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Phytoplankton succession in microcosm experiments under simultaneous grazing pressure and resource limitation
Author(s) -
Sommer Ulrich
Publication year - 1988
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1988.33.5.1037
Subject(s) - phytoplankton , zooplankton , grazing pressure , microcosm , nutrient , algae , daphnia , grazing , biology , eutrophication , ecology , plankton , competition (biology) , dominance (genetics) , environmental science , biochemistry , gene
The influence of grazing pressure on the occurrence and outcome of nutrient competition among planktonic algae was studied in two‐chamber microcosms where there was a flow in both directions between a light reactor without zooplankton and a dark reactor with zooplankton ( Daphnia longispina and Daphnia magna ). The phytoplankton inoculum was a mixed, natural assemblage. Zooplankton could influence the dynamics of phytoplankton both by selective grazing and by differential excretion of limiting nutrients. Grazing pressure did not prevent the occurrence of nutrient limitation in algae and, hence, of nutrient competition between them. Zooplankton did, however, influence the outcome of competition by lowering Si: P ratios. A comparison with my previous experiments shows that diatoms need higher Si: P supply ratios for dominance over green algae in the presence of grazers than in grazing‐free competition with steady or weekly pulsed nutrient supply.