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Heterotrophic Uptake and Transformation of Phytoplankton Extracellular Products

Heterotrophic Uptake and Transformation of Phytoplankton Extracellular Products Abstract Phytoplankton produce extracellular material at a relatively constant rate (8-9% of total primary production) when incubated for a period of <6 hr. The relative amount of exudates composed of large molecular weight material increased with longer incubation times, presumably because of a lag time before the label was introduced into these more complicated molecules. Additional incubation of the excreted material in the dark after the phytoplankton had been removed resulted in a still larger relative amount of labelled exudates of higher molecular weight. This could result from microheterotrophs altering the phytoplankton exudates into material with larger molecular weight, or a greater refractoriness of the original large molecular weight material. Both processes probably occurred. Compounds smaller than 500 MW are mainly respired by microheterotrophs. Compounds higher than 500 MW are taken up at slower rates. About 25--30% of the labe! released by the phytoplankton remained in the extracellular metabolite pool after 3 days. Introduction Phytoplankton under natural conditions release extracellular metabolites (Fogg et al. 1965, Anderson and Zeutschell 1970, Storch and Saunders 1975, 1978, Mague et al. 1980). These metabolites or exudates are composed of small simple organic compounds (Hellebust 1965, Fogg 1966, Saunders 1972, Storch arid Saunders http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Botanica Marina de Gruyter

Heterotrophic Uptake and Transformation of Phytoplankton Extracellular Products

Iturriaga, R.; Zsolnay, A.
Botanica Marina , Volume 26 (8) – Jan 1, 1983
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Publisher
de Gruyter
Copyright
Copyright © 2009 Walter de Gruyter
ISSN
0006-8055
eISSN
1437-4323
DOI
10.1515/botm.1983.26.8.375
Publisher site
See Article on Publisher Site

Abstract

Abstract Phytoplankton produce extracellular material at a relatively constant rate (8-9% of total primary production) when incubated for a period of <6 hr. The relative amount of exudates composed of large molecular weight material increased with longer incubation times, presumably because of a lag time before the label was introduced into these more complicated molecules. Additional incubation of the excreted material in the dark after the phytoplankton had been removed resulted in a still larger relative amount of labelled exudates of higher molecular weight. This could result from microheterotrophs altering the phytoplankton exudates into material with larger molecular weight, or a greater refractoriness of the original large molecular weight material. Both processes probably occurred. Compounds smaller than 500 MW are mainly respired by microheterotrophs. Compounds higher than 500 MW are taken up at slower rates. About 25--30% of the labe! released by the phytoplankton remained in the extracellular metabolite pool after 3 days. Introduction Phytoplankton under natural conditions release extracellular metabolites (Fogg et al. 1965, Anderson and Zeutschell 1970, Storch and Saunders 1975, 1978, Mague et al. 1980). These metabolites or exudates are composed of small simple organic compounds (Hellebust 1965, Fogg 1966, Saunders 1972, Storch arid Saunders

Journal

Botanica Marina – de Gruyter

Published: Jan 1, 1983

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