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Heterotrophy in lake plankton

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.

Identiferoai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41362
Date January 1993
CreatorsDel Giorgio, Paul A.
ContributorsPeters, R. H. (advisor)
PublisherMcGill University
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
LanguageEnglish
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Formatapplication/pdf
CoverageDoctor of Philosophy (Department of Biology.)
RightsAll items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated.
Relationalephsysno: 001396223, proquestno: NN94608, Theses scanned by UMI/ProQuest.

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