier.ac.uk/Output/3741.
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The ability to detect and manage anthropogenic disturbances in the marine environment is more important than ever, given increasing pressure from a range of sources and the growing awareness of the sensitivity of some marine habitats. The main aims of this study were to ascertain if intensity and type of disturbance were important factors to consider during the assessment of these disturbances. Throughout, various techniques were used and assessed, e.g. primary, derived, multivariate and biological indices, as tools capable of indicating changes within benthic communities. A methodology of selecting appropriate indices linked to the perturbation of interest was also trialled. Finally, the behaviour of meiofauna and macrofauna towards in situ burial was investigated. The effects of disturbance were found to be type, as well as, site-dependent. In some cases, the intensity of disturbance was found to have non-linear effects. Site and disturbance-specific species and trophic group responses were also observed. The method used to select appropriate indices raised important questions. How can it be ensured that observed changes in indicator values are part of a cause-effect relationship? And, how do we identify / choose which of the potential impacts of the disturbance in question to use as a pressure indicator? Community-specific responses and sensitivities of meiofauna and macrofauna to the physical disturbance associated with in-situ burial highlight the importance of using both faunal types in the assessment of the effects of seabed disturbance in the marine environment. It is clear that no simple method exists for detecting disturbance which is applicable to all sites and situations. Hence, careful consideration, informed by ecological knowledge of sites and species, needs to be given to each case.
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Schuchert, Pia Christiane. "Modelling Large Scale Coral Reef Fish and Benthic Community Structures in a Subsistence Fishing Environment." Thesis, University of Newcastle upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519443.
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Dahl, Joakim. "Detection of human-induced stress in streams : comparison of bioassessment approaches using macroinvertebrates /." Uppsala : Dept. of Environmental Assessment, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s332.pdf.
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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.
8
Wai, Ho Yin. "Effects of deployment of artificial reefs on the marine benthic environment, with special reference to sediment physico-chemical characteristics /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-bch-b23750856f.pdf.
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Thesis (M.Phil.)--City University of Hong Kong, 2009.<br>"Submitted to Department of Biology and Chemistry in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references (leaves 144-191)
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Hansson, Mattias. "Macroinvertebrate sampling in hydropeaking rivers : Testing Hester-Dendy samplers in a laboratory environment using different flow conditions." Thesis, Karlstads universitet, Avdelningen för biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-78552.
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Degraded rivers and streams caused by disturbances have created a need for reliable tools to assess the ecological status of such ecosystems. Numerous methods and programs have been developed to assess ecological status using biological indicators, benthic macroinvertebrates are the most commonly used biotic indicator. The Hester-Dendy multi-plate sampler is a commonly used tool for sampling benthic macroinvertebrates, but its effectiveness under different environmental conditions has not been adequately tested. The aim of this study was to investigate if HD samplers assess the benthic macroinvertebrate community equally under different flow conditions. I investigated if the colonization of BMI in a constant flow differed from that of a variable flow (simulating a hydropeaking flow regime). This was studied using six aquariums, three as control with constant flows and three with variable flow conditions. One Hester-Dendy sampler and 50 benthic macro invertebrates from five different taxonomic orders were place in each aquarium. After five days of colonization the Hester-Dendy samplers were retrieved and benthic macroinvertebrates colonizing the Hester-Dendy samplers and still remaining in the aquariums were collected, preserved and analysed. Results showed that the mean sampling efficiency did not differ between the two treatments. On the other hand species diversity calculated from Shannon-Wiener index was significantly higher in the control treatment than in the variable flow treatment. The lower species diversity in the variable flow treatment is consistent with previous research on benthic macroinvertebrates affected by hydropeaking powerplants. These results can be seen as an indication of how a variable flow regime might affect the samples collected by HD samplers in a natural environment. As the artificial environments created are greatly different from a natural environment, this result might not therefore be representative in a natural environment.<br>Vattendrag kraftigt påverkade av antropogena störningarna har skapat ett behov av tillförlitliga verktyg för att kunna bedöma dessa vattendrags ekologiska status. Många olika metoder och program har utvecklats genom att använda olika biologiska indikatorer. Bentiska makroevertebrater är en av de vanligaste biotiska indikatorerna. En vanlig metod för att prov ta bentiska makroevertebrater är Hester-Dendy provtagaren. Syftet med denna studie var således att testa om provtagningseffektiviteten för Hester-Dendy provtagare påverkas olika av ett variabelt vattenflöde jämfört med ett jämnt vattenflöde. Detta studerades i sex akvarium, där tre akvarium agerade kontroll och utsattes för ett jämt flöde samt tre akvarium med variabelt flöde. En Hester-Dendy provtagare och 50 bentiska makroevertebrater från fem olika taxonomiska ordningar placerades i varje akvarium. Efter fem dagars koloniserings tid hämtades Hester-Dendy provtagarna och de bentiska makroevertebrater som koloniserade provtagaren såväl som akvariet bevarades i etanol och analyserades i labbet. Resultaten visade att den genomsnittliga provtagningseffektiviteten inte skilde sig åt mellan de två behandlingarna. Däremot var artdiversiteten beräknad med Shannon-Wiener-index signifikant högre i kontrollbehandlingen. Den lägre artdiversiteten i behandlingen med variabelt flöde stämmer överens med tidigare forskning om bentiska makroevertebrater påverkade av korttidsreglerande vattenkraftverk. Resultaten i denna studie bör ses som en indikation av hur ett varierande flöde kan påverka provtagnings effektiviteten hos en Hester-Dendy-provtagare. Detta med anledning av att den konstgjorda miljön som försöket utfördes i är vitt skilt från organismernas naturliga miljö vilket kan ha påverkat resultatet.
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Bergamino, Roman Leandro. "Spatial and temporal variations in trophic connectivity within an estuarine environment : benthic-pelagic and terrestrial-aquatic linkages via invertebrates and fishes." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017799.
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Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
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Brittle, Seth William. "Bioavailability and Transformation of Silver Nanoparticles in the Freshwater Environment." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1484594585990252.
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Camargo, Bruna Vielmo. "MACROINVERTEBRADOS DA LAVOURA DE ARROZ IRRIGADO TRATADA COM OS AGROTÓXICOS CARBOFURAN E PENOXSULAM." Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/5275.
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The rice cultivation (Oryza sativa) has been target of speculations because of its
effects in the environment. The intensive pesticides uses in the ricefields have
contributed in a meaningful manner to many things related to this crop. The purpose
of this study was to compare the benthic macroinvertebrates community in an
irrigated rice farm treated with pesticides Carbofuran (insecticide) and Penoxsulam
(herbicide) comparing to a control farm. The experiment was accomplished in an
experimental lowland area, from the Crop Science Departament of the Universidade
Federal de Santa Maria, during the harvest 2008/2009. To a benthic fauna sampling,
it was used a Corer sampler. It was accomplished five benthic macroinvertebrates
sampling during the study, the delimitation was in blocks divided, by chance, with
three repetitions, and the sampling happened in 3rd, 14th, 28th and 56th day after the
water entrance in the system. Besides, it was accomplished the following
determination: pH, temperature, dissolved oxygen and the pesticides persistence in
the water. The analysed pesticides, the Penoxsulam herbicide showed the biggest
water persistence, that was detected until the sampling day (56th day), without much
oscillation in its concentration according to the studied period. Among the sampling
organisms, Chironomidae was the dominant group in the three treatments. This way,
the total individuals abundance in this study was confirmed by this family organisms,
which didn t suffer a variation among the treatments during the sampling days (twoway-
ANOVA). The analyses variance, which evaluated the total macroinvertebrates
abundance and the taxon richness, detected interactions between the day sampling
factors and the (two-way- ANOVA) treatments. The posterior test (Tukey HSD)
showed the abundance in the community in the 8th day the sampling was different in
parcels treated with Penoxsulam and Carbofuran. However, on the other samplings,
the organisms total abundance was similar in the two treatments (Carbofuran,
Penoxsulam and Control). The posterior taxons richness comparison showed that
just in the 56th sampling day the macroinvertebrates richness in the controlled parcels
was superior than in the parcels treated with Carbofuran insecticide. The Diversity
Shannon level varied during the sampling days, but there wasn t a meaningful
difference in the (two-way-ANOVA) treatment. The results indicated that the
macroinvertebrates colonization process in the control areas didn t have a
meaningful variation related to the areas treated with Penoxsulam Carbofuran,
showing that the tested pesticides didn t affected the benthic fauna colonization, in
the ricefields. On the other hand, it was verified a subtle diversity along to the
successional process evaluated in this study (from the 3rd to the 56th day).<br>O cultivo de arroz (Oryza sativa) tem sido alvo de especulações devido aos efeitos deste
sobre o ambiente. A utilização intensiva de agrotóxicos em lavouras de arroz tem
contribuído de maneira significativa para as inúmeras questões que estão surgindo sobre
esta cultura. Dessa forma, o objetivo desse estudo foi comparar a estrutura da comunidade
de macroinvertebrados bentônicos em lavoura de arroz irrigado tratada com os agrotóxicos
Carbofuran (inseticida) e Penoxsulam (herbicida) em relação a uma lavoura controle. O
experimento foi desenvolvido na área experimental de várzea, do Departamento de
Fitotecnia da Universidade Federal de Santa Maria, durante a safra agrícola 2008/2009.
Para a amostragem da fauna bentônica, utilizou-se um amostrador tipo Corer. Realizaramse
cinco amostragens de macroinvertebrados bentônicos ao longo do estudo, sendo que o
delineamento foi de blocos ao acaso com três repetições, e as amostragens ocorreram no
3°, 14°,28° e 56° dia após a entrada de água no sistema. Além destes, foram realizadas as
seguintes determinações: pH, temperatura, oxigênio dissolvido e persistência dos
agroquímicos na água. Dos agrotóxicos analisados, o que apresentou maior persistência na
água foi o herbicida Penoxsulam, o qual foi detectado até o último dia de amostragem (56°
dia), sem muita oscilação em suas concentrações ao longo de todo o período de estudo.
Dentre os organismos amostrados, Chironomidae foi o grupo dominante nos três
tratamentos. Dessa forma, a abundância total de indivíduos deste estudo foi regida pela
abundância exclusiva de organismos desta família, a qual não variou entre os tratamentos,
ao longo dos dias de amostragem (ANOVA two-way). As análises de variância, que
avaliaram a abundância total de macroinvertebrados e a riqueza de táxons, detectaram
interações entre os fatores dias de amostragem e tratamentos (ANOVA two-way). O teste a
posteriori (Tukey HSD) mostrou que a abundância da comunidade no 8° dia de amostragem
diferiu entre as parcelas tratadas com Penoxsulam e Carbofuran. No entanto, nos demais
dias de amostragem, a abundância total de organismos foi similar entre todos os
tratamentos ( Carbofuran, Penoxsulam e Controle) Já a comparação a posteriori da riqueza
de táxons revelou que apenas no 56° dia amostral a riqueza de macroinvertebrados nas
parcelas controle foi superior a das parcelas tratadas com o inseticida Carbofuran. O Índice
de Diversidade de Shannon variou ao longo dos dias de amostragem, porém não houve
diferença significativa entre os tratamentos (ANOVA two-way). De uma forma geral, os
resultados indicam que o processo de colonização pelos macroinvertebrados nas áreas
controle não variou significativamente em relação as áreas tratadas com Penoxsulam
Carbofuran, demonstrando assim que os agrotóxicos testados não afetaram a colonização
da fauna bentônica, nas áreas de cultivo de arroz irrigado. No entanto, verificou-se um
aumento sutil da diversidade ao longo do processo sucessional avaliado neste estudo (do 3°
ao 56° dia).
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Bray, Laura. "Preparing for offshore renewable energy development in the Mediterranean." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/10099.
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The development of offshore wind farms and marine renewable energy devices in the Mediterranean is central to both national, and international, energy strategies for countries bordering the Mediterranean Sea. The ecological impacts of marine renewable energy development in the Mediterranean region, although essential for policy makers, are as yet unknown. The Northern Adriatic is identified as a plausible site for offshore wind farm development. Using the wider region (Adriatic and Northern Ionian) as a case study, this thesis examines the likely impact to the marine environment if an offshore wind farm is established. Site suitability, based on wind speed, bathymetry, and larvae connectivity levels are investigated along with the plausibility of the turbines operating as artificial reefs in the area. As offshore wind farms may alter the larval connectivity and supply dynamics of benthic populations, a connectivity map was constructed to identify areas of high and low connectivity in the Adriatic Sea. The Puglia coast of Italy is a likely larval sink, and displays some of the highest connectivity within the region, suggesting potential inputs of genetic materials from surrounding populations. Considering offshore wind farms could operate as artificial reefs, an in-situ pilot project was established to simulate the presence of wind turbines. Macroinvertebrates colonized the new substrata within the first few months but were lower in abundance when compared to a natural hard substrata environment. Time, turbine location, and the material used for turbine construction all affected the macro-invertebrate communities. In addition, fish abundances, and diversity were lower around the simulated OWF foundations in comparison to a natural hard substrata environment, and no increases in fish abundance occurred around the simulated turbines when compared to reference sites of soft substrata. This observation was validated with the use of an ecosystem modelling software (Ecopath with Ecosim), which simulated the overall ecosystem level impacts that would occur if 50 offshore monopile wind turbines were introduced to the Northern Ionian and colonized by macroinvertebrate communities. When compared to the baseline scenario (no simulated introduction of an OWF), the introduction of new habitat had no discernible impacts to the structure or functioning of the marine ecosystem. Noticeable changes to the ecosystem were only apparent if fishing restrictions were enforced in parallel with the simulated offshore wind farm; the ecosystem appears to become more structured by top down predation. In addition seabirds are also impacted by the reduction of fishing discards as a food source. These results are the first attempt to quantify the suspected benefits of offshore wind farms operating as de-facto marine protected areas.
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Freilich, Emily. "Restoration of Mauri (Life-Force) to Ōkahu Bay: Investigation of a Community Driven Restoration Process." Scholarship @ Claremont, 2018. https://scholarship.claremont.edu/pomona_theses/196.
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This thesis investigated the restoration of mauri (life-force) to Ōkahu Bay, Auckland New Zealand. Ōkahu Bay is part of the land and waters of Ngāti Whātua Ōrākei, a Māori hapū (sub-tribe). Ngāti Whātua Ōrākei has been driving the restoration, restoring Ōkahu Bay based on their worldview, visions, and concerns. This vision and control of the restoration process allows them to bring in the hapū in sustainable engagement and have the long-term vision and commitment necessary for self-determination. However, while there has been progress with projects and improved decision-making authority, hapū members are still not seeing their whānau (family) swimming in and caring for Ōkahu as much as they would like. Interviewees wanted to see an explicit focus on encouraging hapū members to use the bay, such as more educational programs and water-based activities, and continued efforts to improve water quality. Shellfish populations have also not recovered after a decade of monitoring due to structural aspects such as existing stormwater pipes. Changing these requires Auckland City Council to make stronger commitments to supporting Ngāti Whātua’s restoration. Overall, this investigation showed that in this restoration, a clean environment is essential to build community and a community is essential to build a clean environment. This community-driven restoration, while not perfect, has great potential to truly reconnect people with their environments, decolonize the land and the people, and create thriving ecosystems and people that benefit themselves, their communities, and the wider Auckland community.
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Helton, Rebekah R. "Ecology of benthic viruses in marine and estuarine environments." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 214 p, 2007. http://proquest.umi.com/pqdweb?did=1362525081&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Williams, Ryann A. "Comparing reef bioindicators on benthic environments off southeast Florida." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003191.
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Death, Russell G. "Environmental stability: Its effect on stream benthic communities." Thesis, University of Canterbury. Zoology, 1991. http://hdl.handle.net/10092/4812.
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The effects of environmental stability on benthic community structure were examined
at eleven sites (ten streams and a wind-swept lake shore) in the CassCraigieburn
region, New Zealand. Physicochemical conditions, apart from stability,
were similar at all sites. Epilithic biomass was considerably higher at the more
stable sites, but the composition of periphyton communities, and amounts of
benthic organic matter present were more strongly influenced by the nature of the
riparian vegetation than by stream stability.
Invertebrate species richness and density were markedly higher at the more
stable sites, but species evenness peaked at sites of intermediate stability. Sites of
high and low stability had species-abundance distributions that were modelled
best by the log series distribution, whereas sites of intermediate stability were
modelled best by the log normal distribution. Communities were dominated by a
common core of taxa at all sites, although their relative abundances changed
markedly between sites. Differences appeared to be related to a combination of
environmental stability and site location (e.g., in forest or grassland). Persistence
of the dominant taxa was high at all sites, but persistence of the entire fauna was
higher at the stable sites.
Communities at the more unstable sites appeared to be less complex and were
expected to have higher resilience (i.e., ability to recover from disturbances) than
those at more stable sites. Analysis of the local stability of community matrices indicated
that matrices were unstable at all sites, although those at the less stable
sites had eigenvalues closer to the stability criterion. These sites also had higher
theoretical resilience if eigenvalues beyond the 'criterion for stability were ignored.
An experimental study of recovery rates in four streams of different stability
did not provide any support for higher resilience at less stable sites, all communities
recovered at a similar rate. The composition of invertebrate communities at
several of the less stable sites could be attributed to simple random colonisation
processes; but community structure at the stable sites could not, although the
reason for this remains unclear.
Finally, food web structure was strongly influenced by environmental stability,
with shorter food chains, higher connectance and an overall more variable structure
in the less stable streams. This may be a direct response to stability per se or
mediated by it indirectly through its effect on the food base of the communities.
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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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Culhane, Fiona E. "The use of benthic communities in environmental health assessment." Thesis, Edinburgh Napier University, 2012. http://researchrepository.napier.ac.uk/Output/5687.
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Quality classification of water bodies commonly hinges upon the results of biotic indices. Biotic indices should reliably detect environmental change caused by anthropogenic stress; distinguish between different levels of disturbance; and be applicable in different areas. This study assesses current methods used in the assessment of benthic ecosystem health in transitional and coastal waters. Specifically, this study considers the performance of macrozoobenthos based biotic and diversity indices. Data utilised in the assessment covered a range of sites and environmental gradients including long term monitoring sites in Scotland; sites impacted by fish farms, organic waste discharge, and chemical effluent; estuarine sites; and sites from Galway Bay, Ireland, one of which was impacted by river discharge. Currently used indices of environmental status are based mainly on structural ecosystem properties and may not encompass all aspects of ecosystem health, such as functioning. Structural and functional based assessment methods were evaluated by comparing the performance of a range of standard benthic abundance indices and approaches focussing on intrinsic biological characteristics. Indices did not perform consistently in response to different types of impact – organic, chemical and physical, indicating some indices are unsuitable for the detection of multiple stressors. Index quality classifications agreed best in the most impacted sites but performed unpredictably in moderate conditions. Variability of indices increased as disturbance increased, decreasing the statistical certainty and confidence in the index values. Structural indices were found to be more variable than functional indices but the sensitivity of functional indices to anthropogenic disturbance needs further testing to determine whether they are able to detect low level disturbance. Functional indices may not be advantageous in regular monitoring over traditional methods but may provide a more informative assessment of ecosystem health. Use of biological traits may also give an indication of the type or cause of disturbance. Classification of moderate-good conditions using benthic indices is particularly ambiguous and distinguishing natural from anthropogenic disturbance remains one of the biggest challenges. The results indicate that complementarity of approaches is important in the assessment of quality of coastal and transitional benthic aquatic systems.
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Mednaoui, Hassan el. "Contribution à l'étude du comportement du cuivre en milieu marin côtier. : Aspects chimiques de la bioturbation de l'interface eau-sédiment par le gastéropode Hydrobia Ulvae." Pau, 1986. http://www.theses.fr/1986PAUU3002.
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Tinson, S. V. "The environmental metabolic function of benthic copepods from Esthwaite Water, Cumbria." Thesis, Lancaster University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373481.
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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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Sandin, Leonard. "Spatial and temporal variability of stream benthic macroinvertebrates : implications for environmental assessment /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-6056-5.pdf.
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Galanidi, Maria. "Spatial considerations and environmental constraints on benthic prey resources for common scoter." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443651.
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Mullen, Kortney. "Upstream Sources Inhibit Benthic Phosphorus Fluxes in the Lower Great Miami River, Southwest Ohio." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496852595092696.
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Hu, Irene Helen. "A novel trimodal sensor for eddy correlation measurements of benthic flux in aquatic environments." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121703.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 237-251).<br>Quantifying chemical fluxes between natural waters and their benthic sediments is a central problem in biogeochemistry, yet it is notoriously challenging. A relatively new method for measuring benthic fluxes, Eddy Correlation (EC) addresses many shortcomings of traditional techniques. Minimally invasive and measured in situ, EC is based on high-speed, simultaneous, and co-located velocity and concentration measurements. It has been successfully used in a range of settings to determine benthic fluxes of dissolved oxygen, using an Acoustic Doppler Velocimeter (ADV) to measure water velocity and an oxygen microelectrode to measure concentration. Widespread application to a larger range of compounds is limited, however, by the lack of chemical sensors that are fast, small, and sensitive enough for EC. To address this need, a novel trimodal sensor has been developed that is capable of high-speed, high-resolution measurements of fluorescence, temperature, and conductivity.<br>The core of the instrument is an optical fiber spectrofluorometer, which utilizes an LED for low-cost excitation; pair of 1000 [mu]m optical fibers for minimal disruption to velocity measurements; a tunable monochromator to enable a wide range of detection wavelengths; and a custom photon counting detector for maximum sensitivity. It can be used in an EC system to measure benthic fluxes of fluorescing compounds, such as fluorescent dissolved organic material. A fast thermistor and conductivity cell are also located at the tips of the optical fibers, enabling heat and salinity flux measurements that can be used as tracers for submarine groundwater discharge. Additionally, the ability to measure three simultaneous fluxes enables exploration of the potential to use the measured flux of one compound to infer another. Such 'flux tracing' would vastly expand the range of chemicals measurable with EC.<br>After development and testing of the individual sensors, the ability of the instrument to take three simultaneous, co-located measurements was demonstrated in a flume: under turbulent flow, the three sensors were able to detect similar features from an injection of warm, salty, fluorescent dye. The instrument was then coupled to an ADV for flux measurements, and tested in a specially constructed laboratory tank whereby benthic fluxes were released at known rates from the tank floor. The fluxes measured by all three sensors compared favorably with expected values. In addition, fluxes measured by the three sensors were observed to track each other, demonstrating the viability of flux tracing in settings with co-transported compounds.<br>by Irene Helen Hu.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Ellis, Joanne I. "Incorporation of spatial gradients into benthic impact assessment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0009/NQ34715.pdf.
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Polovodova, Irina [Verfasser]. "Benthic foraminifera and environmental change in the South-Western Baltic Sea / Irina Polovodova." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019552859/34.
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Da, Silva Ana Aranda. "Benthic protozoan community attributes in relation to environmental gradients in the Arabian Sea." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/18664/.
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“Live” (stained) and dead macrofaunal (>300 μm fraction) foraminifera in multicorer samples (0-1 cm and 0-5 cm layers) were analysed at six stations along a transect (100-3400 m water depth) across the Oman margin (Arabian Sea) oxygen minimum zone (OMZ). Very high abundances (2858 per 25.5 cm2), dominated by Uvigerina ex. gr. semiornata, were found in the upper 100 m. The 850 m site also had elevated abundances. These peaks probably represented upper and lower OMZ boundary edge effects, respectively. A total of 199 live species was recognized. Diversity was depressed between 100 m and 850 m and relatively higher at the 1250 m and 3400 m sites. Vertical distribution in the sediment reflected responses found across the horizontal gradient, with species concentrated in the top sediment where bottom-water oxygen concentration was low and distributed more evenly through the sediment where concentration was higher. In general foraminifera and metazoan responded similarly to oxygen and food availability, except that the lower boundary of edge effect was located at a shallower depth (700 m) for the metazoans. Live:dead ratios of foraminifera increased with water depth. The second part of the thesis concerns Gromia, a large marine protist with filose pseudopodia and an organic test that is abundant in the bathyal Arabian Sea. Deep-water Gromia-like morphospecies were discovered in the 1990’s but their relation to shallow-water species was not established. Little is known about gromiid diversity, reflecting the fact that these relatively featureless protists have few characters useful for species identification. Consequently, ultrastructural and molecular techniques were used to examine gromiid diversity on the Oman and Pakistan margins of the Arabian Sea (water depths 1000-2000 m). In total, 27 deep-sea gromiid sequences of the SSU rDNA gene and 6 sequences of the ITS rDNA region were obtained. The data confirmed that Gromia-like protists from the bathyal deep sea are related to shallow-water gromiids. Among Arabian Sea Gromia, seven lineages were identified based on molecular evidence. Five of them form a monophyletic group branching as a sister group to shallow-water species. Four lineages can be defined morphologically, while grape-like morphotypes include 3 lineages that cannot be distinguished morphologically. Each lineage probably represents a separate species, implying that deep-sea gromiid diversity is higher than indicated by their simple morphology. Morphological analysis adds 2 more species, giving a total of 9 deep-sea gromiid species, adding considerably to the number of known marine gromiids, only three of which are currently described.
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Sommer, Christian. "Processes and factors governing benthic community dynamics—environmental change in the Baltic Sea." Licentiate thesis, Södertörns högskola, Miljövetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-39750.
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As drivers of biogeochemical cycles and nutrient recycling, such as carbon turnover, the microbial community is essential in sustaining functioning ecosystems. Together with the metazoan community, the microbial community constitute the majority of all life in the benthos. Environmental change in biotic and abiotic factors may influence the dynamics of these communities, for example through a sorting or driving effect on the community structure through assembly processes. Environmental change, e.g. change in dissolved oxygen concentration, salinity and temperature, can directly or indirectly affect community composition. How, in what way, and to what extent, benthic bacterial and meiofaunal community composition in the eutrophied, brackish benthic environments, in the Baltic Sea sub-basin the Baltic Proper, respond to environmental change is understudied, both at local and seascape scale. This thesis aimed to study and understand the effects of environmental variation on the diversity and biogeographic patterns of Baltic Sea sediment bacterial and meiofaunal communities. A further aim was to understand the links between the different community levels by studying the interaction between meiofaunal- and macrofaunal communities in relation to environmental variation. Community diversity was analysed along a latitudinal transect of national environmental monitoring stations in the Baltic Proper using a framework of metapopulation and metacommunity theory. The analyses were based on environmental genomics, with high-throughput sequencing, bioinformatics and statistics. The total community genome was analysed using phylogenetic marker gene fragments as a proxy for taxonomic diversity, to investigate diversity, community structure and dynamics. Salinity and oxygen were found to be the main abiotic environmental drivers of benthic community composition and alpha- and beta-diversity patterns. Furthermore, macrofauna-meiofauna interactions were significantly more complex in higher salinity environments. Results also showed that both enhanced environmental gradients and dispersal following a major inflow of saline and oxygenated water from the Atlantic Ocean, influenced the composition of sediment bacterial communities at the seascape scale of the Baltic Sea, as shown by a reduced beta-diversity and increased alpha-diversity, and the development of a significant distance-decay of community similarity. This study also identified strong metapopulation dynamics of the benthic sediment bacterial communities with many satellite and a few core taxa. The outcomes from this study contribute to the understanding of how environmental variation and environmental change relate to changes in Baltic Sea benthic community diversity and composition, and important factors and processes governing community dynamics.
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Taormina, Bastien. "Potential impacts of submarine power cables from marine renewable energy projects on benthic communities A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions, in Renewable and Sustainable Energy Reviews 96, November 2018 Optimizing image-based protocol to monitor macroepibenthic communities colonizing artificial structures, in ICES Journal of marine science 77(2), March 2020." Thesis, Brest, 2019. http://theses-scd.univ-brest.fr/2019/These-2019-SML-Ecologie_marine-TAORMINA_Bastien.pdf.
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Dans un contexte de développement rapide des projets d’énergies marines renouvelables, le but de cette thèse était d’améliorer les connaissances sur les impacts potentiels des câbles électriques sous-marins sur les écosystèmes benthiques côtiers. En se focalisant sur la phase de fonctionnement, ce travail était essentiellement dédié à la caractérisation de l’effet récif généré par ces câbles et leurs structures associées (protection, stabilisation) sur les communautés épibenthiques fixées et la mégafaune mobile. L’étude était principalement basée sur l’utilisation d’images sous-marines (photo et vidéo) prises in situ par des plongeurs. Ce travail a mené à des réflexions méthodologiques sur la manière la plus efficace d’analyser ce genre de données afin d’appréhender pleinement la dynamique de colonisation des structures artificielles et leur rôle d’habitat pour des espèces commerciales. Outre cet effet récif, certains organismes se retrouvent exposés à des champs magnétiques émis par les câbles électriques. Ceci m’a conduit à mesurer expérimentalement l’impact de champs magnétiques artificiels sur le comportement du homard Européen (Homarus gammarus) au stade juvénile. Finalement, nous avons étudié in situ les potentiels bénéfices pour la macrofaune benthique de l’exclusion d’activités anthropiques autour de la route de câbles électriques. Le couplage d’approches in situ et ex situ m’a permis de mieux appréhender les impacts environnementaux associés aux câbles électriques sous-marins. Ces résultats permettront d’améliorer l’évaluation de l’empreinte écologique des futurs raccordements électriques<br>In a global context of rapid development of marine renewable energy projects, the aim of this PhD thesis was to better characterise the potential impacts of submarine power cables on coastal benthic ecosystems. The work specifically focused on the impacts associated with the operational phase. The major part of this work was dedicated to the reef effect created by these cables and their protective and stabilising structures on sessile epibenthic communities and mobile megafauna. This work was mainly based on underwater imagery, either video or photo collected in situ by divers. The challenge of working with underwater imagery has led me to optimise image analyses so as to effectively monitor benthic colonisation and to quantify artificial reef habitat provision to commercial species.In addition to this reef effect, colonising organisms are exposed to magnetic fields generated by the power cables. Thus, I designed an experimental study to assess the impact of realistic magnetic fields on the behaviour of juvenile European lobsters (Homarus gammarus). Finally, we explored the ecological impacts of excluding anthropogenic activity from the cables routes and potential benefits for benthic macrofauna. By coupling both in situ and ex situ approaches, my PhD research better characterises the environmental impacts associated with submarine power cables. These results will help to assess the ecological footprint of future power grid connections
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White, Carol Marie. "Organic matter cycling in hypoxic environments : the role of oxygen availability and benthic faunal communities." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15730/.
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Continental margins receive significant amounts of organic matter (OM) from terrestrial and marine sources, and it is estimated that over 80 % of all organic carbon (OC) preservation in marine sediments takes place in these areas. The least well understood aspect of OM cycling and burial in marine sediments is the role of benthic fauna living on and in the sediments. Seafloor communities influence marine sedimentary OM cycling and burial via a number of activities including digestion, bioturbation or burrowing, respiration, irrigation and ventilation, and through microbial stimulation. In turn, several factors are known to influence benthic biological processing of OM: oxygen, OM quality and quantity, temperature, and faunal size and abundance. Thus, dynamic relationships exist between benthic faunal communities, sediment geochemistry and oxygen availability, yet these remain poorly understood or quantified. Results from previous studies indicate that benthic communities usually intercept and rapidly ingest most of the OM flux delivered to the seafloor but that the response varies between faunal groups such as bacteria, foraminifera and megafauna. In this study, whole-community experiments were conducted at sites with a natural range of biogeochemical characteristics, across the Indian Margin oxygen minimum zone (Arabian Sea) and the Gotland Basin (Baltic Sea). In order to assess how short-term faunal OM processing varies with oxygen availability, shipboard incubation experiments were conducted under both ambient and manipulated oxygen concentrations. 13C and 15N-labelled phytodetritus (chlorella) was added to incubations to mimic seasonal OM fluxes. The added isotopically-labelled OM was traced into different pools including fractions of the faunal community, sediments, pore waters and overlying waters. Faunal uptake of added OM was determined by isotopic enrichment of organic carbon (δ13OC) and nitrogen (δ15Norg) of faunal body tissue, bacterial assimilation was assessed through 13C analysis of specific bacterial polar lipid fatty acids (PLFAs), and respiration was measured from 13C enrichment of dissolved inorganic carbon (DIC, ΣCO2). Results suggest that respiration is the dominant fate of OM at the seafloor in marine sediments. Organic matter processing is dominated by bacteria or foraminifera where oxygen is depleted and organic matter quality is low. Biological sedimentary organic matter processing is evenly shared between macrofauna, foraminifera and bacteria where oxygen is not limited and organic matter quality is high. This study is one of the first to conduct such isotope tracing experiments in conjunction with oxygen manipulation. Oxygen availability was found to be the over-riding control on organic matter preservation and short term cycling at the seafloor in both regions.
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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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Arshad, Aziz. "Temporal and spatial responses of benthic communities and populations across upper estuarine environmental gradients." Thesis, University of Plymouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284365.
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Stefanoudis, Paris V. "Benthic foraminiferal responses to mesoscale environmental heterogeneity at the Porcupine Abyssal Plain, NE Atlantic." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/403394/.
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Although our knowledge on the vast deep-sea biome has increased in recent decades, we still have a poor understanding of the processes regulating deep-sea diversity and assemblage composition, as well as their underlying natural variability in space and time. In the face of unprecedented anthropogenic impact on this environment, addressing this knowledge gap remains of paramount importance. In this thesis I focus on the effect of mesoscale (10s of kilometres) spatial heterogeneity, in the form of abyssal hills and surrounding abyssal plains, on benthic communities and specifically on foraminiferal faunas living at abyssal depths in the northeast Atlantic. ‘Live’ (Rose-Bengal-stained) and dead benthic foraminiferal assemblages, including rarely-studied soft-walled monothalamous species, were analysed based on a total of 16 Megacorer samples (0.25 cm2 surface area, 0-1 sediment horizon, >150 ?m sieve fraction) from five sites within the area of the Porcupine Abyssal Plain Sustained Observatory (PAP-SO, NE Atlantic, ~4850 m water depth). Three sites were located on the tops of small abyssal hills (~200-500 m elevation) and two on the adjacent abyssal plain. The main results of this analysis include the following. (1) Description of new morphotypes of poorly known primitive benthic foraminifera associated with (i.e. sessile on) planktonic foraminiferal shells and mineral grains. Some of these forms were more common on the hills, while others were more common on the plain. (2) Agglutinated foraminifera selected particles of different sizes on the hills compared to the plain, which affected their test morphometry and visual appearance. Distinct hydrodynamic conditions, and consequently distinct sediment granulometric characteristics between the two settings (hills, plain) resulted in foraminifera on the hills having more coarsely agglutinating tests. This information could be useful in palaeoecological interpretations of the fossil record. (3) Live benthic foraminiferal assemblages were significantly influenced by seafloor topography. Abyssal hills had a higher species density compared to the plain, supported a distinct fauna, and therefore tended to increase regional diversity. Enhanced bottom-water flow on hills, which affects organic matter supply and local sedimentology, were proposed to be responsible for these differences. (4) During the transition from live to dead benthic foraminiferal faunas there was a significant loss of delicate agglutinated and organic-walled forms. Unlike ‘live’ assemblages, the composition of the dead assemblages was very similar in hill and plain settings, suggesting that it would not be possible for paleoceanographers to differentiate between fossil foraminiferal faunas originating from these topographically contrasting settings. In conclusion, this study highlighted the significant effect of hills on agglutination patterns, assemblage composition and regional diversity of living benthic foraminifera. Since abyssal hills are one of the most common landforms on Earth, their presence may substantially enhance abyssal biodiversity, with important implications of deep-sea ecosystem functioning.
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Shah, Aliya. "Distribution of epifauna in offshore benthic environments along the west and south coast of South Africa." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29715.
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Marine unconsolidated sediments, such as sand, gravel and muds, constitute the most extensive benthic ecosystems globally. Biological data for these ecosystems are frequently sparse which can hinder the success and implementation of marine management strategies for benthic ecosystems. There are limited studies in South Africa on benthic epifauna. This study investigates the composition and distribution of epibenthic invertebrate assemblages along the west and south coast of South Africa (sampled using depth-stratified demersal trawls) to inform marine environmental management. Sample depth varied from 36m to 899m. Multivariate tools (PRIMER and PERMANOVA+) were used to analyse spatial (west vs south coast) and temporal (2011 vs 2017) patterns in epifauna. This study also investigated an overlap region between the west and south coast. A group average linkage cluster analysis defined biotopes using significant branching (p< 0.05). Biotopes were compared against the
2012 National Biodiversity Assessment (NBA) benthic habitat map to investigate
whether epifaunal biotopes identified, align with the existing classification. A significant
difference among epifauna between region and depth was found, where the west
coast had a higher average number of individuals and species per station.
Sympagarus dimorphus and Pelagia noctiluca were characteristic species for west
and south coast respectively. Epifauna was found to be significantly different between
2011 and 2017, with a notable increase in the abundance of Crossaster penicillatus in
2017. The majority of the biotopes aligned with the current NBA classification, in
particular the Agulhas Sandy Shelf Edge ecosystem type on the south coast and South
Atlantic Upper Bathyal and Namaqua Muddy Inner Shelf ecosystem types on the west
coast. This thesis contributes to the mapping and description of offshore ecosystem
types to inform marine environmental impact assessments, marine spatial planning
and marine protected area expansion.
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Dyson, Kirstie Elizabeth. "Biodiversity and ecosystem processes in heterogeneous environments /." St Andrews, 2008. http://hdl.handle.net/10023/698.
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Manley, Catherine Jane. "Environmental variables, including pollutants, affecting living benthonic Foraminiferida." Thesis, University of Plymouth, 1997. http://hdl.handle.net/10026.1/1706.
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Studies of living benthonic foraminiferal assemblages carried out by marine biologists are comparatively rare. This study of the changes in foraminiferal assemblages from three subtidal sites near Plymouth, U.K., has been carried out with the intention of determining the importance of various abiotic and biotic variables to the foraminiferal communities studied using statistical correlation. Temperature and salinity at depth and particle size characteristics together with organic content, bacterial abundance and type, and other meiofauna present were assessed monthly with samples taken for foraminiferal content, and for seasonal diatom analysis. Deformed specimens were very rare in the examined samples of natural assemblages. Three different systems were used in an attempt to culture Elphidium crispiim (Linne) for ecotoxicological studies, which failed. Ecotoxicological studies were carried out upon Roialieila elaticam Pawlowski & Lee and adult Ammonia batavits (Hofker). The types of deformation produced by laboratory-maintained Foraminiferida were found not to be specific to the stressor used and, therefore, the use of this group of Protozoa as indicators of specific pollution is not possible. The methods which Elphidium crispiim utilises to remain epifaunal were investigated and found to be primarily controlled by phototaxis, together with geotaxis.
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Cheng, Jie. "Paleoenvironmental Reconstruction of Florida Bay, South Florida, Using Benthic Foraminifera." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/179.
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Efforts that are underway to rehabilitate the Florida Bay ecosystem to a more natural state are best guided by a comprehensive understanding of the natural versus human-induced variability that has existed within the ecosystem. Benthic foraminifera, which are well-known paleoenvironmental indicators, were identified in 203 sediment samples from six sediment cores taken from Florida Bay, and analyzed to understand the environmental variability through anthropogenically unaltered and altered periods. In this research, taxa serving as indicators of (1) seagrass abundance (which is correlated with water quality), (2) salinity, and (3) general habitat change, were studied in detail over the past 120 years, and more generally over the past ~4000 years. Historical seagrass abundance was reconstructed with the proportions of species that prefer living attached to seagrass blades over other substrates. Historical salinity trends were determined by analyzing brackish versus marine faunas, which were defined based on species’ salinity preferences. Statistical methods including cluster analysis, discriminant analysis, analysis of variance and Fisher’s α were used to analyze trends in the data. The changes in seagrass abundance and salinity over the last ~120 years are attributed to anthropogenic activities such as construction of the Flagler Railroad from the mainland to the Florida Keys, the Tamiami Trail that stretches from the east to west coast, and canals and levees in south Florida, as well as natural events such as droughts and increased rainfall from hurricanes. Longer term changes (over ~4000 years) in seagrass abundance and salinity are mostly related to sea level changes. Since seawater entered the Florida Bay area around ~4000 years ago, only one probable sea level drop occurring around ~3000 years was identified.
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Braccia, Amy. "Quantifying the environmental factors that determine benthic macroinvertebrate assemblages in streams by analyzing stressors associated with a gradient of cattle grazing." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29326.
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Relationships between macroinvertebrate assemblages and environmental stressors were assessed from fall 2002 through spring 2004 in five small streams that represented a study design that involved a gradient of increasing stress (increased cattle density). Macroinvertebrate assemblages were related to environmental factors that were quantified at the sample scale. Environmental factors and macroinvertebrates were concurrently collected so that assemblage structure could be directly related to environmental variables and so that the relative importance of stressors associated with cattle grazing in structuring assemblages could be assessed. Macroinvertebrate metrics showed significant and strong responses to cattle density during most sampling periods. The majority of metrics responded negatively to the grazing gradient, while a few (total taxa richness, number of sensitive taxa, and % collector filterers) increased along the gradient before declining at the most heavily grazed sites. Total number of sensitive taxa and % Coleoptera had the strongest relationship with cattle density throughout the study period. Based on sample-scale, quantitative measures of environmental variables, measures of physical habitat (% fines and substrate homogeneity) were most important in structuring assemblages. Detrital food variables (coarse benthic and fine benthic organic matter) were secondarily important while autochthonous food variables (chlorophyll a and epilithic biomass) were not as important in influencing assemblage structure. Based on a comparative analysis of reach-scale habitat measures and estimates, quantitative measures of % fines, collected from within an enclosed sampler concurrently with macroinvertebrates, were the best predictor of macroinvertebrate assemblages. Quantitative measures and visual estimates of riparian and channel characteristics had strong relationships with macroinvertebrate metrics but the relationships were never as strong as those detected with instream measurements of % fines. The channel characteristic, bank height, was the best predictor of % fines.<br>Ph. D.
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Willey, Katherine Tara. "Environmental Factors Determining the Pre-Restoration Benthic Macroinvertebrate Assemblage In A Stream Used By Cattle." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35221.
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I investigated the baseline benthic macroinvertebrate community in relation to the environmental conditions in a section of Smith Creek, north of Harrisonburg, VA, prior to restoration. Quantitative benthic macroinvertebrate and environmental samples were collected in April and September 2006 from the Bruce Farm (BR) section of Smith Creek and the nearby Mixed Use (MU) section of Mountain Run. BR had been heavily used for cattle grazing for decades and suffered from sediment, nutrients, and lack of a forested riparian zone. MU had a forested riparian zone, but still received nutrient and sediment inputs from upstream cattle grazing. Visual habitat assessments were performed in September 2006 and were compared to quantitative measures. Benthic macroinvertebrate densities and taxa richness were greater at BR (total density for combined seasons = 52,438; taxa richness for both seasons = 84) than MU (total density for combined seasons = 3,982 and taxa richness for both seasons = 63). Biological environmental variables related to nutrients and growth of plants on rocks (ash-free dry mass, chlorophyll a, epilithic biomass) influenced the benthic macroinvertebrate assemblage more than physical environmental variables related to the substrate composition (% fines, % gravel, Traskâ s sorting coefficient). Visual habitat estimates were not as effective as quantitative measures of habitat for explaining the benthic macroinvertebrate assemblage.<br>Master of Science
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Olson, John R. "The Influence of Geology and Other Environmental Factors on Stream Water Chemistry and Benthic Invertebrate Assemblages." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1327.
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Catchment geology is known to influence water chemistry, which can significantly affect both species composition and ecosystem processes in streams. However, current predictions of how stream water chemistry varies with geology are limited in both scope and precision, and we have not adequately tested the specific mechanisms by which water chemistry influences stream biota. My dissertation research goals were to (1) develop empirical models to predict natural base-flow water chemistry from catchment geology and other environmental factors, (2) extend these predictions to nutrients to establish more realistic criteria for evaluating water quality, and (3) test the hypothesis that catchment geology significantly influences the composition of stream invertebrate assemblages by restricting weak osmoregulators from streams with low total dissolved solids (TDS). To meet goal 1, I first mapped geologic chemical and physical influences by associating rock properties with geologic map units. I then used these maps and other environmental factors as predictors of electrical conductivity (EC, a measure of TDS), acid neutralization capacity, and calcium, magnesium, and sulfate concentrations. The models explained 58 – 92% of the variance in these five constituents. Rock chemistry was the best predictor of stream water chemistry, followed by temperature, precipitation and other factors. To meet goal 2, I developed empirical models predicting naturally occurring stream total nitrogen and total phosphorus concentrations. These models explained most of the spatial variation among sites in total nitrogen and phosphorus and produced better predictions than previous models. By determining upper prediction limits that incorporated model error, I demonstrated how predictions of nutrient concentrations could be used to set site-specific nutrient criteria and accounted for natural variation among sites better than regional criteria. To meet goal 3, I experimentally manipulated (high and low) EC in both stream-side and laboratory flowthrough microcosms and measured survival, growth, and emergence of 19 invertebrate taxa. Observed variation among taxa in survival between treatments predicted taxon EC optima estimated from field observations (r² = 0.60). Taxa with the greatest differences in survival between treatments also had the highest EC optima, indicating that the inability to persist in low EC likely restricts the distributions of some taxa.
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Beltran, Makenzi. "Measuring Nitrogen Transformation in Wastewater Impacted Streams Using In-Situ Benthic Chambers." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7437.
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Acrylic chambers and metal frames were installed at the sediment-water interface of streams impacted by the effluent from wastewater reclamation facilities in order to determine nitrogen rates for nitrification, denitrification, assimilation, ANAMMOX, and DNRA. Each chamber was dosed with an isotopic form of nitrate (15NO3 - ), and both isotopic (15N) and non-isotopic (14N) samples were collected. The project locations included East Canyon Creek near the East Canyon Wastewater Reclamation Facility in Park City, Utah and Box Elder Creek near the Brigham City Wastewater Treatment Plant in Brigham City, Utah. Separate chamber measurements were conducted upstream and downstream of each wastewater reclamation facility in order to determine the impact of the wastewater effluent on the stream. At the conclusion of the study, significant rates for both traditional (nitrification, denitrification, assimilation) and non-traditional nitrogen transformations (DNRA, ANAMMOX) were found at various locations. Specific transformations were found exclusively upstream or exclusively downstream of the wastewater treatment plant. Transformations that were found both upstream and downstream of the treatment plants were not significantly different, indicating no impact from the WWTPs on nitrogen transformations. Additionally, the use of isotopic nitrogen for the study did not prove necessary for determining nitrification and denitrification rates.
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Greenberg, Marc Samuel. "Defining Benthic Organism Exposure: Bioavailability and Effects of Non-Polar Organics." Wright State University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=wright1074096654.
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McElroy, Anne Elizabeth. "Benz(a)anthracene in benthic marine environments : bioavailability, metabolism, and physiological effects on the polychaete Nereis virens /." Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1985. http://hdl.handle.net/1912/3134.
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Dunn, Joseph G. "Comparative analysis of the benthic infauna and sediment for two small estuaries in Connecticut /." Click for abstract, 1998. http://library.ctstateu.edu/ccsu%5Ftheses/1488.html.
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Thesis (M.S.)--Central Connecticut State University, 1998.<br>Thesis advisor: Dr. Clayton Penniman. " ... in partial fulfillment of the requirements for the degree of Master of Science in Biology." Includes bibliographical references (leaves 59-63).
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Long, William Christopher. "Hypoxia and Macoma balthica : ecological effects on a key infaunal benthic species /." W&M ScholarWorks, 2007. http://www.vims.edu/library/Theses/Long07.pdf.
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Grannis, Betsy M. "Impacts of Mobile Fishing Gear and a Buried Fiber-Optic Cable on Soft-Sediment Benthic Community Structure." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/GrannisBM2005.pdf.
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Fajemila, Olugbenga Temitope [Verfasser]. "Benthic Foraminifera Assemblages from Shallow-Water Ecosystems: Implications for Environmental Assessment and Monitoring / Olugbenga Temitope Fajemila." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1154485854/34.
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Chiziane, Hércio Issac Patrício. "Analysis of morphometric attributes of benthic nematodes as descriptors of the different ecological conditions." Master's thesis, ISA/UL, 2018. http://hdl.handle.net/10400.5/17979.
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Mestrado em Gestão e Conservação dos Recursos Naturais - Instituto Superior de Agronomia / Universidade de Évora<br>Free-living nematodes have been and are continually considered excellent bioindicators by several authors. Their high structural and functional diversity makes them more diversified and numerically dominant in aquatic habitats, with a wide distribution ranging from untouched habitats to highly polluted habitats. This fact as called the attention of many researchers who in turn motivated and promoted their use in the evaluation of the quality of water bodies. Farther, studies showed that morphometry and biomass are two important aspects to consider in ecological studies of free-living nematodes. The current study focuses on the investigation of the morphometric attributes of the free-living nematodes of the Tagus estuary (Portugal) in order to relate them to the various environmental conditions of the sediment along the estuary. Therefore, the following null hypothesis was tested: There will be no differences in the nematode morphometric parameters (length, width, L / W ratio and biomass) in the different sections of the estuary. Conclusions led to the rejection of the null hypothesis as significant differences were observed along the sections of the estuary for most of the morphometric attributes measurements taking in consideration the six most abundant genera of nematodes in the Tagus estuary (Terschellingia, Sabatieria, Daptonema, Ptycholaimellus, Viscosia and Anoplostoma). Though salinity, depth, grain size variables and organic matter were the environmental variables that were found to be more correlated with the nematode morphometric attributes variance along the estuary, nematode size and shape at investigated sections most likely reflected differences in quality and quantity of organic material and sediment size of the estuary. Most of the variability in terms of nematode morphometry along the Tagus estuary were verified for the genera Terschellingia leading to the conclusion that this genera can provide better information about the different environmental conditions of the sediment along the Tagus estuary<br>Os nemátodes de vida livre foram e são continuamente considerados ótimos bioindicadores por vários autores. A elevada diversidade estrutural e funcional dos nemátodes de vida livre torna-os o grupo mais diversificado e numericamente dominante em habitats aquáticos, com uma ampla distribuição que varia de habitats intocados a habitats altamente poluídos. Este fato chamou a atenção de muitos investigadores que, por sua vez, motivaram e promoveram o seu uso na avaliação da qualidade das massas de água. Além disso, estudos mostraram que a morfometria e biomassa são dois aspectos importantes a serem considerados em estudos ecológicos de nemátodes de vida livre. O corrente estudo foca-se na investigação dos atributos morfométricos dos nemátodes de vida livre do estuário do Tejo de modo a relacioná-los com as várias condições ambientais do sedimento ao longo do estuário. Para este efeito foi testada a seguinte hipótese nula: Não haverá diferenças nos parâmetros de nemátodes (comprimento, largura, relação C/L e biomassa) em diferentes secções do estuário. As conclusões levaram à rejeição da hipótese nula. Diferenças significativas foram observadas ao longo das seções do estuário para a maioria das medições dos atributos morfométricos dos seis géneros mais abundantes de nemátodes no estuário do Tejo (Terschellingia, Sabatieria, Daptonema, Ptycholaimellus, Viscosia e Anoplostoma). Embora a salinidade, profundidade, tamanho do sedimento e matéria orgânica tenham sido as variáveis ambientais mais correlacionadas com a variância dos atributos morfométricos dos nemátodes ao longo do estuário, o tamanho e a morfologia de nemátodes nas seções investigadas refletiram diferenças na qualidade e quantidade de matéria orgânica e tamanho do sedimento do estuário. A maior parte da variabilidade em termos de morfometria dos nemátodos ao longo do estuário do Tejo foi verificada para o género Terschellingia, levando à conclusão de que este género pode fornecer uma melhor informação sobre as diferentes condições ambientais do sedimento ao longo do estuário do Tejo<br>N/A