Thesis (Ph. D.)--University of Wisconsin--Madison, 1973. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The overall aim of this thesis was to determine the relative importance of heterotrophy and autotrophy in lake plankton. Empirical analyses using extensive surveys of literature data revealed three specific patterns in metabolism and biomass structure in freshwater plankton. First, the ratio of phytoplankton production to plankton respiration (P/R ratio) tends to be low in unproductive lakes ($<$1), and increases along gradients of enrichment. Second, the contribution of planktonic heterotrophs (bacteria and zooplankton) to community respiration is highest in oligotrophic lakes. Third, planktonic heterotrophs dominate community biomass in oligotrophic lakes, whereas phytoplankton increasingly dominate plankton biomass along gradients of enrichment. These three distinct patterns were then tested simultaneously in a set of lakes that span a wide trophic gradient. Results indicated that the plankton of oligotrophic and mesotrophic lakes were characterized by P/R ratios well below unity, and a high contribution of heterotrophs to both community respiration and biomass. These trends are completely the opposite in the most productive lakes. The plankton communities of oligotrophic temperate lakes are predominantly heterotrophic and extensively utilize external inputs of carbon, and therefore only the plankton of eutrophic lakes conformed to the classical phytoplankton-based food web. In most lakes, excess heterotrophic activity could be supported by inputs of organic matter from the drainage basin. Excess plankton respiration, fueled by allochthonous organic carbon, could represent an important source of CO$ sb2$ to lakes.

No description available.

No description available.

This study investigated the relationship between flood duration of beaver ponds in eastern Ontario and their productivity for waterfowl. The primary objective was to assess the effect of removing water from a beaver pond for one year had on the subsequent productivity of the wetland. Productivity was estimated by sampling water chemistry, standing crops of aquatic invertebrates, vertebrates, algae and vegetation composition and distribution in naturally occurring and managed beaver ponds of varying ages during 1994 and 1995. Three ponds in each of the following categories were sampled; managed ponds reflooded in 1993, managed ponds reflooded in 1991, naturally occurring beaver ponds reflooded in 1992-93, and naturally occurring old flood ponds ($>$5 years old). / Results from this study indicate that beaver pond productivity is negatively affected by flooding duration. Removal of a portion of the beaver dam on old flood ponds may be an effective means of rejuvenating the wetland. Positive effects on the productivity of the wetland should be realized for several years after reflood. Variability in results indicates that other environmental variables were also affecting the overall productivity of beaver ponds. (Abstract shortened by UMI.)

No description available.

No description available.

Differences in primary production and periphyton and macroinvertebrate biomass between pairs of constrained (valley floor width of less than twice the active channel width) and unconstrained reaches were investigated in Elk River and four tributaries in southwest Oregon. In August 1991, macroinvertebrates were sampled from individual cobbles, and rocks were collected to determine periphyton biomass. In August 1992, gross primary production was estimated in the four tributaries using closed, non-circulating chambers. Unconstrained reaches received approximately twice as much direct solar radiation (measured with a Solar Pathfinder) as constrained reaches. Gross primary production in unconstrained reaches was double that of constrained reaches. Periphyton biomass did not differ between reach types. Total macroinvertebrate biomass was 38% greater in unconstrained reaches, where scraper biomass was 2.4 times that of constrained reaches. When regressed across streams, gross primary production, macroinvertebrate biomass, and scraper biomass were positively associated with solar radiation. Greater solar radiation in unconstrained reaches is the most apparent causal mechanism for greater gross primary production, which in turn may cause greater macroinvertebrate biomass in unconstrained reaches. Greater invertebrate consumption in unconstrained reaches may limit periphyton accrual, keeping standing crops at levels similar to those found in constrained reaches. When identifying variables that shape biotic communities and determine productive potential, channel constraint is important. / Graduation date: 1994

Mémoire (M.Sc. pures) --Université du Québec à Chicoutimi, 1986. / Document électronique également accessible en format PDF. CaQCU

M.Sc. (Botany) / Eight sampling points were selected on the Jukskei River so that the impact of inflows from various localities on the quality of the river water could be determined. Samples were taken every two weeks from the 4th April 1983 to 19th March 1984. The temperature, conductivity, dissolved oxygen and pH of the water were determined on site. Determinations of total phosphorus (as p-po1-), nitrate (NO), chloride (C11 and chlorophyll a were done. After filtration the water of each sample was inoculated with Euglena gracilis and incubated for four days under controlled conditions after which the Euglena chlorophyll-content, primary productivity and biological growth potential were measured...