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One of today's major environmental issues is algal blooms linked to eutrophication of lakes and oceans. That is a result of anthropogenic influence with nutrient loads (including phosphorus) from agriculture and industry, which benefits primary production (phytoplankton). Studies have shown that phosphorus availability in the water column can be limited by liming, therefore could be a way to counteract eutrophication. This was tested in the agriculturally surrounded lake Tåkern in southern Sweden, which in its present state is an internationally important bird lake and therefore in several respects would be affected by eutrophication. The purpose of this study was to investigate whether liming would be a good solution to solve any future eutrophication problems in Lake Tåkern. Liming experiments were performed in mesocosms during April 2015 with a mixture of limestone and slaked lime. Quantity and diversity of plankton and water chemical variables were measured before and after liming. Moreover, samples of phytoplankton from a similar experiment conducted in July 2014 were analyzed. Liming did not show any effect on neither phyto- nor zooplankton when performed in spring of 2015. During summer of 2014, there was an increase in number of phytoplankton (ml-1 ) and chlorophyll in controls while the study showed constant levels in treated mesocosms. For zooplankton there was no significant effects of liming on neither quantity nor diversity. Results of this study suggest that liming is not the most appropriate method to resolve eutrophication in Lake Tåkern.

by Tam, Pui Fun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 147-166). / Abstract also in Chinese. / List of Tables --- p.i / List of Figures --- p.ii / List of Plates --- p.v / Acknowledgements --- p.vi / Abstract (in English) --- p.vii / Abstract (in Chinese) --- p.ix / Chapter Chapter 1. --- General introduction --- p.1 / Chapter Chapter 2. --- Temporal and spatial distribution of Copepoda in the Zhujiang River estuary --- p.3 / Chapter 2.1 --- Literature review --- p.3 / Chapter 2.1.1 --- Physical properties of estuaries --- p.3 / Chapter 2.1.2 --- Factors affecting the zooplankton community --- p.4 / Chapter 2.1.2.1 --- Temperature --- p.4 / Chapter 2.1.2.2 --- River discharge and salinity --- p.5 / Chapter 2.1.2.3 --- Coastal hydrography --- p.6 / Chapter 2.1.2.4 --- Biological factors --- p.6 / Chapter 2.1.3 --- Site description of the Zhujiang River estuary --- p.7 / Chapter 2.2 --- Introduction --- p.9 / Chapter 2.3 --- Materials and methods --- p.10 / Chapter 2.4 --- Results --- p.13 / Chapter 2.4.1 --- Physical parameters and chlorophyll concentration --- p.13 / Chapter 2.4.2 --- Seasonal and spatial variations in the abundance of planktonic copepods --- p.17 / Chapter 2.4.3 --- Seasonal variations in the relative abundance of dominant copepods --- p.27 / Chapter 2.4.4 --- Relationship between copepod abundance and chlorophyll a concentration --- p.26 / Chapter 2.4.5 --- Seasonal and spatial distribution and salinity and temperature preference of dominant copepods --- p.30 / Chapter 2.5 --- Discussion --- p.41 / Chapter 2.5.1 --- Seasonal variations in copepod abundance --- p.41 / Chapter 2.5.2 --- Seasonal and spatial variations in species diversity --- p.43 / Chapter 2.5.3 --- Seasonal and spatial distribution of dominant species --- p.45 / Chapter 2.5.4 --- Seasonal succession and spatial segregation of dominant copepods --- p.51 / Chapter 2.5.5 --- Seasonal and spatial distribution of non-dominant copepods --- p.52 / Chapter 2.6 --- Conclusion --- p.60 / Chapter Chapter 3. --- "Spatial and temporal distribution of marine cladocerans in Tolo Harbour, Hong Kong" --- p.61 / Chapter 3.1 --- Literature review --- p.61 / Chapter 3.1.1 --- Geographical and seasonal distribution of marine cladocerans --- p.61 / Chapter 3.1.2 --- Vertical distribution --- p.65 / Chapter 3.1.2.1 --- Diel vertical migration --- p.65 / Chapter 3.1.2.2 --- Marine cladocerans as epiplankters --- p.68 / Chapter 3.1.2.3 --- Diel vertical distribution of marine cladocerans --- p.69 / Chapter 3.1.3 --- Horizontal distribution --- p.70 / Chapter 3.1.4 --- Reproduction --- p.71 / Chapter 3.1.5 --- Feeding --- p.72 / Chapter 3.1.5.1 --- Food composition --- p.72 / Chapter 3.1.5.2 --- Diel feeding behaviour --- p.74 / Chapter 3.16 --- Site description of Tolo Harbour --- p.77 / Chapter 3.2 --- Introduction --- p.79 / Chapter 3.3 --- Materials and methods --- p.80 / Chapter 3.3.1 --- Field sampling --- p.80 / Chapter 3.3.1.1 --- Physical parameters --- p.80 / Chapter 3.3.1.2 --- Ambient chlorophyll concentration --- p.82 / Chapter 3.3.1.3 --- Zooplankton sampling --- p.82 / Chapter 3.3.1.4 --- Gut pigment content --- p.83 / Chapter 3.3.2 --- Measurement of gut evacuation rate --- p.84 / Chapter 3.3.2.1 --- Gut evacuation rate --- p.85 / Chapter 3.3.2.2 --- Clearance rate --- p.86 / Chapter 3.3.3 --- Zooplankton distribution --- p.86 / Chapter 3.3.3.1 --- Quantitative analysis --- p.86 / Chapter 3.3.4 --- Statistical analysis --- p.92 / Chapter 3.3.4.1 --- Overall population --- p.92 / Chapter 3.3.4.2 --- Size --- p.93 / Chapter 3.3.4.3 --- Reproductive condition --- p.94 / Chapter 3.3.4.4 --- Gut pigment content and gut clearance rate --- p.95 / Chapter 3.4 --- Results --- p.96 / Chapter 3.4.1 --- Physical parameters and chlorophyll concentration --- p.96 / Chapter 3.4.2 --- Spatial and temporal distribution of marine cladocerans --- p.102 / Chapter 3.4.2.1 --- Species composition and abundance --- p.102 / Chapter 3.4.2.2 --- Vertical and horizontal distribution in general population --- p.105 / Chapter 3.4.2.3 --- Vertical and horizontal patterns in size distribution --- p.110 / Chapter 3.4.2.4 --- Distribution of marine cladocerans at different stages --- p.118 / Chapter 3.4.3 --- Feeding ecology of marine cladocerans --- p.125 / Chapter 3.4.3.1 --- Did variation in gut pigment content --- p.125 / Chapter 3.4.3.2 --- Gut evacuation rate --- p.125 / Chapter 3.4.3.3 --- Diel changes in clearance rate of Penilia avirostris --- p.129 / Chapter 3.5 --- Discussion --- p.132 / Chapter 3.5.1 --- "Diel vertical and horizontal distribution of 3 marine podonids: Pseudevadne tergestina, Podon sp. and Pleopis schmackeri" --- p.135 / Chapter 3.5.2 --- Diel vertical and horizontal distribution of Penilia avirostris --- p.138 / Chapter 3.5.3 --- Size distribution of marine cladocerans --- p.140 / Chapter 3.5.4 --- Feeding behaviour of marine cladocerans --- p.142 / Chapter 3.6 --- Conclusion --- p.145 / References --- p.147

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 174-183.

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Various aspects of the feeding ecology of zooplankton are described for hypertrophic Hartbeespoort Dam, where the phytoplankton is dominated by the cyanophyte Microcystis. The study considers zooplankton succession, community grazing rates, and speciesspecific filtration rates on Microaystis colonies and natural bacterioplankton. Seasonal abundance of the main herbivorous zooplankton between 1981 and 1986 is described both in respect of biomass and specific densities. In situ community grazing rates were measured from January 1983 to March 1985 using 14C-Iabelled Chlorella . Zooplankton succession and community grazing rates are examined in relation to food quantity and quality. Experiments measuring species-specific filtration rates on labelled Chlorella and Microcystis colony fractions revealed low filtration rates for small-bodied cladoceran species on cyanophyte colonies. Daphnia fed significantly on Microcystis colonies up to 60-100 ).μm but Daphnia filtration rates on Chlorella were suppressed by ~707. during the mid-summer increase in Microcystis abundance. Filtration rates of small cladoceran species were not suppressed by MicpocystisJ which was not an important food resource . Cladoceran filtration rate:body length models were developed for Chlorella and Microcystis colony fractions as food. Multiple regression models explained variance in filtration rates on these foods as a function of body length, food type and size, grazer species and temperature (in order of significance). Inclusion of food quality factors such as cyanophyte colony size seems justified in models of plankton feeding in eutrophic or hypertrophic lakes. Methods for in situ measurement of zooplankton filtration rates on 'H-thymidine-Iabelled natural bacteria were improved for use under hypertrophic conditions, and associated isotope-adsorption errors were measured. Community, species-specific and length-specific filtration rates on bacterioplankton were measured (late-spring to late-summer 1986-87) . Ceriodaphnia exhibited no preference for bacteria or Chlorella. Other cladocerans preferred the algal food . Algal/bacterial selectivity coefficients of the zooplankton community revealed an increased algal preference following the mid-summer shift to phytoplankton dominance by largely inedible Microcystis. This implies that bacterioplankton is not an important food resource for the summer cladoceran community. Estimates of the contribution of bacterial carbon to the daily zooplankton carbon requirements are low. The implications of all results are discussed in relation to seasonal succession, the clear-water phase', and biomanipulation in this hypertrophic reservoir.

Although predation has been identified as a potentially important driver in terrestrial and freshwater ecosystems, estuarine planktonic research has focused largely on the so-called "bottom-up" drivers of community assemblages. As such, this thesis focuses on the direct and indirect effects of zooplanktivorous predators on the planktonic community in an estuarine environment. By using a suite of in situ mesocosm experiments, a number of hypotheses, pertaining to the major research themes associated with predator-prey interactions, are tested. These themes included trophic cascading, risk effects associated with predation events and the importance of predator diversity in maintaining prey communities. The first experiment assessed the significance of apex predation pressure for the planktonic community through trophic cascades. Various treatments using in situ mesocosms were established in a closed oligotrophic estuary to highlight the importance of predation in stabilising estuarine plankton abundances. Through either the removal (filtration) or addition of certain planktonic groups, varied trophic scenarios were established. The experimental treatment containing apex zooplanktivores had consequences for multiple trophic levels, exerting a stabilising pressure throughout the food web (Chapter 3). Furthermore, pyrosequencing of filtered water samples revealed that when compared to the remaining treatments, the treatment containing stable apex predatory pressure experienced limited temporal deviation-from-initial in bacterial community structure (Chapter 4). These findings are consistent with trophic cascade theory whereby predators mediate interactions at multiple lower trophic levels with consequent repercussions for diversity. To assess the non-consumptive effects of predators on prey, two experiments were conducted. Firstly, using egg numbers per clutch as a measure of potential reproductive output, the non-lethal effects of predatory pressure on reproductive success in a key planktonic copepod was investigated. In this study, the average clutch size of fecund female copepods was found to be consistently lower in the presence of predators when compared to females not exposed to predation threat (Chapter 5). The second study assessed the effects of conspecific chemical alarm cues associated with predation, on population dynamics of a copepod species. This study revealed that the copepods appear to detect the presence of chemical alarm cues associated with predation events, with repercussions for population demographics over time. Furthermore, it showed that in the absence of actual predation, copepod prey responses to alarm cues were adjusted over time, consistent with the threat sensitive predator avoidance hypothesis (Chapter 6). The final data chapter dealt with predator diversity and its implications for zooplankton community structure. By experimentally monitoring the effects of two alternate model predators on the metazoan community over time, dissimilarities in community level control emerged. Alternate key prey populations were regulated by the different model predators, highlighting the importance of predator and prey behaviour in mediating predator-prey interactions (Chapter 7). These results highlight the potential importance of predators in maintaining community dynamics in estuarine planktonic communities under certain conditions. This study represents some of the first work to address these various aspects of predator-prey dynamics within the context of planktonic estuarine ecology.

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