Thesis (Ph. D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [75]-79).

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No description available.

Body size influences virtually all aspects of the autecology of material flow by organisms. Thus, size classes may be considered as alternatives to grouping by trophic level, function or taxonomy to describe the structure and function of communities. The general intent of this thesis is to assess the role of body size in the dynamics of radiophosphorus in the freshwater plankton. To calculate a priori estimates of the fluxes of phosphorus through size classes of plankton, the rates of assimilation and excretion of laboratory cultures of algae and cladocerans were measured, and regressed on body mass (W). In both groups, assimilation increased as W('0.75). The turnover of body phosphorus was described as a two-compartment system. The turnover rates of the small (2-5% of body P) fast turnover pool, the large (95-98%) slow turnover pool, and that of the body phosphorus fell proportionately to W('- 1/4) in algae and W('- 1/2) in zooplankton. Field tests of allometric models of radiophosphorus flow were conducted by following the redistribution of radioactivity among 11 size fractions of enclosed epilimnetic assemblages over 5 to 6 days. Concentration of the tracer in the biomass declined with size soon after addition and gradually shifted to a uniform distribution within 3 days. A model that makes no a priori assumptions as to the trophic structure of the system, i.e. all size classes are at the same trophic level, predicted these dynamics better than one that assumes trophic position to increase with size. Further analyses indicated that explicit treatment of the physiological allometry and size distribution of broad functional groups of plankton are needed to improve the descriptive power of the model further.

The hypothesis that aquatic biomass is uniformly distributed over logarithmic size classes was evaluated with samples from epilimnetic plankton communities. Although the hypothesis is true for oligotrophic lakes, biomass increases between successive size classes in mesotrophic and eutrophic lakes. The abundance of organisms in logarithmic size intervals is strongly negatively correlated with size. The relationship between organism size and physiological performance in mixed communities was examined by testing the hypothesis that limnoplankton respiration rates are predictable functions of mean body size. The equation governing this relationship was found to be similar to those obtained with laboratory cultures. The total epilimnetic phosphorus concentration is correlated with both biovolume and respiration rate. Many limnological relationships, including those established in this thesis, are based on linear regressions between log-transformed variables. The rules for the correct use of backtransformed predictions are elucidated. A theorem is proven, which sets limits to the relationship between the coefficients of determination on the original and transformed scales. Simulated data and empirical results are used to illustrate the applications and limitations of the theoretical results.

Thesis (doctoral)--Ludwig-Maximilians-Universität München, 2006. / Title from PDF t.p. (viewed on May 14, 2006). Includes reprints of papers co-authored with others. Vita. Includes bibliographical references.

Thesis (Ph.D.)--Kent State University, 2006. / Title from PDF t.p. (viewed Mar. 5, 2009). Advisor: Robert T Heath. Keywords: bacterioplankton, phosphorus dynamics, bacterial bioenergetics, labile dissolved organic carbon, bacterial productivity, bacterial respiration, bacterial growth efficiency, Lake Erie, hypoxia. Includes bibliographical references (p. 357-397).

M.Sc. (Zoology) / Please refer to full text to view abstract

The purpose of this investigation is to attempt to relate the distribution and periodicity of the plankton to the variations in the biological, chemical, and physical factors.

Several lakes located in the blast zone of the 1980 eruption of Mount St. Helens were studied to determine if the plankton in the lakes were limited in their growth by nitrogen or phosphorus availability. Long term nutrient enrichment experiments were performed on lake water from five lakes and measures of chlorophyll-a, carbon fixation, and nutrient uptake were used to evaluate the extent of limitation. Nutrient concentrations, ratios, and uptake from 14 lakes provided additional evidence for limitation by nitrogen and/or phosphorus. The physical, chemical, and biological characteristics of the lakes were also examined to monitor the return of these lakes to pre-eruption conditions. Lakes heavily impacted by the 1980 eruption (Ryan, Fawn, and Hanaford Lakes) and newly formed Castle Lake produced positive responses to nitrogen additions, reflecting the continuing importance of nitrogen in these lakes. Evidence for colimitation by phosphorous was apparent in some of the lakes. Venus Lake, located near the fringe of the blast zone received less organic debris and responded only with phosphorus additions. Evaluations of nutrient depletion from the photic zones of these lakes during the growing season supported the results from the bioassays. Two measures of growth (chlorophyll-a and carbon fixation) often responded differently to enrichment, suggesting active algal and bacterial communities in some of the lakes. Qualitative measures of alkaline phosphatase activity normalized to chlorophyll-a indicated that those lakes which contained the highest dissolved organic carbon and bacterial counts following the eruption had higher alkaline phosphatase activities than less impacted lakes, suggesting bacterial enzyme production. Alkaline phosphatase activity confirmed that phosphorus limitation was more severe in lakes having less soluble reactive phosphorus. Most of the lakes appear to be similar to other Cascade Mountain lakes, although many have reduced dissolved oxygen concentrations in the bottom waters during stratification. Incomplete mixing of these lakes during periods of circulation may regulate the decomposition of the organic material and hence, full recovery of these lakes.