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The influence of humic substances on lacustrine planktonic food chains

The influence of humic substances on lacustrine planktonic food chains Abstract Humic substances (HS) might influence planktonic food chains in lakes in two ways: 1) by altering the physical or chemical environment and thus modifying autotrophic primary production and the dependent food chains; 2) by acting as a direct carbon/energy source for food chains. HS compete with phytoplankton for available quanta underwater and this effect is seen in the reduced euphotic zone depth in lakes with high concentrations of HS. Thus potential photosynthetic production is lower in the presence of HS. However, this effect can be offset in small lakes in which the depth of mixing is also reduced when HS concentrations are high. Complexation by HS of important nutrients such as iron and phosphorus may also restrict primary production. Evidence is accumulating that photosynthetic primary production is insufficient to support measured metabolic activity in humic lakes, which implies that metabolism of allochthonous HS underpins much of the observed activity. Studies of bacterial abundance and growth in the presence of HS support the view that bacteria are the most significant utilisers of HS. This use is apparently facilitated by photolysis of HS, particularly by short wavelength radiation. Bacteria are grazed by both micro-zooplankton (heterotrophic and mixotrophic flagellates and ciliates) and macrozooplankton. It is within this microbial community that the food chains derived from autotrophic and allotrophic sources interact. These effects of HS on food chains are discussed in relation to possible implications for the response of different lake types to eutrophication. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Hydrobiologia Springer Journals

The influence of humic substances on lacustrine planktonic food chains

Jones, Roger I.
Hydrobiologia , Volume 229 (1): 19 – Feb 1, 1992
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References (148)

Publisher
Springer Journals
Copyright
1992 Kluwer Academic Publishers
ISSN
0018-8158
eISSN
1573-5117
DOI
10.1007/BF00006992
Publisher site
See Article on Publisher Site

Abstract

Abstract Humic substances (HS) might influence planktonic food chains in lakes in two ways: 1) by altering the physical or chemical environment and thus modifying autotrophic primary production and the dependent food chains; 2) by acting as a direct carbon/energy source for food chains. HS compete with phytoplankton for available quanta underwater and this effect is seen in the reduced euphotic zone depth in lakes with high concentrations of HS. Thus potential photosynthetic production is lower in the presence of HS. However, this effect can be offset in small lakes in which the depth of mixing is also reduced when HS concentrations are high. Complexation by HS of important nutrients such as iron and phosphorus may also restrict primary production. Evidence is accumulating that photosynthetic primary production is insufficient to support measured metabolic activity in humic lakes, which implies that metabolism of allochthonous HS underpins much of the observed activity. Studies of bacterial abundance and growth in the presence of HS support the view that bacteria are the most significant utilisers of HS. This use is apparently facilitated by photolysis of HS, particularly by short wavelength radiation. Bacteria are grazed by both micro-zooplankton (heterotrophic and mixotrophic flagellates and ciliates) and macrozooplankton. It is within this microbial community that the food chains derived from autotrophic and allotrophic sources interact. These effects of HS on food chains are discussed in relation to possible implications for the response of different lake types to eutrophication.

Journal

Hydrobiologia – Springer Journals

Published: Feb 1, 1992

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