Дисертації: "Influence of lakes"

1

Littlejohn, Carla Louise, and n/a. "Influence of Artificial Destratification on Limnological Processes in Lake Samsonvale (North Pine Dam), Queensland, Australia." Griffith University. Australian School of Environmental Studies, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050211.133123.

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Artificial destratification equipment was installed in Lake Samsonvale in October 1995 to reduce the biomass of potentially toxic cyanobacteria in the reservoir. This study was undertaken to investigate the effects of the destratifier on the limnological processes occurring in the lake and to determine if operation of the destratifier has been effective at reducing the summer populations of Cylindrospermopsis raciborskii and Microcystis aeruginosa. The study showed that artificial destratification of Lake Samsonvale has been successful at reducing the surface to bottom thermal gradient and increasing dissolved oxygen concentrations at depth. While the destratifier has not resulted in the lake becoming completely 'mixed' during summer, it has weakened resistance to mixing from meteorological events, which has led to a reduction in mean concentrations of total and dissolved phosphorus during summer. Although not conclusive, it is likely that the influence of the destratifier is restricted to a narrow radial distance around the bubbleplumes during periods of strong stability, so internal loading may continue to provide a substantial source of nutrients for cyanobacterial growth, particularly in regions of the lake less influenced by the destratifier. The results for cyanobacteria are less encouraging. Despite the reduction in concentrations of dissolved phosphorus, the destratifier has not been effective at reducing summer populations of C. raciborskii and M. aeruginosa. On the contrary, there is evidence to suggest that populations have actually increased which could have serious operational consequences for the lake by mixing the previously buoyant cyanobacteria to the level of the water off-take. The growth season for C. raciborskii has been extended by up to 3 months and population onset now occurs during spring. This increase in spring populations could be a result of significantly greater baseline populations during winter, or the earlier germination of akinetes as a result of increased sediment temperatures. The seasonal successional relationship between C. raciborskii and M. aeruginosa appears to have shifted from one of alternating dominance between the two species to one of co-existence under conditions of intermediate disturbance. It was concluded that although the continued operation of the destratifier may prove useful to minimise water treatment costs through reducing internal loading of dissolved constituents, it has not been successful in achieving its original objective of controlling cyanobacterial populations in the lake.

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2

Littlejohn, Carla Louise. "Influence of Artificial Destratification on Limnological Processes in Lake Samsonvale (North Pine Dam), Queensland, Australia." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/365764.

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Artificial destratification equipment was installed in Lake Samsonvale in October 1995 to reduce the biomass of potentially toxic cyanobacteria in the reservoir. This study was undertaken to investigate the effects of the destratifier on the limnological processes occurring in the lake and to determine if operation of the destratifier has been effective at reducing the summer populations of Cylindrospermopsis raciborskii and Microcystis aeruginosa. The study showed that artificial destratification of Lake Samsonvale has been successful at reducing the surface to bottom thermal gradient and increasing dissolved oxygen concentrations at depth. While the destratifier has not resulted in the lake becoming completely 'mixed' during summer, it has weakened resistance to mixing from meteorological events, which has led to a reduction in mean concentrations of total and dissolved phosphorus during summer. Although not conclusive, it is likely that the influence of the destratifier is restricted to a narrow radial distance around the bubbleplumes during periods of strong stability, so internal loading may continue to provide a substantial source of nutrients for cyanobacterial growth, particularly in regions of the lake less influenced by the destratifier. The results for cyanobacteria are less encouraging. Despite the reduction in concentrations of dissolved phosphorus, the destratifier has not been effective at reducing summer populations of C. raciborskii and M. aeruginosa. On the contrary, there is evidence to suggest that populations have actually increased which could have serious operational consequences for the lake by mixing the previously buoyant cyanobacteria to the level of the water off-take. The growth season for C. raciborskii has been extended by up to 3 months and population onset now occurs during spring. This increase in spring populations could be a result of significantly greater baseline populations during winter, or the earlier germination of akinetes as a result of increased sediment temperatures. The seasonal successional relationship between C. raciborskii and M. aeruginosa appears to have shifted from one of alternating dominance between the two species to one of co-existence under conditions of intermediate disturbance. It was concluded that although the continued operation of the destratifier may prove useful to minimise water treatment costs through reducing internal loading of dissolved constituents, it has not been successful in achieving its original objective of controlling cyanobacterial populations in the lake.
Thesis (Masters)
Master of Philosophy (MPhil)
Australian School of Environmental Studies
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3

Kerimoglu, Onur. "Influence Of Large Scale Atmospheric Systems On Hydorology And Ecology Of Turkish Lakes." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609272/index.pdf.

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Impacts of climatic changes on in-land waters of Turkey is a topic that has not been sufficiently investigated yet. In this study, some exploratory work have been performed to form the core of further studies on the subject. EOF (Empirical Orthogonal Function) analysis has been applied to SLP (Sea Level Pressure) field with a wide coverage (20-70N, 50W-70E). The dominant sources of variability in this atmospheric system have been shown to be driven by 3 circulation indices, NAO (North Atlantic Oscillation), EAWR (East Atlantic - West Russia) and EA (East Atlantic) patterns. Linkages between this atmospheric system and the hydro-meteorological properties (data compiled from governmental organizations) of major Turkish lake ecosystems has been investigated with use of ordinary correlation analysis and CCA (Canonical Correlation Analysis). The results revealed the heavy forcing of large scale SLP field on regional temperature and E--P (evaporation minus precipitation) fields. The 15-year data set of Lake Mogan, as the longest available found, was used to exemplify the approaches and methodologies that can be employed for understanding the influence of climate variability on biological properties of lakes. It was suggested that temperature and salinity, being effective on phytoplankton and zooplankton groups, mediate the climatic impacts in Lake Mogan.

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4

Thompson, Lisa C. "The influence of hydraulic retention time on planktonic biomass in lakes and reservoirs /." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56754.

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Hydraulic retention time (HRT) might contribute to the substantial variation in phosphorus-chlorphyll and chlorophyll-zooplankton models because rapid flushing might depress plankton development. However, for a world-wide data set. HRT was not correlated with chlorophyll. Total phosphorus had no effect on chlorphyll when hypereutrophic sites were considered separately, but chlorophyll was negatively related to HRT. Short term HRT, averaged over periods up to one month, was not correlated with chlorophyll, or zooplankton biomass, in seven impoundments on the St. Lawrence and Ottawa Rivers. The size distribution of algae was not affected by HRT. The proportion of rotifer to total zooplankton biomass was positively related to HRT, but this trend disappeared when nauplius biomass was removed from the total. These results indicate that rapid flushing does not necessarily reduce planktonic biomass and that short term HRT is not useful for the prediction and management of planktonic biomass in these systems.

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5

Edwards, William J. "Impacts of the Zebra Mussel (Dreissena Polymorpha) on Large Lakes: Influence of Vertical Turbulent Mixing." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392139735.

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6

Langlois, Peter William. "The influence of trophic state, thermal structure and winterkill on littoral macroinvertebrate communities in Boreal Plain lakes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0013/MQ60136.pdf.

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7

Li, Wei. "INFLUENCE OF ENVIRONMENTAL DRIVERS AND INTERACTIONS ON THE MICROBIAL COMMUNITY STRUCTURE IN PERMANENTLY STRATIFIED MEROMICTIC ANTARCTIC LAKES." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1469757316.

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8

Johnson, Cody R. "Consumer-Driven Nutrient Recycling in Arctic Alaskan Lakes: Controls, Importance for Primary Productivity, and Influence on Nutirient Limitation." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/417.

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In lakes, fish and zooplankton can be both sources and sinks of nitrogen (N) and phosphorus (P) through the consumption of organic N and P, and subsequent excretion of bioavailable inorganic forms. These source/sink dynamics, known as consumer-driven nutrient recycling (CNR), may, in turn, control the availability of potentially limiting nutrients for algal primary production. In this dissertation I investigate the importance and controls of CNR as a source of inorganic N and P for primary production (Chapter 2). I then examine zooplankton CNR as a mechanism for increasing nutrient mean resident time (MRT) in the mixed layer of lakes (Chapter 3). Finally, I assess whether zooplankton communities dominated by different taxa can affect N versus P deficient conditions for phytoplankton production through differential N and P recycling rates (Chapter 4). Direct excretion of N and P by fish communities was modest in arctic lakes, and accounted for < 4 % of the N and P required for primary production. Recycling of N and P by zooplankton communities was relatively high, and the fraction of algal N and P demand supplied by zooplankton CNR ranged from 4 - 90% for N and 7 - 107% for P. MRT of 15N, measured in the mixed layer of an arctic lake, was ~16 days, compared to 14 days predicted by a ecosystem model simulation with zooplankton N recycling and 8 days in a model simulation where zooplankton N recycling was absent. The 75% increase in N MRT between model simulations with and without zooplankton recycling suggests that zooplankton N recycling is an important mechanism for retaining N in lake ecosystems. I observed relatively high negative correlations between precipitation and phytoplankton N (r = -0.33) and P (r = -0.30) deficiencies. I also observed a significant positive correlation (r = 0.42, p = 0.03) between zooplankton communities with higher copepod biomass, relative to cladoceran biomass, and phytoplankton N-deficient conditions. These results suggest that when precipitation is high N and P deficiency is low in the phytoplankton. When precipitation is low, however, zooplankton communities composed primarily of copepods contribute to N-deficient conditions for phytoplankton production.

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9

Kirkpatrick, Heather. "The Ecological Influence of the Non-Indigenous Zooplankter Eubosmina coregoni in Lake Ecosystems." Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1302263925.

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10

Anthony, James Lee. "The influence of turbulence, temperature, and nutrient concentration gradients on sediment-water exchanges of nitrogen and phosphorus in lakes." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3284439.

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11

Papadopoulou, Sofia. "The influence of diel cycles on the bacterial community composition of two boreal lakes : A case study in Jämtland." Thesis, Uppsala universitet, Limnologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447209.

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In the Boreal region, the length of day and night varies extremely over the year and organisms are exposed to different diel (24 h) fluctuations of light and temperature. Among them are pelagic populations of bacteria that are ubiquitous in freshwater ecosystems. The structure of prokaryotic assemblages in lakes is regulated by both abiotic and biotic parameters known to have diel patterns; yet, knowledge on changes of the active bacterial community composition (aBCC) over diel cycles is limited, especially at short temporal scales. Here, measurements of physicochemical parameters, nutrient levels and chlorophyll a concentrations, characterization of the carbon pool and 16S rRNA sequencing were used to elucidate the aBCC in a peat bog and the oligotrophic lake Klocka in Jämtland county, Sweden. I show that the activity of bacterioplankton communities remained relatively stable at 6-h intervals and did not follow any diel patterns during an uneven light regime period in June. However, the activity of peat bog communities changed in a cyclic pattern over three diel cycles during an even light period in September, whereas diel changes did not substantially differentiate between sampling periods and among depths in Klocka. The results of the thesis provide valuable insights into the importance of diel cycles in bacterial diversity and community dynamics in lentic habitats.

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12

Welsh, Paul Gregory. "Influence of dissolved organic carbon on the speciation, bioavailability and toxicity of metals to aquatic biota in soft water lakes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21397.pdf.

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13

Rusak, James. "Variability in the zooplankton of north-temperate lakes, its estimation, spatial and temporal extent, synchrony, and the influence of environmental change." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/NQ56267.pdf.

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14

Rushworth, Gary Stephen. "The influence of variations in reedswamp structure and extent upon macroinvertebrates and associated ecological processes within the littoral zone of lakes." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8403/.

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Reedswamps are a key feature of the shallows of many lakes, influencing biodiversity and functioning, but are in decline in lakes throughout Europe for reasons that are unclear. Metadata analysis of data extending over 100 years suggested that multiple stressors were implicated in reedbed decline within Windermere (UK), and that the influences of individual stressors should be investigated by comparing genetic diversity and environmental factors across lakes within the same catchment or region. Furthermore, the consequences of changes in reedswamp structure and coverage for whole lake functioning is an important gap in knowledge for Windermere and many other lakes. Macroinvertebrate data from two lakes in the Windermere catchment were used to investigate the influence of reedswamp habitat upon biodiversity, and key ecological processes such as decomposition. A semi-quantitative survey highlighted the importance of reedswamp size, shape, and structure in determining the ways in which macroinvertebrates influence lake functioning. Collection of macroinvertebrates from a wide range of niches along vertical and horizontal axes using a hand-net was a unique approach, and provided novel insights into key ecological processes. For example, seasonal influences were modified by structural heterogeneity, and position within reedswamps. This was supported by the findings of a field-based litter bag experiment; differences in macroinvertebrate seasonal dynamics were associated with differences in litter structure from two species of reed. Furthermore, there were interspecific differences in seasonal patterns of litter deposition. Both macroinvertebrate methods were efficient and effective, and should form the basis of a standardised sampling protocol for the shallows of lakes. This body of research on local variations (~8 m) demonstrates the need for a detailed understanding of how structural heterogeneity influences whole lake functioning. This should include comprehensive food webs that include vertebrates, macroinvertebrates, macrophytes, algae, and microbes for reedswamp and other key habitats.

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15

Baranov, Viktor. "Influence of bioturbation on sediment respiration in advection and diffusion dominated systems." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18792.

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Ökosystem-Ingenieure sind Organismen, deren Auswirkung auf die Funktion von Ökosystemen im Vergleich zu ihrer Anzahl und Biomasse überproportional groß ist. Ein klassisches Beispiel für Ökosystem-Ingenieure sind grabende Organismen, deren Aktivitäten (Bioturbation) sowohl die Sedimentmatrix als auch das Porenwasser in aquatischen Sedimenten beeinflussen. Solche Tiere wirken auf eine große Anzahl von biogeochemischen Prozessen in benthischen Ökosystemen ein, unter anderem auf die aerobe Atmung (Respiration). Die Respiration aquatischer Sedimente umfasst häufig über 50 % der gesamten Respiration von aquatischen Systemen und spielt eine große Rolle im globalen Kohlenstoffkreislauf. Die vorliegende Doktorarbeit beschäftigt sich mit den Auswirkungen der physikalischen Umwelt (Sedimenteigenschaften, am meistens hydraulischer Leitfähigkeit) auf die mikrobielle Respiration von Sedimenten, in denen Bioturbation durch Chironomidenlarven stattfindet. Um die Auswirkungen von Bioturbation auf Respiration zu messen und zu identifizieren, wurde eine neue Messmethode entwickelt (Kapitel 4.1). Kapitel 4.2 zeigt, dass der Einfluss von Bioturbation auf die Respiration des Sediments mit zunehmender Temperatur ansteigt. Kapitel 4.3 belegt, dass Resazurin auch für die Messung der Respiration in marinen Sedimenten geeignet ist. Kapitel 4.4 vergleicht und begutachtet die große Anzahl und Vielfalt hydrologischer, biogeochemischer und ökologischer Tracer einschließlich Resazurin. Die physikalische Umwelt (Sedimentmatrix) kontrolliert wie stark die Auswirkungen der Bioturbation auf die Respiration des Sedimentes sind. Dementsprechend liefert diese Doktorarbeit die Basis für das Verständnis der Auswirkungen benthischer Bioturbation auf Respiration und Kohlenstoffumsatz in limnischen und marinen Sedimenten.
Ecosystem engineers are organisms, whose impact on ecosystem functioning is disproportionally large compared to their abundance and biomass. A classic example of ecosystem engineers are burrowing organisms whose activities (bioturbation) affect the sediment matrix and pore solutes in aquatic sediments. Bioturbating animals are impacting on a number of biogeochemical processes in benthic ecosystems, including, among others, aerobic respiration. Respiration of aquatic sediments often comprises over 50% of the total respiration of aquatic systems, and plays a tremendous role in the global carbon cycle. The present thesis deals with the impacts of the physical environment (sediment characteristics, mainly hydraulic conductivity and grain fractions) on the (microbial) respiration of bioturbated sediments. In order to disentangle the effects of bioturbation on respiration, a novel measurement method has been developed (Chapter 4.1). Chapter 4.2 reveals that the impact of bioturbation on sediment respiration increases with increasing temperature. Chapter 4.3 shows that resazurin can also be used for the measurement of respiration in bioirrigated marine sediments. Chapter 4.4 reviews the large number and diversity of hydrological, biogeochemical and ecological tracers including resazurin. The present thesis shows that in sediments with low hydraulic conductivity (diffusion-dominated sediments) (Chapters 4.1,4.2) bioturbation is altering sediment respiration to a larger extent than in sediments with high hydraulic conductivity (advection-dominated sediment) (Chapter 4.3). The physical environment (sediment matrix) controls the intensity of the impacts of bioturbation on sediment respiration. Thus, this thesis provides a basis for understanding the impact of benthic bioturbators on respiration and carbon sequestering in freshwater and marine sediments.

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16

Yee, Karen Ann. "Littoral benthic macroinvertebrate community dynamics in five eutrophic hardwater lakes in north-central Alberta and the influence of Ca(OH)¦2 applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21229.pdf.

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17

Sachse, René. "Influence of climate change on lake ecosystems - disentangling physical, chemical and biological interactions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-167312.

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Climate change affects lake ecosystems in many ways by direct and indirect temperature impacts on hydrophysical structure, hydrology, chemical cycles and on biological interactions. The identification of these climate signals can be complicated and superimposed by other environmental changes, such as land use changes. The aim of this thesis was to seperate temperature effects from effects of management and other environmental influences and to understand the underlying complex processes causing significant changes of ecosystem states. This understanding is important for decisions of lake and reservoir managers to counteract unfavorable consequences of climate change. For the recent study, long-term data of meteorological, hydrophysical and biological variables (phytoplankton, crustacean zooplankton, fish) of the German drinking water reservoir Saidenbach were analysed. Based on this long-term data set, strong indicators for climate induced changes have been identified. In particular, increasing water temperatures since 1975, earlier break up of ice covers and an altered hydrophysical structure could be detected. Thereby, stratification stability increased and turbulent mixing decreased in summer. The water of the reservoir warmed more than the tributaries resulting in a trend to deeper entrainment of the inflows. As further indicators of climate change, an increased annual biomass of phytoplankton and species shifts in the phytoplankton community in spring and summer had been observed. During the spring mass development, the diatom Aulacoseira subarctica became dominant in recent years with warm winters and early ice-out. Its unusual spatial pattern with occurrences in aphotic depths could be explained by easier resuspension compared to other diatoms. By being resuspended first and establishing a high inoculum, A. subarctica profits from an earlier ice-out and earlier full circulation. In spite of a reduced nutrient loading to the epilimnion, in summer, the diatom Fragilaria crotonensis was displaced increasingly by cyanobacteria. This species shift could be explained well by the hydrophysical regime shift. Although, the annual total phytoplankton biomass increased since 1990, the crustacean zooplankton in Saidenbach reservoir did not seem to profit from improved food resources. To the contrary, Daphnia abundances reduced tremendously. We could show that the influcence of fish stocks were underestimated. The stocked silvercarp may have contributed up to 70 % of the total zooplanktivorous fish biomass which had a temperature and density dependent effect. The faster growth of Daphnia at higher temperatures could not compensate for the more actively grazing fish when stock of zooplankitvorous fish was too high. Still, temperature was identified as the most important factor that explained 29 % of the zooplankton phenology, while the second most important predictors were zooplanktivorous fish biomass and nutrient loading, explaining 18 % of the variance. The importance of submerged macrophytes in shallow lakes is well investigated. To increase also the understanding of their impact and their role during climate change on water quality in deep lakes, a model for stratified lakes that includes submerged macrophytes was developed. The simulations showed that macrophyte effects were mainly positive for water quality and macrophytes in deep lakes were able to potentially reduce summer phytoplankton, especially cyanobacteria by 50 % in 11 m deep and still by 15 % in 100 m deep oligotrophic lakes. Nutrient competition with phytoplankton contributed most to this macrophyte effect. In conclusion, for deep lake restoration the re-establishment of submerged macrophytes might be as important as for shallow lakes. The full lake model includes hydrophysical and ecological submodules and thus will allow further comprehensive climate simulations and the evaluation of the effectivity of adaptive strategies and scenarios for deep lakes and reservoirs
Der Klimawandel beeinflusst Seeökosysteme vielfältig durch direkte und indirekte Temperatureffekte auf die hydrophysikalische Struktur, die Hydrologie, chemische Kreisläufe und biologische Interaktionen. Die Identifikation von Klimasignalen kann durch Landnutzungs- und weitere Umweltveränderungen überlagert werden. Ziel dieser Arbeit war es, Temperatureffekte von Effekten zu unterscheiden, die durch Gewässermanagement oder anderen Umweltveränderungen verursacht werden. Weiterhin sollten komplexe Prozesse verstanden werden, die zu signifikanten Veränderungen in Seeökosystemen führen. Dieses Verständnis ist für Talsperren- und Gewässermanager von besonderer Bedeutung, um ungewünschten Folgen des Klimawandels entgegenwirken zu können. Für die Studie wurden Langzeitdaten für meteorologische, hydrophysikalische und biologische Variablen (Phytoplankton, Crustaceen-Zooplankton, Fischbesatz) der Talsperre Saidenbach ausgewertet. Mehrere Indikatoren für die Auswirkungen des Klimawandels konnten basierend auf diesen Daten identifiziert werden. Diese gehören insbesondere eine Erhöhung der Wassertemperatur seit 1975, zeitigere Eisaufbrüche und eine veränderte Schichtungsstruktur. Dabei wurde im Sommer die Schichtungsstabilität höher und die Intensität der Durchmischung geringer. Das Wasser in der Talsperre erwärmte sich stärker als die Zuflüsse, wodurch diese sich zunehmend tiefer und unterhalb der Thermokline einschichten. Eine zunehmende jährliche Phytoplanktonbiomasse und Artenwechsel innerhalb der Planktongemeinschaft sind weitere Indikatoren für Klimafolgen. Die Kieselalge Aulacoseira subarctica erlangte in Jahren mit warmen Wintern und zeitigen Eisaufbrüchen eine Dominanz während der Frühjahrsentwicklung. Das ungewöhnliche Auftreten dieser Art in aphotischen Tiefen konnte durch eine leichtere Resuspension im Vergleich zu anderen Kieselalgen erklärt werden. Durch zeitige Resuspension gleich nach Eisaufbruch kann A. subarctica ein hohes Inokulum etablieren. Trotz reduzierter Nährstoffzufuhr ins Epilimnion wurde im Sommer die Kieselalge Fragilaria crotonensis vermehrt durch Cyanobakterien verdrängt, was jedoch gut mit den Änderungen der hydrophysikalischen Struktur erklärt werden kann. Obwohl seit 1990 insgesamt mehr Phytoplankton zur Verfügung steht konnte das Crustaceen- Zooplankton in der Talsperre Saidenbach nicht von diesen verbesserten Nahrungsbedingungen profitieren. Die Daphnia-Abundanzen waren seit 1990 stark verringert. Es konnte gezeigt werden, dass der Einfluss des Fischbesatzes unterschätzt wurde und die künstlich ins System eingebrachten Silberkarpfen zeitweise bis zu 70% der zooplanktivoren Fischbiomasse ausgemacht haben. Zoo- planktivore Fische haben einen temperatur- und dichteabhängigen Effekt auf das Zooplankton. Das schnellere Populationswachstum von Daphnia kann bei hohem Besatz mit zooplanktivoren Fischen nicht die erhöhte Fraßaktivität der Fische ausgleichen. Dennoch konnte Temperatur als der wichtigste Einflussfaktor auf die Phänologie des Zooplanktons identifiziert werden, gefolgt von zooplanktivorem Fisch und Nährstoffzufuhr. Die Wichtigkeit von submersen Makrophyten in Flachseen ist gut untersucht. Um den Einfluss von Makropyhten auf die Wasserqualität während des Klimawandels auch in tiefen Seen abschätzen zu können, wurde ein komplexes Seemodell entwickelt. Die Simulationen zeigen, dass sich Makrophyten hauptsächlich positiv auf die Wassergüte auswirken und zur Reduktion von Phytoplankton, insbesondere von Cyanobakterien im Sommer, beitragen. In einem 11 m tiefen See betrug die Reduktion 50 %, in 100 m tiefen oligotrophen Seen immer noch 15 %. Die Konkurrenz um Nährstoffe mit dem Phytoplankton war dabei die ursächliche Makrophyten-Plankton-Interaktion. Submerse Makrophyten könnten für die Restaurierung von tiefen Seen folglich genauso wichtig sein, wie für Flachseen. Das komplette Seemodell enthält hydrophysikalische und ökologische Module und ermöglicht damit weitere umfassende Simulationen zur Untersuchung der Auswirkungen des Klimawandels und zur Evaluation von Adaptionsstrategien für Seen und Talsperren

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18

Lindström, Martin. "Predictive Modelling of Heavy Metals in Urban Lakes." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-530.

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Heavy metals are well-known environmental pollutants. In this thesis predictive models for heavy metals in urban lakes are discussed and new models presented. The base of predictive modelling is empirical data from field investigations of many ecosystems covering a wide range of ecosystem characteristics. Predictive models focus on the variabilities among lakes and processes controlling the major metal fluxes.

Sediment and water data for this study were collected from ten small lakes in the Stockholm area, the Eastern parts of Lake Mälaren, the innermost areas of the Stockholm archipelago and from literature studies. By correlating calculated metal loads to the land use of the catchment areas (describing urban and natural land use), the influences of the local urban status on the metal load could be evaluated. Copper was most influenced by the urban status and less by the regional background. The opposite pattern was shown for cadmium, nickel and zinc (and mercury). Lead and chromium were in-between these groups.

It was shown that the metal load from the City of Stockholm is considerable. There is a 5-fold increase in sediment deposition of cadmium, copper, mercury and lead in the central areas of Stockholm compared to surrounding areas.

The results also include a model for the lake characteristic concentration of suspended particulate matter (SPM), and new methods for empirical model testing. The results indicate that the traditional distribution (or partition) coefficient K_d (L kg^-1) is unsuitable to use in modelling of the particle association of metals. Instead the particulate fraction, PF (-), defined as the ratio of the particulate associated concentration to the total concentration, is recommended. K_d is affected by spurious correlations due to the definition of K_d as a ratio including SPM and also secondary spurious correlations with many variables correlated to SPM. It was also shown that K_d has a larger inherent within-system variability than PF. This is important in modelling.

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19

Michalková, Monika. "Human influences on floodplain lake sedimentation." Lyon 3, 2010. http://www.theses.fr/2010LYO31027.

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L'érosion latérale du fleuve Sacramento, Californie: les influences humaines et les conséquences sur l'habitat des lônes L'étude est basée sur l'analyse spatiale et temporelle d'un chenal actif et des lônes associées. On a utilisé une série de photographies aériennes (prises en 1942, 1962, 1985 et 1999) représentant plus de 140 km de longueur. Les changements planimétriques ont été analysés longitudinalement (analyse synchronique) et temporellement (analyse diachronique) pour souligner les structures spatiales et leur évolution temporelle. La révitalisation du Haut Rhône et les premiers résultats de la sédimentation dans les lônes : Des travaux de revitalisation sur le Rhône ont été réalisés en Chautagne, en Belley et Brégnier-Cordon. L'étude des formes et des processus permet d'en évaluer la sédimentation. On considère notamment les trois points suivants: i) la définition du nombre de connexions par an (la fréquence de connexion débordante); ii) les mesures des taux de sédimentation; iii) les analyses statistiques des relations et l'analyse intra-bras (caractérisant les fréquences de connexion et définissant l'espérance de vie des bras morts). Les différents groupes ont été définis par des analyses en composantes principales normées (ACPn). Morphodynamic de la sortie du cut-off méandre: l'analyse expérimentale du terrain et d'études en laboratoire Les expérimentations sur l'évolution morphodynamique à l'embouchure aval d'un bras mort connecté par l'aval et pas par l'amont ont été menées sur un modèle physique de méandres recoupés de la Morava, au VUVH à Bratislava. Les fonnes d'écoulement et de dépôt/érosion pour deux géométries contrastées d'embouchure aval ont été observées, mesurées et simulées par modélisation hydrosédimentaire 2D
Lateral Erosion of the Sacramento River, California: Human influences and consequences for floodplain lake habitats This study is based on a spatial and temporal analysis of the active channel and associated flood plain lakes using aerial photographs spanning five decades (1942, 1962, 1985, 1999) over the entire 140 km long reach. Planimetric changes were analysed longitudinally (synchronic analysis) and temporally (diachronic) to highlight the spatial structures and their evolution through time. Revitalisation of Ht. Rhône and First Feedbacks on Revitalised Floodplain Lakes Sedimentation along the Rhône River The revitalisation work on Rhône River has been done on three different localities: Chautagne, Belley and Brégnier-Cordon. The morphologic form as a result of processes become consequently the control factor. Three steps were considered: i) to define the number connexions by year (the frequency of overbank connexion) ; ii) the measurement 1 of the sedimentation rates iii) the statistical analysis of the relationships and inter-lake analysis (the characterise of connexion frequency and to define the life expectancy of floodplain lakes). The diffèrent groups were defined by nPCA analysis. Morphodynamics of the Exit of a Cut-off Meander: Experimental Findings from Field and Labora tory Studies The morphological evolution of the entrances and exits of abandoned river channels govems their hydrological connectivity. The study focusses on flow and sediment dynamics in the exit of a cut-off meander where the downstream entrance Îs still connected to the main channel, but the upstream entrance is closed. Two similar field and laboratory cases were investigated using innovative velocimetry techniques (acoustic Doppler profiling, image analysis). Laboratory experiments were conducted with a mobile-bed physical model of the Morava river (Slovakia). Field measurements were performed in the exit of the Port-Galland cut-offmeander, Ain river (France)

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20

Russell, Victoria Louise. "Nutrients versus habitat structure : influences on biodiversity in shallow freshwater lakes." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402360.

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21

Wällstedt, Teresia. "Influence of acidification and liming on metals in lake sediments." Doctoral thesis, Stockholm University, Department of Applied Environmental Science (ITM), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-471.

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Emission and precipitation of acidifying substances and metals has caused severe acidification and increased metal concentrations in lakes and streams in Sweden as well as many other countries during the last decades. To counteract the negative effects of acidification, liming has been used extensively in Sweden since the 1970’s, a treatment that has been called one of the largest man-maid manipulations of aquatic ecosystems ever.

The aim of this thesis is to investigate the influence of acidification and liming on deposition of metals to lake sediments, and to look at the fate of metals in sediments during a possible reacidification process because of terminated liming.

Studies of both surface sediments and dated sediment profiles sampled from limed lakes and non-limed reference lakes indicated that liming causes increased sedimentation of many metals. Increased deposition to the sediments was found for Al, Cd, Co, Ni, Fe, Mn and Zn, probably as a direct result of the increased pH. Liming was also found to increase the deposition of As and Cr, but that was probably due to the secondary effect of association to Fe and Mn complexes. No influence of lime treatment on the deposition of Hg, Pb and V to lake sediments could be demonstrated. The studies also indicated that acidification can decrease the deposition of Cd, Fe, Mn and possibly also Co and Zn to the sediments.

The contribution from the used lime products to the metal load in sediments of lakes limed directly on the lake surface was also evaluated. The lime products were found to be an important source for Al, Cu and Ni and a relatively important source for Co, Cr, Hg and V, but did not seem to contribute much to the content of As, Cd, Pb or Zn in lake sediments.

An experimental study of reacidification showed that (re)mobilisation of metals, e.g Al, Cd, Mn and Zn, from sediments may occur and that reacidification of formerly lime treated lakes may contribute to increased concentrations of these metals in the lake water. Cu, Fe and Pb are less affected by pH changes and the concentrations of these metals will probably not increase in lake water during reacidification.

Altogether, the thesis shows that lime treatment causes increased deposition of many metals to the lake sediments, whereas reacidification may lead to remobilisation of some metals from the sediments with increased concentrations in the water phase as a result.

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22

Wällstedt, Teresia. "Influence of acidification and liming on metals in lake sediments /." Stockholm : Dept. of Applied Environmental Science, Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-471.

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23

Clark, Andrew J. "Lake Erie Holocene Coastal Evolution near the Portage River-Catawba Island, Ohio." Bowling Green State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1211323047.

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24

Schaefer, Robert T. "Evaluating the Influences of Karst Hydrogeology on Freshwater Harmful Algal Blooms in Kentucky Lakes." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1619.

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A problem exists in Nolin River Lake and Rough River Lake in Kentucky, due to the increasing prevalence of cyanobacterial-based harmful algal blooms (CyanoHABs) and the threats they pose to local communities. These lakes were developed as artificial reservoirs from embankment. Further complicating the issue, the lakes are located within a heavily karstified region and there exists no plan or method currently for monitoring or managing CyanoHABs in a karst region with regard to groundwater inputs to the lake systems or their tributaries. A mixture of techniques and analysis methods was used to determine the best way to monitor and possibly detect the formation and occurrence of CyanoHABs in artificial lakes that are located in karst landscapes. The methods focused on determining the effect groundwater has on CyanoHAB occurrence and formation, how much nutrient pollution is entering the system, from where the pollution is originating and, ultimately, how best to monitor and develop management practices against CyanoHAB occurrence. Techniques used included dual nitrate isotope tracing, collecting hydrogeochemical data, lake discharge data, historical CyanoHAB data, and biological tracer monitoring in both lakes. The lakes under study showed varying degrees of the influence karst plays in their seasonal changes from summer to winter pools. Lake water temperatures never dropped below the temperatures needed for one of the dominant cyanobacteria, Cylindrospermopsis raciborskii, to grow. Calculations of nutrient loadings indicated that over 3.5 x 106 kg of nitrate moved through Nolin River Lake during the course of the study. The presence and concentrations of E. coli when paired with weather and geochemical data also revealed karst groundwater pulses exerting an influence through the system in response to precipitation events. The nitrogen and oxygen isotope data indicate that a wide variety of nitrate pollution sources are entering the system and that a variety of management techniques must be deployed to combat this complex issue. A holistic approach that focuses on management and education about karst processes and CyanoHABs is suggested, with an emphasis on broader community involvement beyond just the populations living adjacent to the lakes.

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25

Egli, Ramon. "Environmental influences on the magnetic properties of lake sediments." Zürich : [s.n.], 2003. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15090.

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26

Smith, Dian H. "Influence of Sediment Exposure and Water Depth on Torpedograss Invasion of Lake Okeechobee, Florida." Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5607/.

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Torpedograss (Panicum repens) was first observed in Lake Okeechobee in the 1970s and appears to have displaced an estimated 6,400 ha of native plants, such as spikerush (Eleocharis cellulosa), where inundation depths are often less than 50 cm. Two series of studies evaluated substrate exposure and water depth influences on torpedograss establishment and competitiveness. Results revealed that fragments remain buoyant for extended periods and so facilitate dispersal. Once anchored to exposed substrate fragments can readily root and establish. Subsequently, torpedograss thrives when subjected to inundations to 75 cm and survives prolonged exposure to depths greater than 1 m. These findings suggest that fluctuating water levels contribute to torpedograss dispersal and colonization patterns and that low water levels increase marsh area susceptible to invasion. The competition study found that spikerush grown in monoculture produces significantly more biomass when continually inundated to shallow depths (10 to 20 cm) than when subjected to drier conditions (-25 cm) or greater inundations (80 cm). In contrast, torpedograss establishes more readily on exposed substrate (-25 to 0 cm) compared to inundate substrates. During the first growing season biomass production increases as substrate exposure interval increases. However, during the second year, established torpedograss produces more biomass when grown on intermittently wet (0 cm) compared to permanently dry (-25 cm) or intermittently inundated (10 cm) substrates. No difference in production was observed between substrates permanently inundated (10 cm) and any other regime tested. During the first two years of torpedograss invasion, regardless of treatment, spikerush suppresses invasion and torpedograss had little effect on established spikerush, indicating that spikerush-dominated areas are capable of resisting torpedograss invasion. Even so, disturbances that might cause mortality of long hydroperiod species, such as spikerush, may create open gaps in the native vegetation and thus facilitate torpedograss establishment and expansion.

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27

Bollmer, Kathleen A. "The Influence of Balanced Growth in the Ohio Lake Erie Watershed." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258654351.

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28

Franks, Jessica L. "Spatial and Temporal Influences of Water Quality on Zooplankton in Lake Texoma." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2532/.

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Seventy-one aquatic species including the copepodids and nauplii were identified from Lake Texoma from August 1996 to September 1997. Zooplankton community structure, abundance and spatial and temporal distributions were compared among five lake zones delineated a priori based on chloride concentration. The zones, in order of decreasing chloride concentration, are the Red River zone (RRZ), Red river Transition zone (RRTZ), Main Lake zone (MLZ), Washita River Transition zone (WRTZ) and Washita River zone (WRZ). Bray Curtis Similarity Index showed community structure was most similar in the two Red River arm zones, the two Washita River arm zones and the MLZ. Zooplankton abundance was greatest in the Red River arm (312 org/L), intermediate in the Washita River arm (217 org/L) and least in the Main Lake body (103 org/L). A significant increase in the abundance of a deformed rotifer, Keratella cochlearis, was observed mainly in the Red River arm during a second study from March 1999 to June 1999. Seasonal dynamics, rather than spatial dynamics, were more important in structuring the zooplankton community, especially in the two river arms. Spatial variance was solely attributed to station and zone effects independent of time for a few crustacean species and many of the water quality parameters supporting the presence of longitudinal gradients of differing water quality. Three independent models (Red River arm, Washita River arm, Main Lake body) rather than a single model for the entire reservoir, best describe patterns in the zooplankton community and its relationship to seasonal, physical and chemical factors. Statistical power, sample size and taxonomic resolution were examined. When monitoring seasonal and annuals trends in abundance, the greatest statistical power was achieved by analyzing count data at taxonomic levels above genus. Taxonomic sufficiency was assessed to determine if costs could be reduced for zooplankton identifications. For water quality monitoring purposes only, it is recommended that genus identifications are sufficient if supplemented with quarterly species identifications.

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29

Rydell, Joseph J. "The influence of abiotic factors on gill-net catch rates and the evaluation of mortality rates for yellow perch in southern Lake Michigan." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1391675.

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I determined differences in yellow perch gill-net catch-per-unit-effort (CPUE) at two depths (10 and 15 m) in the Indiana waters of Lake Michigan during June, July, and August from 1989 to 2006. I evaluated the abiotic factors of water temperature, water clarity, wave height, and wind direction to determine whether they influence the differences in yellow perch CPUE. This study suggests that yellow perch in southern Lake Michigan may select habitat based on water temperature during the summer, moving in response to thermocline changes. We also evaluated mortality rates for two distinct periods (1984-1994 and 2000-2007) in order to identify the response of the population to changes in exploitation. Yellow perch during 1984-1994 (high exploitation) and 2000-2007 (low exploitation) displayed an increase in mortality for fish of harvestable size. In addition, during 2000-2007 (low exploitation) we identified that female yellow perch reached exploitable size earlier in life than males.
Department of Biology

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30

Powell, Floyd Alma. "Influence of Boat Density Levels on Boaters' Satisfaction at Hyrum Lake, Utah." DigitalCommons@USU, 1998. https://digitalcommons.usu.edu/etd/4429.

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The purpose of this study was to evaluate the effects of boat density on boaters' satisfaction at Hyrum Lake State Park, Utah. The study evaluated relationships between boaters' satisfaction with their Hyrum Lake experience and density of boats at different locations on the lake and among participants in different boating activities. The participants in this study were boaters who used Hyrum Lake between May and September of 1996. An oral, onsite interview survey was randomly given to 282 boaters as they left the lake for the day. The surveys were conducted on high-density days (weekends) and low-density days (weekdays) , which were also randomly selected. Correlation analysis and analysis of variance (ANOVA) were performed . The study found no significant relationships between density and satisfaction associated with either lake location or activity. Satisfaction did not differ between activities; however, participants in two activities (fishing and water skiing) did report higher satisfaction while using the boat ramp than for other locations on the lake. When a Welch t' test was performed comparing boating density ≤ 44 with boating density ≥ 45 boats, even though there was no statistically significant difference, a suggested trend did appear . The results indicate a slightly higher satisfaction rating among water skiers when density was 44 or fewer boats. Conversely, personal watercraft (PWC) users indicated that their satisfaction levels were higher when boating density was ≥ 45 boats. This would suggest that PWC users may be satisfied at boat densities much higher than other users could accept. Although 74% of all the boaters surveyed wanted to set a limit (carrying capacity) on the number of boats allowed on the lake at one time, the carrying capacity will not be immediately implemented, because the data found no statistically significant difference in satisfaction levels with higher boat densities.

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31

Rooney, Neil. "Scale of analysis and the influence of submerged macrophytes on lake processes." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37665.

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The goal of this thesis was to examine submerged macrophoe biomass, distribution, and ecosystem effects at scales large enough to incorporate the littoral zone into models of whole lake structure and function. Submerged macrophyte biomass and distribution was shown to be highly variable between growing seasons and primarily dependant upon air temperature and the timing of the onset of the growing season. Within a growing season, a mass balance study showed an undisturbed macrophyte bed to markedly lower phytoplankton biomass: total phosphorus ratios, although the net effect of the bed on the growing season phosphorus budget was minimal. The weedbed preferentially retained phytoplankton biomass while being a source of bacterial production to the open water. These findings were mirrored at the among lake scale, as planktonic respiration and bacterial production were higher in macrophyte dominated lakes than would be expected based on phytoplankton biomass alone. Further, phytoplankton biomass was lower than would be expected based on epilimnetic phosphorus levels, showing that the classical view of pelagic interactions that proposes phosphorus determines phytoplankton abundance, which in turn determines bacterial abundance through the production of organic carbon, becomes less relevant as macrophyte cover increases. Long term phosphorus accumulation in the littoral zone was shown to be linked to macrophyte biomass, and on average almost an order of magnitude higher than calculated from the growing season (June--October) phosphorus budget, suggesting that the bulk of phosphorus accumulation in weedbeds occurs outside of the growing season. Finally, sediment core data showed that while submerged weedbeds accumulate up to four times as much bulk sediment compared to the profundal zone, phosphorus accumulation in weedbeds is much less than observed in the profundal zone. These results strongly indicating that submerged macrophyte beds play a central role in trapping ep

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32

Brown, Andrea Marcelline. "Shoreline residential development and physical habitat influences on fish density at the lake edge of Lake Joseph, Ontario." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq40883.pdf.

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33

Coleman, Laura L. "Factors that influence post-baccalaureate community college students' choice to attend Lake Michigan College /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3137686.

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34

Pazzia, Ivano. "The influence of food web structure on the growth and bioenergetics of lake trout (Salvelinus namaycush) /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31525.

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Most fish species tend to feed on larger prey as their size increases. The lack of suitable prey during critical periods of their life can prevent them from shifting their diet to larger prey and also from reaching larger body sizes. In this study, we compared the energy budget of lake trout ( Salvelinus namaycush) populations with contrasting food webs. Non-piscivorous lake trout (NPLT) populations reached a much smaller size and grew at a much slower rate than picivorous lake trout (PLT) populations. Food consumption rates were on average, 2--3 times higher in NPLT when they were expressed on a wet weight basis. However, only a slight difference in their energy intake was detected (less than 10%) once consumption rates were corrected for differences in prey caloric content. Growth efficiency was about two times lower in NPLT compared to PLT, while their metabolic costs were higher and assimilation efficiency was lower. It is most likely that the increased metabolic costs were associated with higher foraging costs, since more feeding attempts must be made to acquire a given quantity of food when fish are feeding on smaller prey. Furthermore, the portion of indigestible matter is likely to be higher in the diet of NPLT than in PLT (e.g. chitin versus bone). These results are consistent with theoretical models of fish growth that have showed that lake trout must have access to larger prey, even if they are rare, to reach larger body sizes. Our study also illustrates how the restructuring of a prey community by the arrival of an exotic species into a food web could alter the growth rate of a top predator. Furthermore, our study suggests that age at first maturity is influenced by growth efficiency in indigenous populations of fish. Therefore, the dynamic of a population and its vulnerability to exploitation are likely to be influenced by their energy allocation strategy.

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35

Koçer, Zeynep A. "Detection of Influenza A Viruses From Environmental Lake and Pond Ice." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1276804585.

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36

Ara, Shihomi. "The influence of water quality on the demand for residential development around Lake Erie." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1184599591.

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37

Fowler, Joshua K. "Influence of Lake Levels and Ice Cover on a Modified Shoreline: Ohio’s Headland Beaches." Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1433415129.

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38

Roskosch, Andrea. "The influence of macrozoobenthos in lake sediments on hydrodynamic transport processes and biogeochemical impacts." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16423.

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Ziel dieser Dissertation ist, Wissensdefizite im Bereich der Bioirrigation von Süßwassersedimenten abzubauen. Als Untersuchungsorganismus wurde Chironomus plumosus ausgewählt weil diese weit verbreitete Larve ihre U-förmigen Röhren mit Überstandswasser durchspült und so Nahrung aus dem Wasser filtriert. Um Bioirrigation in Wohnröhren mit einem Durchmesser von ca. 1,7 mm zu untersuchen, wurden geeignete Messmethoden entwickelt, mit denen für das 4. Larvenstadium die Parameter Fließgeschwindigkeit (14,9 mm/s), Pumpzeit (33 min/h) und Pumprate (61 ml/h) gemessen wurden. Bei einer Populationsdichte von 745 Larven/m2 kann somit ein Wasservolumen äquivalent zum Volumen des Müggelsee in Berlin, innerhalb von 5 Tagen durch das Sediment gepumpt werden. Die Positronen-Emissions-Tomographie wurde für die Sedimentanalytik adaptiert und der Transport im Porenwasser analysiert. Mit den Untersuchungen wure gezeigt, dass auch in schlammigen Seesedimenten ein advektiver Transport durch Bioirrigation verursacht wird, der nicht zu vernachlässigen ist. Steigende Temperaturen resultieren aufgrund steigender Fließgeschwindigkeit in einen signifikanten Anstieg der Pumprate sowie der Eintragsrate von Überstandswasser ins Sediment. Ein abfallender Sauerstoffgehalt verlängert die Pumpzeit und führt zu einer sinkenden Fließgeschwindigkeit. Außerdem wird aus den Untersuchungen eine jahreszeitliche Variabilität der Bioirrigation sichtbar, welche unabhängig von konstanten Laborbedingungen auftritt. Mit dem Wasserstrom werden Porenwasserspezies wie SRP in den Wasserkörper abtransportiert, wohingegen SO42- und O2 aus dem Überstandswasser in das Sediment eingetragen werden. Ferner kommt es zur Oxidation von Fe2+ infolgedessen Phosphat im Sediment festgelegt wird, wie mittels P-Fraktionierung gezeigt werden konnte. Mikrobiologische Untersuchungen zeigten, dass Bioirrigation die mikrobielle Abundanz steigert, die Bakteriengemeinschaft verändert und das Potential zur enzymatischen Hydrolyse erhöht.
The aim of this thesis is to fill gaps of knowledge regarding bioirrigation in freshwater sediments. Chironomus plumosus was chosen for the investigations since the filter-feeding larva dwelling in U-shaped burrows is quite common and flushes its burrow with water from the overlying water body. To investigate bioirrigation activity in burrows of approximately 1.7 mm in diameter appropriate measurement techniques were developed. With the methods several parameters were measured for 4th stage of larvae: flow velocity (14.9 mm s-1), pumping time (33 min h-1), and pumping rate (61 ml h-1). Consequently, a water volume equivalent to the volume of Lake Müggelsee in Berlin is pumped through the sediment every 5 days by a population density of 745 larvae m-2. The nuclear medicine imaging technique Positron Emissions Tomography was adapted and used to analyze the transport in the sediment pore water. By means of the experiments, it could be shown that even in muddy lake sediments advection is a relevant transport process and should not be neglected. Rising temperatures result in increased pumping rates and increased influx rates of surface water into the sediment due to increased flow velocities in the burrows. Dropping oxygen concentrations prolong the pumping duration while the flow velocity decreases. Furthermore, experiments show a seasonal variability of bioirrigation which is independent of constant laboratory conditions. Pore water species such as SRP are transported with the water flow into the overlying water body, whereas SO42- and O2 are transported from the overlying water into the sediment. Due to the oxidation of Fe2+, phosphorus is fixed into the sediment, a result confirmed by P-fractionation. Microbiological investigations of the burrow walls demonstrated that the bioirrigation activity enhances the microbial abundance, changes the community structure, and increases the potential of enzymatic hydrolysis.

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39

Brunkalla, Roberta Joann. "Influence of Mixing and Buoyancy on Competition Between Cyanobacteria Species in Upper Klamath Lake." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3998.

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Cyanobacterial blooms in lakes impact human health, the economy, and ecosystem health. It is predicted that climate change will promote and increase the frequency and intensity of cyanobacterial blooms due to unique physiological adaptions that allow cyanobacteria to exploit warm stable water bodies. Key cyanobacteria physiological adaptions include nitrogen fixation, buoyancy regulation and higher optimum growth temperatures. The largest uncertainty of predicting the effect of climate change is in understanding how the interactions among species will change. Adding to the ambiguity, cyanobacteria physiological adaptions can vary based on lakespecific ecotypes and can have different sensitivities to temperature. It is critical to understand how cyanobacterial physiological adaptions impact species interactions in order to improve and devise adaptable, short‐term management methods for bloom control. This study investigated how weather patterns and algal buoyancy regulation influence the competition and accumulation of two bloom‐forming buoyant cyanobacteria species (Aphanizomenon flos‐aquae (APFA) and toxin‐forming Microcystis aeruginosa (MSAE)) in Upper Klamath Lake (UKL), Oregon. The focus was confirming the buoyancy rate of the APFA in Upper Klamath Lake and exploring whether short‐term weather conditions could lead to dangerous accumulations of APFA or MSAE. A sensitivity analysis was conducted on the model's buoyancy terms and growth curves to see if the outcome of competition was influenced by these parameters. UKL specific buoyancy rates were measured on APFA from samples taken directly from the lake in the summer of 2015. Tracking software was used to measure APFA movement through water, and individual colony movement was averaged to obtain a single buoyancy rate. There was a high degree of agreement between the calculated APFA buoyancy rate in UKL (0.89 ± 0.34 m hr-1) with the rate published by Walsby (1995; 0.9 ± 0.5 m hr-1). This study investigated how weather patterns and buoyancy regulation influenced the outcome of competition between APFA and MSAE. Weather and water column temperature data were collected from UKL in the summer of 2016. A onedimensional hydrodynamic model was used to calculate the lake's thermal and turbulence structure on days with contrasting weather patterns (hot/cool and windy/calm). A competition model was used to calculate the accumulation of APFA and MSAE cells in regular intervals through the water column under the various weather scenarios. MSAE accumulation was significantly influenced by the thermal and turbulence regimes, but APFA maintained high accumulations under every regime and was the better competitor under every thermal and turbulence regime. MSAE was more negatively impacted by high turbulence than low temperatures. APFA's optimum temperature growth curve was found to be important in determining the outcome of competition between APFA and MSAE. Surprisingly, competition was not sensitive to changes in buoyancy rates. Buoyancy was not found to be a function of algal accumulation under any thermal and turbulence regime. The impacts of climate change and human‐induced enrichment has the potential to change existing patterns of species interactions in lentic systems. Restoration and management efforts should consider the significance of cascading ecological responses to climate change. Understanding how key physiological adaptions operate is the first step to assessing the scope of this impact. While buoyancy might not play a large role in competition in UKL, it might be possible to use mixing to suppress MSAE because it is negatively impacted by high turbulence. If MSAE hot spots become a reoccurring problem in UKL, lakes managers might be able to use localized mixing to suppress MSAE blooms in these problem areas.

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40

Hoar, Cara Chowning. "Fish response to discharge events from a power plant cooling reservoir in a river affected by acid mine drainage and thermal influences." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4204.

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Thesis (M.S.)--West Virginia University, 2005.
Title from document title page. Document formatted into pages; contains viii, 70 p. : ill., maps. Vita. Includes abstract. Includes bibliographical references.

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41

Mockutė, Renata. "Šiaulių senamiesčio įtakos zonos, prie Talkšos ežero, architektūrinė - urbanistinė koncepcija." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110622_154850-59937.

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Ilgą laiką Šiaulių miestas neturėjo aiškiai išskirtų vertingiausių saugomų struktūrinių zonų. Ši problema paliko neigiamus pėdsakus miesto morfologijai. Istorinėje miesto dalyje - prieigose atsiradę per dideli sklypai lėmė struktūrinių anomalijų atsiradimą. Ypač didelė problema tapo apleistas pramoninis kompleksas gamtinio karkaso ruože, prie Talkšos ežero, - nenuoseklios miesto plėtros pasekmė. Baigiamojo darbo tikslas- pervertinus Šiaulių senamiesčio ir jo prieigų struktūrą, numatyti struktūrines ribas, sudaryti planavimo veiklos reglamentą, planavimo principus. Jais remiantis pasiūlyti reikšmingos senamiesčio įtakos zonos, prie Talkšos ežero, architektūrinę - urbanistinę koncepciją. Atlikus išsamius tyrimus mieste, numatytos struktūrinės miesto ribos, planavimo reglamentas. Istorinė, urbanistinė analizė padiktavo teritorijos prie Talkšos ežero koncepciją, apimančią kompleksiško kultūros paveldo vertybių, jų vizualinės apsaugos respektavimo, gatvių tinklo pertvarkymo, reljefo suformavimo, viešųjų erdvių tinklo plėtros galimybes. Darbo rezultatas - Ch. Frenkelio istorinio pramoninio komplekso konversija į kultūros ir mokslo fabriką, remiantis sudarytu užstatymo planavimo reglamentu (Šiaulių senamiesčio įtakos zonoje, prie Talkšos ežero). Darbą sudaro grafinė medžiaga ir tekstinė dalis, įvadas, analitinė -metodinė dalis, tiriamoji - eksperimentinė, išvados, siūlymai, priedai -iliustracijos, lentelės, papildomos grafinės medžiagos... [toliau žr. visą tekstą]
Šiauliai city did not clearly distinguish the most valuable structural protected areas for a long time. This left negative traces of urban morphology. Large quarters occured in the historical part of town and influenced structural anomalies. Particularly big problem was enormous and abandoned industrial complex in delicate natural area neat Talkša lake - inconsistent result of urban development. The main objectives of master thesis are to reappraise Šiauliai old town and infuance zones structure, provide the structural limits, planning regulations, principles. On this basis suggest a significant impact on the old town area, near lake Talkšos, architectural - urbanistic concept. According to studies offer architectural urban conception of Šiauliai old town influence zone near Talkša lake. City investigations presented structural zones and urban planning regulations. Conception of the zone near Talkša lake was dectated by urban and historical analysis. The conception includes an integrated cultural heritage, their visual respectation protection, street network transformation, the formation of relief, public spaces, network development opportunities. The result - Ch. Frenkel historical industrial complex conversion to culture and science factory, according to urban planning regulations ( Šiauliai old town influence zone near Talkša lake) Work consists of graphic and textual material part of the introduction, analytical and... [to full text]

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42

Grahn, Evastina. "Lake sediment as environmental archive : natural and anthropogenic influence on the chronology of trace elements /." Örebro : Örebro universitetsbibliotek, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-372.

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43

Klemmer, Amanda Jeanne. "The influence of stream-derived detritus subsidies on lake benthic community composition and trophic interactions." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36631.

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Cross-ecosystem subsidies are important for the structure and functioning of communities within many ecosystems. Increases in subsidies have been modeled to increase trophic cascade strength within recipient systems, because of the donor-controlled addition of a resource. Streams receive high inputs of detrital subsidies and what is not processed within the system is transported downstream. Therefore, streams that flow into lakes have the potential to provide large amounts of detritus to lakes compared to the transfer of detritus from forested lake edges. I hypothesized that streams would increase detritus standing stocks around stream mouths in lakes, that streams would affect the benthic invertebrate community composition, and that those effects would change with distance from the lake shore. To test this I conducted a survey of detritus standing stocks and benthic invertebrate communities at six stream/lake interface and six forest/lake interface sites within two lakes. I found that streams and distance into lakes affected detritus standing stocks, but the effect was only seen when individual pairings of stream and forest sites were examined. I also found that headwater streams significantly altered invertebrate community composition in the lake littoral zone, even up to a distance of 27 meters into the lakes, with some taxa only found at stream/lake interfaces. These results suggest that streams alter the amount of basal resources through subsidies and contribute to whole lake biodiversity. My second hypothesis was that increased detritus in lakes would increase trophic cascade strength. To test this hypothesis, I conducted an in-lake cage experiment in which I manipulated detritus standing stocks (5 densities) and presence of a top-predator (trout). I found that increasing subsidies altered strength of trophic cascades. But unexpectedly, low detritus treatments experienced the strongest positive effect on algal biomass. At intermediate detritus levels there was a switch in the indirect effects of predators, and at the highest detritus densities predators had a negative indirect effect on algal biomass. These results provide evidence that along a gradient of detritus subsidies, trophic cascade strength experiences threshold responses in where predators may have strong, but opposite indirect effects on primary production.

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44

Morandi, Marc Joseph. "Assessing the Influence of Different Inland Lake Management Strategies on Human-Mediated Invasive Species Spread." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365116997.

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45

Lamb, Cho. "The influence of temperature and metaphyton on non-biting midges (Diptera: Chironomidae) at Lake Joondalup." Thesis, Lamb, Cho (2001) The influence of temperature and metaphyton on non-biting midges (Diptera: Chironomidae) at Lake Joondalup. Honours thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/40787/.

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Problems of nuisance midge (Diptera: Chironomidae) swarms are common at enriched Perth Wetlands. This project sought to investigate the following hypotheses: Environmental parameters are not limiting to larval chironomid density; larval chironomid density is related to environmental temperature; metaphyton provides both a food source and habitat for larval chironomids. The following variables were measured at three sites over the period April to September, 2001: conductivity, pH, gilvin, turbidity, dissolved oxygen, chlorophyll a, total nitrogen, total phosphorus, ambient temperature and temperature of the sediment, water column and metaphyton. The three sampling sites provided contrasting habitats and potential food resources for chironomid larvae: bare sediment with dense stands of the algae Chara sp. and sediment covered by a layer of metaphyton. Larval densities reached 6817 larvae m-2 during the sampling period, however no nuisance swarms were recorded. Of the environmental variables measured, only conductivity, dissolved oxygen and temperature appeared to limit larval chironomid density. Comparison of the ambient temperature for 2000 (when a nuisance swarm occurred) and 2001, suggests that temperature was important for triggering the emergence rates of pupa required for nuisance swarm densities. Food resources were found to be non-limiting to the development of chironomid larvae. Furthermore, the diet of larvae reflected the composition of food resources found at each of the three micro habitats. A mathematical model was constructed to examine the interaction between water column phytoplankton, phosphorus concentrations, temperature and larval chironomid densities. The results obtained suggested that temperature had the greatest influence on larval chironomid densities. Further modifications might include factors such as metaphyton and detritus as food sources.

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46

Chen, Katherine C. (Katherine Cheeyung). "Compositional influences on the microstructures, phase stability, and mechanical properties of TiCr₂ laves phase alloys." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40213.

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47

Mooney, Karen Marie. "The occurrence of cyanobacteria and cyanotoxins in Irish lakes and their relationship with environmental influences and Zebra Mussels Dreissena polymorpha." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546337.

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48

Gatt, Michael Henry. "Mitochondrial DNA diversity and anthropogenic influences in walleye (Stizostedion vitreum) from eastern Lake Huron." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ35891.pdf.

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49

Radl, Viviane. "Influence of trenbolone on the structural and functional diversity of microbial communities from a lake sediment." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978952626.

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50

Spitz, Maya. "The influence of dissolved organic carbon and pH on the photodegradation of methylmercury in lake waters." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26316.

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Photodegradation rates of methylmercury (MeHg) were measured in water samples from several lakes in the Lake Berthelot region in Quebec in order to investigate the impact of drainage basin logging and associated changes in dissolved organic carbon (DOC) concentrations on MeHg levels in lake water. The lakes were selected on the basis of the amount of logging that had previously taken place in the drainage basin, and on DOC levels which were correspondingly higher in logged lakes due to increased runoff. Lakes DA9 and DF9 had DOC concentrations of 12.3 and 20.9 ppm, respectively and were designated as high DOC for the purposes of this study. Lakes N55 and N70 had DOC concentrations of 6.9 and 6.8 ppm, respectively and were designated as low DOC lakes. Experiments were conducted with both ambient and 2 ppt spiked MeHg levels in the high and low DOC lakes to determine whether the spiked levels reflect photodegradation patterns occurring in nature. The effect of different sized DOC fractions on photodegradation rates were also examined. Upon spiking, the binding of added MeHg reached equilibrium virtually immediately (within minutes) for all size fractions. It was hypothesized that less photodegradation of MeHg would be found in high DOC lakes than in low DOC lakes. In contrast to expected results, no photodegradation was observed in the two lower DOC lakes, but there was photodegradation in the two higher DOC lakes. Hypothesizing that larger size fractions of DOC would result in lower methylmercury (MeHg) photodegradation rates, water samples were fractionated into three DOC size fractions (300 kDa, 30 kDa, and 5 kDa). In the two high DOC lakes in which photodegradation was detected, DOC size fractions had an effect on photodegradation rates, though this effect varied. Average k values (hr-1) for DA9 were -1.25 x 10-1 for the 5 kDa fraction, -1.16 x 10 -1 for the 30 kDa fraction, and -9.21 x 10-2 for the 300 kDa fraction, indicating a decrease in photodegradation rates with larger fractions. For DF9, average k values were -1.69 x 10-1 for the 5 kDa fraction, -6.38 x 10-2 for the 30 kDa fraction, and -1.34 x 10-1 for the 300 kDa fraction, which does not indicate a clear trend in photodegradation rates with respect to DOC size fraction. A comparison of samples from a wetland outflow using ambient MeHg levels demonstrated that 300 kDa DOC fractions showed no photodegradation while 5 kDa DOC showed photodegradation with a k value of -9.12 x 10-2 (hr-1). Overall, watershed logging status was found not to affect MeHg photodegradation rates in the lakes studied. A possible contributor to the variation in photodegradation rates between lakes was postulated to be pH, with H+ ions displacing MeHg from binding sites on DOC and rendering it available for photodegradation. To study the relationship between rates of photodegradation and pH, water samples were adjusted to pH values of approximately 4.5, 6.5, and 7.5 and incubated in sunlight. Rates of photodegradation increased with decreasing pH conditions in all lakes, except for one lake (N55) which also had no detectable photodegradation during the initial field trials. In the remaining three lakes studied, however, lower pH values (4.1-4.6) resulted in greater photodegradation than higher pH values that resulted in little or no photodegradation. It appears that this effect only occurs in lakes with a potential for photodegradation. As results suggested that the size of DOC controls rates of photodegradation, samples were analyzed for the size of DOC and corresponding MeHg content using tangential flow ultrafiltration (TFUF). The efficacy of the TFUF system as a means of both removing microbes as well as fractionating DOC into differing size fractions was evaluated. Results indicated that this is an effective field-portable method. Mass balances for MeHg recovery after filtering large volumes of water were found to be 96% for the 5 kDa filter, 81% for the 30 kDa filter, and 109% for the 300 kDa filter, while flow rates decreased by 26%, 17%, and 50% respectively. Potential artifacts of DOC fractionation using the TFUF were investigated. The amount of DOC passing through the filter was found to decrease with increasing volume of filtrate that passed through the membrane.

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