Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Akademische Abhandlung--Lund. / Extra t.p. with thesis statement, inserted. "Berichtigungen": leaf inserted. Summary in English. Bibliography: p. [281]-288.

Studies have been carried out on the phytoplankton of two freshwater lakes-eutrophic Rostherne Mere (Cheshire, UK) and mesotrophic Lake Glubokoe (Moscow region, Russia). Diversity was investigated in relation to two major aspects : (a) species composition, with indices of diversity being estimated from phytoplankton cell and colony counts, and (b) intraspecific diversity, looking at variation in elemental composition within selected species. The major genera of phytoplankton in Rostherne Mere included Stephanodiscus and Asterionella (spring diatom bloom), Chlamydomonas and Sphaerocystis (clear water phase), and a species assembly dominated by Microcystis (1997) or Ceratium (1999) in the late summer/autumn bloom. The sequence of major algal groups recorded at Lake Glubokoe were: chrysophytes, dinoflagellates and diatoms in spring, chlorophytes and blue-greens in the clear water phase, and an assembly of diatoms, blue-greens, dinoflagellates and chrysophytes in the late summer/autumn bloom. Indices of species diversity were determined in relation to species richness (Richness index, species count), general diversity (Shannon index) and species dominance (Simpson index). In both lakes, species richness and general diversity were greatest in the late summer bloom, a period of maximum phytoplankton stability and high productivity, characterised by K-selected species. Species dominance in Rostherne Mere was highest at extremes of productivity, including times of low algal biomass (clear water phase, 1997 and 1999) and very high biomass (late summer bloom, 1999). In Lake Glubokoe species dominance was maximal at the end of the summer/autumn bloom, a period of intermediate productivity and dominance of a limited number of species. Overall diversity (maximum seasonal Shannon index) decreased with increase in productivity, being highest in Lake Glubokoe (1998, low productivity), intermediate in Rostherne Mere 1997, and lowest in Rostherne Mere 1999 (highest chlorophyll-a levels). Phytoplankton diversity within the water column (mid-day) was determined at the key phases in lake stratification in Rostherne Mere (1999) and at the period of late summer bloom in Lake Glubokoe (1998). At each phase of the seasonal growth cycle, differences in the vertical distribution of individual species and algal groups reflected positioning of algae in relation to ambient conditions (nutrients, light, temperature, density gradients) or sedimentation within the water column. Phytoplankton diversity in species richness closely corresponded to the overall phytoplankton population (biomass profile and individual counts), usually having the maximum values in the epilimnion. Profiles of species dominance varied markedly in some of the depth analyses. High species dominance reflected either the growth of individual species (surface populations of chlorophytes in the clear water phase -Rostherne Mere) or the accumulation of populations at a particular depth due to sedimentation (hypolirrmion peak of diatoms in Lake Glubokoe). Phytoplankton statistical groups and assemblages were analysed within the water column of Rostherne Mere at the time of markedly high algal productivity (late summer bloom in 1999). Intraspecific diversity was examined on the basis of elemental composition of three main species (Ceratium hirundinella, Anabaena flos-aquae and Microcystis aeruginosa), sampled within the same water column in Rostherne Mere. The elemental composition of single cells within a mixed phytoplankton preparation was determined using Electron Probe X-ray Microanalysis. Intraspecific variation was investigated in relation to differences in elemental composition within the water column, variation within micropopulations, and pattern of elemental correlation. X-ray analysis detected a similar range of elements in the populations of Ceratium, Anabaena and Microcystis: magnesium, silicon, phosphorus, sulphur, chlorine, potassium, calcium, with P as the major anionic element, K as the major cation. Si was present at substantial levels. Elemental composition varied considerably within micropopulations of each species. Variation in the concentration of most elements was unimodal. Bimodal distribution was shown by K in Ceratium cells, and by Si in Anabaena and Microcystis cells, indicating particular subpopulations, within these species. Distinct subpopulations of high-Si and low-Si cells in Anabaena and Microcystis were attributed to the presence of Si as a surface layer associated with Al in high-Si cells. Low-K cells in Ceratium were seen as part of the population undergoing senescence. The pattern of elemental correlations revealed a major statistical association between Mg, P, S and K in each species throughout the water column. The XRMA results suggested an underlying homogeneity in the elemental composition of Ceratium, Anabaena and Microcystis within the top 8 m of the water column.

Biomass of phytoplankton in large rivers may be maintained or even increased by inputs from hydraulic "dead zones". In some eutrophic rivers, dead zones can increase water retention time sufficiently for the development of algal concentrations substantially higher than in the main channel. "Seeding" of the main channel may then occur through the interchange of water between dead zones and the main channel. The objective of this thesis was to investigate the role of dead zones in the development of phytoplankton along the moderately eutrophic Rideau River. In the first chapter, I compare the suspended algal communities in dead zones and the adjacent main channel of the Rideau, to evaluate the assumption that dead zones support higher phytoplankton biomass. In the second chapter, I test the assumption that dead zones contribute algal biomass to the main channel of rivers. To do this, I examine the relationship between changes in main channel total chlorophyll a and the proportion of dead zone (inferred from the area of shallow macrophyte-dominated water) in 40 reaches along the Rideau, averaging approximately 2 km each. (Abstract shortened by UMI.)

Five different substrates (sand, fine gravel, coarse gravel, cobble and boulder) in nine streams forming a trophic gradient in the Ottawa Valley have been sampled in June 1992 to determine the effect of trophic level and substrate size on benthic communities. Total biomass of invertebrates (B, mg dry mass m$\sp{-2})$ and periphyton are strongly related to substrate particle size $(\Phi$, $-$Log$\sb2$diameter in mm) and trophy, represented by total phosphorus concentration (P, $\mu$g L$\sp{-1}).$ The model for periphyton biomass (Log$\sb $Peri = $-$0.08 $-$ 1.68Log$\sb $P + 1.08Log$\sb $P$\sp2\ -$0.13$\Phi\sp2)$ explains 67% of the observed variability and the model for invertebrate biomass (Log$\sb $B = 2.69 + 0.55Log$\sb $P + 0.3Log$\sb $Peri $-\ 0.01\Phi\sp2\ -$ 0.02Z) explains 68% of the observed variability (Peri = periphyton biomass in mgChla m$\sp{-2}$ and Z = depth in cm). The highest invertebrate biomass is observed on intermediate-size substrate (gravel) in phosphorus-rich streams. Periphyton biomass peaks on coarse substrates (boulder and cobbles) in streams where total phosphorus concentration is high $(>$50$\mu$gL$\sp{-1}).$ Individual body mass (W$\sb{\rm moy})$ is not affected by substrate size but is positively correlated with total phosphorus concentration (Log$\sb $W$\sb{\rm moy}$ = 1.67 $-$ 1.71Log$\sb $P + 0.96Log$\sb $P$\sp2,$ R$\sp2$ = 0.44). The effect of phosphorus and substrate on total biomass and mean individual body mass, are reflected in the size distribution of the invertebrates. Although the shape of the distribution is constant (unimodal), abundance of medium and large organisms increases in phosphorus-rich streams on intermediate-size substrates. A polynomial model including phosphorus concentration and substrate particle size is presented to quantify those variations of the size spectra. The predictions of this model are close to the observed values (R$\sp2$ = 0.89, residual mean square = 0.075) and this model could be very useful for a fast estimation of invertebrate size spectra.

No description available.

Two studies on the effects of enhanced ultraviolet-B radiation (UVB; 280--320 nm) on planktonic organisms of Canadian High Arctic lakes are presented. In the first study, the long-term effects of a moderate increase in UVB levels on the planktonic community of a lake were evaluated using in situ mesocoms. Four mesocosms (3 m square and 3 m deep) were placed in Two Basin Lake, a small lake (14.2 ha) located on Ellesmere Island (79°55.5'N, 84°40'W; Nunavut, Canada). For 27 days, two mesocosms were exposed to full sunlight (including ambient UVB) while two others were exposed to sunlight plus artificially enhanced UVB. Chlorophyll a, zooplankton mean length and carbon allocation into macromolecular constituents were not affected by enhanced UVB. Phytoplankton productivity displayed diverse and inconsistent responses to enhanced UVB. Picocyanobacteria abundance decreased in the enhanced UVB mesocosms, but only at the surface. Enhanced UVB generally increased heterotrophic bacterial abundance and activity. Heterotrophic nanoflagellates and zooplankton abundances increased in the enhanced UVB treatment after 14 days. The cladocerans and rotifers were positively affected by UVB, while the copepods were negatively affected. The high levels (≥ 5 mg L -1) of dissolved organic carbon (DOC) in this lake combined with vertical mixing generally protected the planktonic community from direct damage by enhanced UVB. It is hypothesized that UVB may have indirectly stimulated the microbial food web and the rest of the food chain through increased photodegradation of high molecular weight refractory dissolved organic matter into more bioavailable nutrients. In the second study, the short-term (2 to 24 h) effects of enhanced UVB on carbon uptake rates, photosynthetic fractionation into three size classes (picoplankton [0.2-2 mum], nanoplankton [2-20 [mum] and netplankton [> 20 mum]) and carbon assimilation into the four main end-products (low molecular weight metabolites [LMW], lipid, polysaccharide and protein) were assessed for nine lakes located near Resolute (74°15'N, 94°50'W) on Cornwallis Island (Nunavut, Canada). These lakes have low DOC levels (≤ 2 mg L-1). For each lake, 14C-inoculated water samples were exposed to 6, 25, 50 and/or 100% surface irradiance levels (E o) under natural solar radiation (including ambient UVB) or solar radiation plus artificially enhanced UVB. (Abstract shortened by UMI.)

No description available.

No description available.