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Lacey, Jack H. "Late Quaternary palaeoenvironmental reconstruction from Lake Ohrid." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31993/.
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Lake Ohrid is a large, deep, ancient lake located on the Balkan Peninsula and has an extraordinary degree of endemic biodiversity. A deep drilling campaign was carried out in 2013 as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project to better understand the influence of climate and environmental change on evolutionary patterns and endemism. Initial results from a 569 m sediment succession drilled in the centre of the basin indicate continuous lacustrine conditions over the past ca. 1.2 Ma. This thesis presents new stable isotope data from carbonate within the upper 248 m of the composite profile, covering the last ca. 640 ka at a millennial-scale resolution (≈ 0.5 ka). Isotope data are used to provide a long-term palaeoenvironmental reconstruction, which is supported by a quantitative model of modern lake water isotope composition and a detailed multi-proxy investigation of climate evolution since the last glacial period. Water balance calculations confirm Ohrid to be an evaporative system with a complex hydrology. Variations in the isotope composition of modern lake water are suggested to represent long-term fluctuations in water balance. A trend from wetter to drier conditions through the Holocene is consistent with regional and hemispheric processes related to changes in insolation. Over the last ca. 640 ka, endogenic calcite is precipitated in abundance during warm stages, however carbonate is negligible during glacial periods with the exception of discrete horizons comprising early diagenetic authigenic siderite. The oxygen isotope composition of lake water, calculated using calcite and siderite, indicates more evaporated conditions during warm stages and fresher lake water in glacial phases. Low frequency variability shown by calcite isotope data suggests relatively stable conditions before ca. 450 ka, a transition to a wetter climate between ca. 400-250 ka, and a trend to drier climate conditions after ca. 250 ka. Higher frequency millennial-scale oscillations and abrupt climate events observed during warm stages are likely associated with regional climate change as a function of orbital forcing. This study emphasises the potential of Lake Ohrid as a valuable archive of climate change in the central Mediterranean region and demonstrates the efficacy of isotope data for palaeoenvironmental reconstruction at Lake Ohrid.
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Wood, Roland Neville. "Ecology of Lake District Ostracoda." Thesis, University of Greenwich, 1992. http://gala.gre.ac.uk/6348/.
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Freshwater ostracods are potentially useful for environmental monitoring and, since their calcified valves may be preserved in lake sediments, are also valuable in palaeolimnological studies of environmental pollution such as eutrophication and surface water acidification. To establish a data-base of ostracod ecology, biannual survey work in 1989-1990 was performed in 75 lakes and tarns of a wide range of physico-chemical characteristics in the Lake District in Cumbria, ranging from large eutrophic lakes such as Windermere and Ullswater to tiny, upland acidic tarns. pH ranged from 4.3 (Black Pool) to 8.0 (Browns Tarn). Littoral margin samples were taken from all 75 sites and yielded 31 ostracod species, of which 8 were new to the Lake District fauna. The collection of multiple littoral samples from two sites demonstrated that a single sample produced an adequate faunal representation if it encompassed a variety of microhabitats. Statistical analysis, incorporating a multistage, multivariate technique, has shown that 18 species make up over 99% of the data set, and that 5 species, Cvpria ophthalmica, Cvclocypris ovum. Metacvpris cordata. Candona Candida and Cvpridopsis vidua. dominate the community in 71% of the sites containing ostracods, forming eight distinct assemblage groups. No ostracods were found in 13 of the 75 sites, 11 of which were acidic, having a pH of below 5.7. Equations were derived to predict both species distribution and diversity. Important predictors of community structures were shown to be pH, [Ca] 2+ , [Mg] 2+ , substrate, lake size and altitude. The equations were tested by further sampling of additional sites in the Lake District. Predictions of total species number and density generally provided an excellent fit to the observed data, although individual species predictions were poorer, especially in alkaline conditions. Substrate was not included in the analysis, due to quantitative difficulties, but this factor must be included in future predictive models as it was shown to be an important parameter in determining distribution. Deep-water sampling was carried out in 6 lakes. 10 species were collected, including Candona necrlecta, which was absent in the littoral samples. 9 species contributed to over 99% of the data set, and 2, Cypria ophthalmica and Candona Candida dominated the community in 75% of the sites containing ostracods. Community structure was predominantly determined by water depth (together with the associated temperature effect) and substrate. The sex ratio of Cyclocvpris ovum was shown be biased towards the female only at high alkalinities. Other species had sex ratios biased towards the male or female, the values independent of water quality. Large, swimming ostracod species were absent in sites containing fish. A series of laboratory experiments using three species of Ostracoda, (Cvpria ophthalmica. Cvpricercus fuscatus. and Eucvpris virens), and a predator (Gasterosteus aculeatus) correlated increasing ostracod size with an increased rate of predation, suggesting that predation could limit ostracod distribution. From the results of principal component analysis, it was concluded that the main characteristics that chemically differentiate the sites are calcium, magnesium, hydrogen and sodium ion concentrations. Toxicity tests were used to expose selected species to a wide range of calcium, magnesium, sodium and aluminium concentrations, at both neutral and acidic pH levels. Aluminium was selected as it has been highlighted as a major factor in the toxicity of acid waters. All species tolerated a wider spectrum of ionic concentrations than those in which they were recorded in the field, although the order of species survival in the experiments was similar to that found in the Lake District. It is suggested that whilst adult Ostracoda do not suffer from the acute toxicity of pH or aluminium, they may be unable to successfully reproduce in harsh environmental conditions. The waters of the English Lake District are not particularly species-rich due primarily to low alkalinity and low levels of dissolved cations, but also because they are cold. Only in small, ion-enriched pools is ostracod density sufficiently high to warrant their consideration as important detritivorous contributors in the cycling of nutrients. The Lake District fauna is compared with those recorded in other parts of Britain and Europe.
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Hunter, Peter D. "Remote sensing in shallow lake ecology." Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/365.
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Shallow lakes are an important ecological and socio-economic resource. However, the impact of human pressures, both at the lake and catchment scale, has precipitated a decline in the ecological status of many shallow lakes, both in the UK, and throughout Europe. There is now, as direct consequence, unprecedented interest in the assessment and monitoring of ecological status and trajectory in shallow lakes, not least in response to the European Union Water Framework Directive (2000/60/EC). In this context, the spatially-resolving and panoramic data provided by remote sensing platforms may be of immense value in the construction of effective and efficient strategies for the assessment and monitoring of ecological status in shallow lakes and, moreover, in providing new, spatially-explicit, insights into the function of these ecosystems and how they respond to change. This thesis examined the use of remote sensing data for the assessment of (i) phytoplankton abundance and species composition and (ii) aquatic vegetation distribution and ecophysiological status in shallow lakes with a view to establishing the credence of such an approach and its value in limnological research and monitoring activities. High resolution in-situ and airborne remote sensing data was collected during a 2-year sampling campaign in the shallow lakes of the Norfolk Broads. It was demonstrated that semi-empirical algorithms could be formulated and used to provide accurate and robust estimations of the concentration of chlorophyll-a, even in these optically-complex waters. It was further shown that it was possible to differentiate and quantify the abundance of cyanobacteria using the biomarker pigment C-phycocyanin. The subsequent calibration of the imagery obtained from the airborne reconnaissance missions permitted the construction of diurnal and seasonal regional-scale time-series of phytoplankton dynamics in the Norfolk Broads. This approach was able to deliver unique spatial insights into the migratory behaviour of a potentially-toxic cyanobacterial bloom. It was further shown that remote sensing can be used to map the distribution of aquatic plants in shallow lakes, importantly including the extent of submerged vegetation, which is central to the assessment of ecological status. This research theme was subsequently extended in an exploration of the use of remote sensing for assessing the ecophysiological response of wetland plants to nutrient enrichment. It was shown that remote sensing metrics could be constructed for the quantification of plant vigour. The extrapolation of these techniques enabled spatial heterogeneity in the ecophysiological response of Phragmites australis to lake nutrient enrichment to be characterised and assisted the formulation of a mechanistic explanation for the variation in reedswamp performance in these shallow lakes. It is therefore argued that the spatially synoptic data provided by remote sensing has much to offer the assessment, monitoring and policing of ecological status in shallow lakes and, in particular, for facilitating the development of pan-European scale lake surveillance capabilities for the Water Framework Directive (2000/60/EC). It is also suggested that remote sensing can make a valuable contribution to furthering ecological understanding and, most significantly, in enabling ecosystem processes and functions to be examined at the lake-scale.
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McKinnon-Newton, Laurie. "Ecology of plankton in a terminal lake Walker Lake, Nevada, USA /." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446303.
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Wood, Hannah. "The benthic ecology and food web dynamics of Te Waihora (Lake Ellesmere)." Thesis, University of Canterbury. School of Biological Sciences, 2008. http://hdl.handle.net/10092/2274.
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Coastal and shallow lakes are often subjected to eutrophication due to nutrients from catchment farming activities. Lake Ellesmere (Te Waihora) is a hyper-eutrophic lake which has gained recent attention because of concerns over its ecological health and fishery status. This study investigated the benthic ecology of the lake by extensive spatial and temporal sampling. Eight littoral sites were sampled on a single occasion, and 20 benthic sites were sampled once per season for one year. Water chemistry conditions, substrate and invertebrate communities varied significantly around the lake. Salinity, pH, DO and seston were primarily affected by freshwater inputs from inflow streams and salt water intrusion due to the lake opening to the sea. On these occasions, salinity reached 32 ‰ at the lake outlet. The lake invertebrate community was depauperate, comprising of only two species of invertebrate predators restricted to the littoral zone and eight benthic invertebrate taxa, dominated by oligochaetes, amphipods and chironomids. Benthic invertebrate abundances also reflect the dominant local substrate, where oligochaetes and chironomids preferred areas of silt substrate, whereas Potamopyrgus preferred harder substrate. Stable isotope and gut analysis determined that the primary food sources within the lake were phytoplankton and algae. Macrophytes provided a minimal contribution to the food web, possibly relating to the change in status from a clear water, macrophyte dominated lake to a turbid, phytoplankton dominated condition since the Wahine Storm in 1968. Isotope analysis also showed that the lake food web was markedly different in its carbon values from food webs of its inflow streams and nearby marine source. However the lake food web did show a marine-derived carbon signature. A mesocosm experiment testing the effect of common lentic predators on the abundance of the lake chironomid Chironomus zealandicus, showed that if invertebrate predators were present in the lake they could markedly reduce the abundance of the pest prey species. This study highlights that the frequent re-suspension of bottom sediments, lake level fluctuation resulting in wetting and drying of littoral zones, and the management of the lake opening to the sea all have an effect on the benthic ecology of Te Waihora.
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Snell, Margaret Anderson. "Employing Institutional Economics to Explain the Distribution and Success of Maine Lake Associations." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/SnellMA2009.pdf.
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Frost, Jessica Rene. "Ecology of Lake Griffin, a hypereutrophic cyanobacteria-dominated lake in Central Florida." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000959.
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Scheuerell, Mark David. "Environmental drivers of spatial and temporal variability in lakes /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5144.
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Eaton, Dewey Mitchell 1960. "Ecology of arctic grayling in Becharof Lake tributaries." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/291517.
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I studied the grayling populations in 4 tributaries of Becharof Lake. The grayling in Ruth River, and Salmon, Featherly and Becharof Creeks appear to be independent populations, with high fidelity to specific streams. All populations overwintered in the lake and migrated into the streams when water temperatures reached about 2.5 C. These populations contained some of the largest grayling in the state; generally >50% of the population exceeding 6 years in age and had fork lengths >400 mm. Interstream movement rates were about 2%, but intrastream movement was higher (18%). Spring migration into the streams extended from May-July. This extended migration may have invalidated the assumption of a closed population, and resulted in higher than actual estimated abundance. Abundance ranged from a low of 33 grayling/Km in Featherly Creek to a high of 230 grayling/Km in Becharof Creek. Survival rates were similar in all streams.
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Nordström, Emil. "Effects of Salinization on Lake Metabolism." Thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79006.
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With rising salinity levels in many freshwaters across the globe caused by for example sealevel rise and de-icing salts, it becomes important to understand what effect it has on freshwater ecosystems, since the lakes and rivers themselves are important parts in the global carbon cycle. In this study I have looked at what effects increased salinity levels have on different lakes metabolism, specifically oxygen concentration and primary production. The experiment was conducted using mesocosms in three different lakes in Sweden, separated both geographically and by nutrient status (eutrophic, oligotrophic, and dystrophic as well as oligotrophic). The response to increased salinity differed between the lakes; the increased salinity had a strong negative effect on the oligotrophic lake. In general, increased salinity caused a decline in oxygen content, both the maximum value and the amount of diurnal variation, as well as primary production. Therefore, the conclusion is that a rise in salinity will affect lake metabolism in a detrimental way, with a stronger effect on more sensitive lakes.Med stigande saltnivåer i många sötvatten världen över, orsakade av exempelvis ökande havsnivåer och applicering av vägsalt, blir det viktigt att förstå vilken påverkan detta har på ekosystem i sötvatten då de utgör en viktig del I den globala kolcykeln. I den här studien har jag tittat på vilken effekt förhöjda salthalter har på olika sjöars metabolism, specifikt syrehalt och primärproduktion. Experimentet utfördes med hjälp av mesokosmer i tre olika svenska sjöar, skilda både geografiskt och trofiskt (eutrof, oligotrof samt dystrof och oligotrof). Sjöarnas respons till den ökade salthalten varierade; saltet hade en starkt negativ effekt på den oligotrofa sjön. På en generell nivå så sjönk syrehalten, både maximum värden och dygnsvariationen, samt primärproduktionen vid högre salthalter. Slutsatsen blir därför att ökade saltnivåer kommer att påverka sjöars metabolism negativt, med en starkare effekt på mer känsliga sjöar.
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Clasen, Jessica Liz. "Viral ecology of lakes : a descriptive and ecological study of viruses that infect phytoplankton." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/909.
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Since the 'discovery' of the high abundance of viruses in aquatic environments, it has been generally assumed that viruses in lakes are similar to those in oceans. I directly compared these two systems using a large, robust data set. Viral abundance was significantly different among the surveyed environments. The relationship between viral and bacterial abundance indicated a fundamental difference between lakes and oceans, and suggested that viruses infecting phytoplankton may be more important in lakes.
Molecular techniques (PCR & DGGE) were used to document spatial and temporal variations in the richness of viruses that infect eukaryotic phytoplankton (Phycodnaviridae) in lakes at the Experimental Lakes Area (ELA). Phycodnavirus richness was highest in the eutrophic lake, and during the spring/early summer in all the lakes. Viral richness was closely associated with phytoplankton abundance and composition. As a result, richness was influenced by trophic status, while patterns of richness were affected by regional climatic conditions.
Phylogenetic analysis of environmental Phycodnavirus DNA polymerase (pol) sequences indicated that freshwater Phycodnaviruses are genetically different from cultured isolates and marine environmental sequences. A genetic distance analysis indicated that polsequences > 7 % different infected different host species. Therefore, the 20 different freshwater sequences likely infected nine different hosts. Multivariate statistics identified seven possible phytoplankton hosts, including chlorophytes, chrysophytes, diatoms and dinoflagellates.
Finally, the modified dilution experiment was evaluated as an approach for estimating viral-mediated phytoplankton mortality in two lakes at the ELA. Experiments resulted in non-significant apparent growth rate regressions. While a model analysis, indicated that the method was sensitive to poorly constrained parameters such as burst size and length of the lytic cycle, making it unsuitable for estimating mortality rates in these lakes.
These studies indicate that Phycodnaviridae are a genetically rich and dynamic component of lakes. Their richness is influenced by both the chemical and physical components of their environment. Although the presence of these viruses indicates that they are a source of phytoplankton mortality, the magnitude of their impact on structuring phytoplankton communities awaits methodological advances. Nonetheless, these findings support the view that viruses infecting phytoplankton are ecologically important componentsof lake ecosystems.
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Mannini, Piero. "Ecology of the pelagic fish resources of Lake Tanganyika." Thesis, University of Hull, 1998. http://hydra.hull.ac.uk/resources/hull:5722.
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Most of the scientific knowledge on the pelagic fish (the clupeids Stolothrissa tanganicae and Limnothrissa miodon and the centropomid Lates stappersii) of Lake Tanganyika is from research carried out in localised areas. This makes it difficult to extend the results to the whole lake. Consequently, there is the need to study the pelagic fish resources on a lake-wide basis using the same data collection procedures. Within the framework of an international fishery research project, data from the commercial fisheries targeting the pelagic fish stocks were simultaneously collected at various sampling sites in the riparian countries. Fishery-independent data were also obtained from lake-wide research surveys. The life histories of the three fish species appear to be similar throughout the lake. However, fish distribution across the lake is very uneven. The clupeid S. tanganicae mostly occur in the northern half of the lake and is much reduced in southern areas. This appears to be a recent contraction of the distribution range of this species. Limnothrissa miodon is more evenly distributed than S. tanganicae. The two species have a different inshore-offshore, size-related distribution across the lake. Nursery grounds of the first are close to the shore while those of S. tanganicae are in open, pelagic waters. With increase in size, S. tanganicae tend to move inshore while large L. miodon display the opposite movement. Lates stappersii stock, although relatively common, tends to be at higher concentration in the deep, steep central and southern basins. The feeding ecology of L. stappersii varies depending on the area and prey availability, but is mainly based on S. tanganicae and pelagic shrimps. Local occurrence of S. tanganicae is associated with that of copepod prey. The fish stocks experience different exploitation rates across the lake. While the fishing pressure is not excessive in the most of the lake areas, in others local overfishing is taking place. The biological characteristics of the pelagic fish species are discussed for the management of the lake fisheries. Fisheries management options are formulated on the basis of the assessment of the current exploitation levels.
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Earl, Julie. "The molecular ecology of methanogens in a hypereutrophic lake." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250268.
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Marijnissen, S. A. E. "Lake Tanganyika crabs evolution, ecology, and implications for conservation /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/54978.
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Auman, Ann Jennifer. "Molecular analysis of methanotroph ecology in Lake Washington sediment /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/11522.
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Averbeck, Christiane. "Population ecology of impala (Aepyceros melampus) and community based wildlife conservation in Uganda." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964072017.
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Kaunda, Emmanuel Kamlipe Watson Hawkins. "Feeding ecology of Bathyclarias nyasensis (Siluroidei: Claridae) from Lake Malawi." Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1005126.
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In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
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Trumpickas, Justinas. "Impacts of introduced piscivores on lake fish assemblages." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95239.
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Introduced predators can have strong negative effects on native prey populations; the severity of this impact can be greater than that of native predators and can change with multiple predator introductions. I examined relationships between native fish assemblages and five widely introduced piscivorous fishes: largemouth bass Micropterus salmoides, northern pike Esox lucius, rock bass Ambloplites rupestris, smallmouth bass Micropterus dolomieu and walleye Sander vitreus. Analysis of data from over 9000 lakes in Ontario, Canada, revealed that the presence of these piscivores reduces prey species richness, and that the magnitude of this impact varies with predator species and predator richness. There was no difference in the effects of introduced and native smallmouth bass populations on prey richness. Results from a multi-lake field study at Algonquin Park (Ontario) suggested predators structure nearshore fish assemblages, although to a lesser degree than spatial and environmental factors. There was little evidence that fish assemblages change through space and time with increased predator richness, implying functional redundancy of later invaders.L'introduction de prédateurs peut avoir de nombreux impacts négatifs sur les populations de proies indigènes; la sévérité de cet impact peut être plus important que celle que peuvent avoir les prédateurs indigènes et peut varier lors de l'introduction de plusieurs prédateurs. J'ai étudié la relation qu'il existe entre les assemblages de poissons indigènes et cinq espèces de prédateurs piscivores introduites à grande échelle: l'achigan à grande bouche Micropterus salmoides, le grand brochet Esox lucius, le crapet de roche Ambloplites rupestris, l'achigan à petite bouche Micropterus dolomieu et le doré jaune Sander vitreus. L'analyse de données provenant de plus de 9000 lacs situés en Ontario, Canada, a révélé que la présence de ces poissons piscivores réduit la richesse spécifique au niveau des proies, et que l'amplitude de cet impact varie en fonction des espèces de prédateurs et de la richesse de ces prédateurs. Il n'y a pas de différence entre l'impact que produisent les achigans à petite bouche introduits et indigènes sur la richesse des proies. Les résultats d'une enquête de multi-lac sur le terrain au Parc Algonquin (Ontario) ont suggéré que les prédateurs structurent les assemblages des poissons du littoral, bien qu'à un degré moindre que des facteurs spatiales et environmentales. Peu de preuves qui indiquent que l'assemblage de poissons change avec le temps et l'espace en fonction d'une augmentation de la richesse des prédateurs, ce qui laisse supposer qu'il y a une redondance fonctionelle des espèces envahissantes qui ont colonisé les lacs plus tard.
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Guimarães, Wesley Luiz. "Contribuição dos ovos de resistência de cladocera (Crustacea: Branchiopoda) para a recolonização de ambientes lacustres temporários /." São José do Rio Preto, 2016. http://hdl.handle.net/11449/136465.
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Orientador: Maria Stela Maioli Castilho NollCoorientador: Eliana Aparecida Panarelli
Banca: Cláudia Costa Bonecker
Banca: Maria Cristina Basílio Crispim da Silva
Resumo: Planícies de inundação são áreas úmidas onde podem ser encontradas as lagoas marginais. Devido ao período de seca e a sua baixa profundidade, estas lagoas podem apresentar caráter temporário com ocorrência sazonal. Tal perturbação pode levar algumas populações zooplanctônicas, como as de cladóceros, a entrarem em estado de dormência, produzindo os ovos de resistência que se depositam no sedimento seco formando um banco de ovos. Quando as lagoas voltam a encher, a comunidade de cladóceros rapidamente se reestabelece, provavelmente como resultado da eclosão dos ovos presentes no sedimento. Detectar espécies de cladóceros que produzem os ovos de resistência como estratégia para recolonização, bem como os fatores que influenciam a eclosão dos ovos, pode auxiliar na compreensão do papel do banco de ovos como fonte de biodiversidade zooplanctônica em lagoas marginais. O objetivo neste estudo foi verificar o potencial de cladóceros para recolonização de lagoas marginais temporárias, por meio da eclosão de ovos de resistência em condições experimentais específicas. A comunidade zooplanctônica foi amostrada em quatro lagoas marginais localizadas na planície de inundação do Rio Turvo. As amostragens dos cladóceros planctônicos foram feitas com rede de plâncton de 50 μm de malha, antes e após um período de seca. Além disso, também foram medidos parâmetros físicos e químicos: profundidade, transparência, temperatura, pH, condutividade, OD, clorofila e material em suspensão. Para a realização dos experimentos de eclosão dos ovos de resistência em laboratório, amostras do sedimento das lagoas foram obtidas com Corer (4,5 cm de diâmetro), durante a estação seca. Duas metodologias foram testadas para indicar qual a mais eficaz para a eclosão: 1. Tratamento ambiente: frascos com sedimento e água do rio Turvo mantidos em condições...
Abstract: Floodplains are wetlands where the oxbow lakes can be found. Due of the dry season and its shallow depth, these lagoons can present seasonal occurrence. Such disruption can lead some zooplankton populations, such as cladocerans, to enter in dormancy, producing resting eggs that are deposited in dry sediment forming a bank of eggs. When the lagoons back to fill the cladoceran community quickly restores, probably as a result of the hatch of eggs present in the sediment. To detect species of cladocerans that produce resting eggs as a strategy for recolonization, as well as the factors influencing the eggs hatch, may help understanding the egg bank's role as zooplankton biodiversity source in lagoons. Our goal in this study was to investigate the potential of cladocerans to recolonize of temporary lagoons, through the hatching of resting eggs in specific experimental conditions. The zooplankton community was sampled in four lagoons located in the Turvo River floodplain. Sampling of planktonic cladocerans were taken by a plankton 50 µm mesh net before and after the drying lagoons. Physical and chemical parameters as depth, transparency, temperature, pH, conductivity, OD, chlorophyll and suspended material were also measured. For the hatching experiments of resting eggs in laboratory, sediment from lagoons were sampled using a corer (4.5 cm diameter), during the dry season. Two methods were tested to indicate the most effective for the hatching: 1. Environment Treatment: bottles with sediment and water from the Turvo river kept at ambient conditions; 2. Chamber Treatment: bottles with sediment and water from the Turvo river kept under controlled conditions in a growth chamber (23 ° C and photoperiod 12:12). Every two days each replica was analyzed for physical and chemical parameters and the verification of cladocerans newly hatched. After two weeks these procedures were ...
Mestre
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Canny, Laura L. "Determining aquatic macrophyte response to human perturbation in watersheds and along lakeshores of Wisconsin lakes and the tolerance levels of individual species to environmental gradients /." Link to full text, 2007. http://epapers.uwsp.edu/thesis/2007/Canny.pdf.
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Amidon, Zachary J. "Lake Whitefish Spawning Locations and Overwinter Egg Survival in Western Lake Erie." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1547033485879165.
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Marshall, C. Tara. "Seasonal patterns in chlorophyll-a concentrations for temperate lakes." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66186.
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Newbrey, Jennifer L. "Effect of lake characteristics and human disturbance on lacustrine habitat selection by piscivorous birds in northern Wisconsin /." Link to abstract, 2002. http://epapers.uwsp.edu/abstracts/2002/Newbrey,J.pdf.
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Buktenica, M. W. "Ecology of kokanee salmon and rainbow trout in Crater Lake, a deep ultraoligotrophic caldera lake (Oregon) /." View full-text version online through Crater Lake Digital Research Collection, 1988. http://craterlakelib.oit.edu/u?/craterlake,195.
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Rombold, John Sumner. "The fate of canopy water in the Findley Lake basin, WA /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5574.
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Dodson, Susan Boyd. "Eutrophication Potential of Reclaimed Wastewater: An Ecological Study of Water Reuse in an Urban Texas Reservoir." Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc935568/.
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This study determined effects of addition of secondarily treated municipal wastewater effluent on an urban reservoir receiving system. Monthly water quality monitoring of the receiving reservoir and the wastewater, chemical analysis, and monthly laboratory algal assays, were conducted from September 1984 to September 1985. The nutrient status and algal growth potential of the receiving water and the wastewater confirmed the biostimulatory properties of the wastewater. Field validation studies were conducted using limnocorrals. Tertiary treatment of the wastewater using chemical coagulation precipitation with alum and ferric chloride reduced phosphorus concentrations in the wastewater to levels which supported significantly less algal biomass than untreated wastewater. These studies indicate ferric chloride to be a more effective coagulant for phosphorous removal alum.
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Bryhn, Andreas Christoffer. "Quantitative Understanding and Prediction of Lake Eutrophication." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8593.
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Many lakes around the world have been exposed to increased nutrient input from anthropogenic sources such as sewage discharge and runoff from fertilised agricultural areas. This has led to eutrophication, manifested as intensified algal blooms, murky waters, oxygen depleted lake bottoms, and alterations of considerable parts of the foodweb. However, many of these lakes have also recovered, due to improved nutrient abatement techniques and to an improved quantitative scientific understanding of eutrophication and its causes. General, predictive models have played a crucial role in the latter development, as they have made it possible to quantitatively assess expected ecosystem changes from various planned actions against eutrophication. The present thesis has been aimed at improving the domain of validity and predictive power of a general, dynamic total phosphorus (TP) model (LakeMab) and to provide the basis for constructing a similar model for total nitrogen (TN). Among the findings in the thesis is that dissolved nitrogen gas is probably always available in excess for nitrogen fixation and nitrogen modelling in eutrophication contexts. Two papers have laid the ground for improved nutrient modelling in calcareous lakes, where sedimentation is particularly pronounced. Static models for predicting concentrations of particulate phosphorus, nitrogen, and organic carbon have been presented that may be incorporated into sedimentation algorithms in dynamic nutrient models. Boundary conditions for various flux algorithms have made it possible to greatly expand the domain of LakeMab for TP. The typical uncertainty of TP concentration values is 17% when predicted with LakeMab, whereas the uncertainty in predictions using older, static models is about twice as high. LakeMab may be very useful for resolving practical issues such as predicting climate-induced eutrophication and drawing up operational guidelines for achieving good water quality as prescribed by, e.g., the European Water Framework Directive.
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Rowland, Jennifer M. "Restoration ecology of Cirsium pitcheri along Lake Huron sand dunes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ42096.pdf.
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Procter, R. M. "The feeding ecology of three species of lake-dwelling leeches." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380088.
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Vest, Josh L. "Winter Ecology of Waterfowl on the Great Salt Lake, Utah." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2051.
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I designed a suite of studies in coordination with Utah Division of Wildlife Resources (UDWR) to evaluate waterfowl use of the GSL in winter and ecological aspects associated with GSL use. These studies provided insight into key information gaps previously identified by UDWR regarding management of GSL resources. Population surveys indicated total duck abundance was low when GSL surface elevations were low and wetland resources diminished because of persistent drought in the system. Also, ducks appear to use hypersaline parts of GSL more when freshwater habitats are limited from either drought or ice conditions. Common goldeneye, northern shoveler, and green-winged teal exhibited the most use of hypersaline areas. Dietary evaluations indicated all three species feed on hypersaline invertebrates from GSL to meet energetic and nutritional needs in winter. Brine shrimp cysts were important foods for northern shoveler and green-winged teal. Fat levels of ducks are important determinants of survival and fitness. Fat reserves of goldeneye were generally lower in the winter when both GSL and wetland habitat resources were lower. Results suggest brine fly larvae productivity, freshwater habitat availability, and temperature and wind speed likely play a more prominent role in goldeneye fat reserves than osmoregulation. Also, common goldeneye and northern shoveler using the GSL apparently accumulated biologically concerning amounts of mercury and selenium during winter. However, further research is needed to evaluate the effect of these elements on GSL ducks.
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Lymer, David. "Significance and Diversity of Lake Bacteriophages." Doctoral thesis, Uppsala : Uppsala universitet, Universitetsbiblioteket, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9499.
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Chagnon, Guillaume. "The relative contribution of pelagic primary production to the littoral food web of lakes /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31205.
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A dual stable isotope approach (delta13C and delta15N) was used to assess the importance of pelagic organic carbon in littoral secondary production and explore its predictability. Forty-seven sites were sampled in Lake Memphremagog (Quebec--Vermont) to characterize the isotopic position of the primary producers and filter-feeding freshwater mussels, as well as macrophyte biomass, chlorophyll-a concentration, and site exposure. The different sites spanned a wide range in the three environmental variables. For each site, littoral, terrestrial, and pelagic contributions to the diet of the mussels were calculated from mussel isotopic position, corrected for trophic enrichment. The mean contributions were: littoral---8%, terrestrial---27%, and pelagic---65%. However, the magnitude of the pelagic contribution was not related to macrophyte biomass, site exposure or chlorophyll-a concentration. The finding that the unionid mussels, a major littoral zone filter-feeder, obtain about two-thirds of their nutrition from pelagic zone particles washed into the littoral zone provides evidence for a close coupling in carbon flow of the littoral and pelagic zone. This study represents an important step towards a better understanding of carbon flow in aquatic food webs.
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Jackson, Leland J. "Seasonality, sinking and the chlorophyll maximum of an oligotrophic British Columbia lake." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27967.
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A field investigation was carried out over two seasonal periods on an oligotrophic coastal British Columbia lake to determine the role of sinking in the formation of the chlorophyll maximum as well as some aspects of phytoplankton seasonality.
Sinking rates of two diatoms were measured and found to be highest in the epilimnion and lowest at the depth of the chlorophyll maximum. Light affected sinking rate as well as the position of the chlorophyll maximum. The chlorophyll maximum formed at 10-12 m following the onset of seasonal thermal stratification and descended to ca. 22 m for the summer. A major factor in the formation of the chlorophyll maximum is the decrease of phytoplankton sinking rate at depth.
Rhizosolenia eriensis is one of the first phytoplankters to bloom in the spring. Small flagellates (3-15 um) and occasionally Dinobryon sp. were also important numerically. In the summer Cyclotella spp. displaced R. eriensis as the dominant diatom in the epilimnion. The relative timing of seasonal maxima of blooms of various species remained similar during the two years investigated.
Lake fertilization affected the phytoplankton standing stock. R. eriensis did not greatly benefit from fertilization since it sank out of the epilimnion and became a major constituent of the chlorophyll maximum before fertilization. Because of its large size and low C : cell volume ratio due to a large vacuole, R. eriensis is probably not a good food source for zooplankton.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Johannsson, V. "Life history strategies of blackflies (Simulidae) in Icelandic lake-outlets." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372319.
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Belinsky, Tammy L. "The effects of lake dymanics on the water quality of Abel Lake Reservoir." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43832.
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The Abel Lake Reservoir in Stafford County, Virginia, was investigated to evaluate the lake's temporal and spatial dynamics with respect to water quality and water treatment problems. A limnological survey was conducted. The survey included all conventional parameters for the characterization of hydrodynamics and lake-water quality.
Abel Lake was found to be a typical temperate-zone lake that stratifies thermally in the summer, and the hypolimnetic water quality subsequently degrades with the depletion of oxygen. The lake then circulates in the fall in a process that begins in the shallow, upstream area of the lake and progresses downstream gradually until the deepest regions have circulated. The circulation process brings poor quality water from the hypolimnion to the surface where it is drawn into the treatment facility and creates treatment problems.
Results also show that algal growth and nutrient concentrations were moderate during the study, however, the potential for cultural eutrophication is present should unmonitored development of the watershed occur.Master of Science
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Moore, Joel Grant. "Diversity, productivity, and physiology of microorganisms in the stream-moat-lake transition of Lake Bonney, Antarctica." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/moore/MooreJ0507.pdf.
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Coahran, David Alan. "Effects of liming on plankton and young-of-the-year bluegill growth in Flat Top Lake, West Virginia." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41973.
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The responses at three trophic levels (phytoplankton, zooplankton, young-of-the-year bluegill) were compared between a limed and unlimed arm in a moderately fertile, circumneutral reservoir that was sensitive to acidification, but had not yet shown signs of damage. The east arm (25.5 ha) of Flat Top Lake was treated with 28.8 dry metric tonnes of calcite using slurry box technology between July 13-20, 1987. The design was confounded because calcite dissolution products diffused into the unlimed (west) arm after the treatment which made total alkalinity similar between the arms within 1 month. Phytoplankton gross productivity and chlorophyll a was similar between the arms for the pre- and post-treatment samples as well as for the period after the treatment when total alkalinity was relatively higher in the limed arm. Zooplankton biomass was higher in the unlimed than limed arm in the pre-treatment samples but was similar between the arms in the post-treatments samples; however, the changes in zooplankton biomass after treatment in the limed arm could not be attributed to the treatment. Phytoplankton community composition for the common netplankton and nannoplankton was similar between the limed and unlimed arms for the combined pre- and post-treatment samples: however, Gemellicystis spp., Gloeocystis spp., and Dinobryon spp. showed an order of magnitude higher density in the limed relative to the unlimed arm on the initial post-treatment sample. This difference, as well as the observed post-treatment differences in zooplankton community composition between the two arms could not be attributed to the treatment because there were minimal impacts on nutrient levels (e.g., CO2, total phosphorus) and zooplankton-phytoplankton interactions. Lake transparency was significantly deeper in the limed arm relative to the unlimed arm for the post-treatment samples; however, a corresponding lower dissolved organic carbon concentration was not measured in the limed arm. Young-of-the-year bluegill (e.g., primarily those 15-20 d old) showed significantly higher growth rates in the unlimed arm during the period when total alkalinity was higher in the limed arm, apparently due to a higher density of suitable pelagic zooplankton in the unlimed arm during this period. In conclusion, no significant positive or negative responses to the treatment were detected because of trophic level interactions. The high pre-treatment pH (7.07), small change in post-treatment pH, low dissolution percentage (8-10%), the inability of the sediment dose to neutralize the acidic sediments and induce phosphorus release, and phosphorus rather than carbon dioxide limited primary productivity were the main factors why no significant post-treatment biological responses were detected.Master of Science
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Haws, Emily Sarah. "Ecology of Culturable Organisms at Rozel Point, Great Salt Lake, Utah." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/857.
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The study of organisms from extreme environments is an emerging field of research with applications to multiple scientific areas. One of these extreme environments is Great Salt Lake (GSL), whose microbiology has yet to be extensively studied. This dynamic and unique environment offers an excellent opportunity to increase understanding of hypersaline ecology. Cultivation of microorganisms remains an important part of ecology research, as it is essential for understanding microbial physiology. We report here the culturing and characterization of isolates from Rozel Point, located on the northeastern shore of Great Salt Lake. This site was chosen because of the presence of petroleum seeps at Rozel Point and the extreme salinity of the North Arm of GSL. We hypothesize that culturing at GSL will reveal a diverse prokaryotic population, with both commonly isolated and novel organisms. We would predict that prokaryotes at GSL will share many features in common with other hypersaline microbial communities, but that given the distinctive properties of the site, there will be unique characteristics as well. Samples were taken from Rozel Point and cultured using direct plating, enrichment cultures, and dilution cultures with a variety of minimal and complex halophilic media. Fluorescence in situ hybridization (FISH) was used to examine abundance of cultured organisms in the environment. Culturing and characterization has revealed both isolates novel and previously uncultured, with many unique characteristics. FISH demonstrated that, unlike most environments, in GSL the dominant species are culturable. These results show the value of culturing in discovering new organisms and demonstrating diversity at the microbial level. Culturing of these organisms will allow for further research to be done on microbial processes that occur in this system and the unique properties of halophilic microbes.
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Harrod, Chris. "The ecology of a threatened fish : the pollan (Coregonus autumnalis) in Lough Neagh, Northern Ireland." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268852.
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Ness, Kirsten L. "The Effects of Shoreline Development on Lake Littoral and Riparian Habitats: Are Shoreline Protection Regulations Enough?" Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/NessKL2006.pdf.
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She, Nian. "Chaos in aquatic systems /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/6370.
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Urban, Rebecca Anne. "An invasive macrophyte creates cascading ecosystem effects through suppression of a native isoetid." Diss., Online access via UMI:, 2008.
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Mubamba, Raphael. "The ecology of the coregonid fishes in the English Lake District." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329430.
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Haws, Emily S. "Ecology of culturable organisms at Rozel Point, Great Salt Lake, Utah /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1741.pdf.
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Cooke, Gavan M. "The behavioural ecology of aggression in Lake Malawi haplochromine cichlid fish." Thesis, Bangor University, 2012. https://research.bangor.ac.uk/portal/en/theses/the-behavioural-ecology-of-aggression-in-lake-malawi-haplochromine-cichlid-fish(8a0e6fe2-15b6-42f5-9324-7749b44f3dad).html.
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Aggression is ubiquitous in the animal kingdom and a major field of investigation within the area of behavioural ecology. The haplochromine cichlid fish have been used extensively in studies relating not only to the behavioural ecology of aggression but also with respect to how aggression may play a role in the spectacular diversity found within the African Great Lakes. In the first half of this thesis, I investigate the nature of aggression within the rock dwelling fish of Lake Malawi. Aggression biases within polymorphic populations are initially investigated with field work determining the consequences of rare morph advantage. This is followed by experiments determining which cues males and females may use; lastly a pair of recently diverged allopatric species is studied to determine what may happen should secondary contact occur. The second half of this thesis focuses on the behaviorual ecology of female aggression. Females exhibiting the ancestral condition of post brood care are compared to a species with the more derived condition of no post release care. Non-maternal aggression is investigated with comparisons of the type of behavior used by males and females. When and why females are aggressive is also investigated. The results of this thesis suggest that overall a common morph bias may exist in some populations and the consequences are manifested in a rare morph advantage. Colour is important in aggression biases but potentially not limited to the dorsal region. Females and males use different kinds of aggressive behaviors and brooding females are able to vary levels of aggression towards different types of threat.
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Lambourne, Gail. "The ecophysiology of Gloeotrichia echinulata in Blashford Lake." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265422.
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Balirwa, John Stephen. "Lake Victoria wetlands and the ecology of the Nile Tilapia, Oreochromis niloticus Linné /." Rotterdam : A.A. Balkema, 1998. http://www.loc.gov/catdir/enhancements/fy0916/99496402-d.html.
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Harlin, Hugo. "2D Modelling of Phytoplankton Dynamics in Freshwater Lakes." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388868.
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Phytoplankton are single celled organisms capable of phytosynthesis, and are present in all the major oceans and lakes in the world. Phytoplankton contribute to 50% of the total primary production on Earth, and are the dominating primary producer in most aquatic ecosystems. This thesis is based on the 1D deterministic model by Jäger et. al. (2010) which models phytoplankton dynamics in freshwater lakes, where phytoplankton growth is limited by the availability of light and phosphorus. The original model is here extended to two dimensions to include a horizontal dimension as well as a vertical dimension, in order to simulate phytoplankton dynamics under varying lake bottom topographies. The model was solved numerically using a grid transform and a finite volume method in MATLAB. Using the same parameter settings as the 1D case studied by Jäger et. al. (2010), an initial study of plankton dynamics was done by varying the horizontal and vertical diffusion coefficients independently.
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Huddleston, Amara Lynn. "The Influence of Ice Cover on the Coupling between Lake Erie Larval Walleye and their Prey." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1532082401065932.
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Schmidt, Brian A. "Determining the Habitat Limitations of Maumee River Walleye Production to Western Lake Erie Fish Stocks." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1463067261.
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