Daphnia versus copepod impact on summer phytoplankton: functional compensation at both trophic levels.

Sommer, Ulrich, Sommer, Frank, Santer, B., Zöllner, E., Jürgens, K., Jamieson, C., Boersma, M. and Gocke, Klaus (2003) Daphnia versus copepod impact on summer phytoplankton: functional compensation at both trophic levels. Oecologia (135). pp. 639-647. DOI 10.1007/s00442-003-1214-7.

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Abstract

Here we report on a mesocom study performed to compare the top-down impact of microphagous and macrophagous zooplankton on phytoplankton. We exposed a species-rich, summer phytoplankton assemblage from the mesotrophic Lake Schöhsee (Germany) to logarithmically scaled abundance gradients of the microphagous cladoceran Daphnia hyalina×galeata and of a macrophagous copepod assemblage. Total phytoplankton biomass, chlorophyll a and primary production showed only a weak or even insignificant response to zooplankton density in both gradients. In contrast to the weak responses of bulk parameters, both zooplankton groups exerted a strong and contrasting influence on the phytoplankton species composition. The copepods suppressed large phytoplankton, while nanoplanktonic algae increased with increasing copepod density. Daphnia suppressed small algae, while larger species compensated in terms of biomass for the losses. Autotrophic picoplankton declined with zooplankton density in both gradients. Gelatinous, colonial algae were fostered by both zooplankton functional groups, while medium-sized (ca. 3,000 µm3), non-gelatinous algae were suppressed by both. The impact of a functionally mixed zooplankton assemblage became evident when Daphnia began to invade and grow in copepod mesocosms after ca. 10 days. Contrary to the impact of a single functional group, the combined impact of both zooplankton groups led to a substantial decline in total phytoplankton biomass.

Document Type: Article
Keywords: Phytopankton, Zooplankton, Copepoda, Cladocera, Top-down-control
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-N Experimental Ecology - Food Webs
OceanRep > GEOMAR > FB3 Marine Ecology
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00442-003-1214-7
ISSN: 0029-8549
Date Deposited: 18 Feb 2008 17:26
Last Modified: 23 Sep 2019 19:48
URI: http://oceanrep.geomar.de/id/eprint/2515

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