Inter-Research
Aquatic Microbial Ecology

ABSTRACT: Although a range of over 30o/oo in stable carbon isotope ratios has been recorded for freshwater plankton, no extensive synoptic survey has been undertaken to examine whether any environmental or ecophysiological determinants of delta¹³C exist. Here we reanalyze existing literature data on the seasonal variation in plankton delta¹³C from eutrophic lakes, and collect new data on mid-summer zooplankton delta¹³C from 52 Canadian Shield lakes, to demonstrate that plankton become enriched in ¹³C relative to ¹²C under conditions of high productivity and low pCO₂. Low zooplankton delta¹³C signatures in humic/dystrophic lakes of high DOC (dissolved organic carbon) concentration and colour, and in clearwater lakes with high rates of epilimnetic respiration and hypolimnetic metabolism, suggest that the ¹³C-depletion observed in oligotrophic lakes is probably due to heterotrophic activity.

KEY WORDS: Zooplankton delta¹³C · Lake productivity · Heterotrophy

Published in AME Vol. 12, No. 1 (1997) on January 30
Print ISSN: 0948-3055; Online ISSN: 1616-1564. Copyright © Inter-Research, Oldendorf/Luhe, 1997