Oecologia

, Volume 135, Issue 4, pp 639–647

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

  • Ulrich Sommer
  • Frank Sommer
  • Barbara Santer
  • Eckart Zöllner
  • Klaus Jürgens
  • Colleen Jamieson
  • Maarten Boersma
  • Klaus Gocke
Community Ecology

DOI: 10.1007/s00442-003-1214-7

Cite this article as:
Sommer, U., Sommer, F., Santer, B. et al. Oecologia (2003) 135: 639. doi:10.1007/s00442-003-1214-7

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.

Keywords

Phytopankton Zooplankton Copepoda Cladocera Top-down-control 

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Ulrich Sommer
    • 1
  • Frank Sommer
    • 1
  • Barbara Santer
    • 2
  • Eckart Zöllner
    • 2
  • Klaus Jürgens
    • 2
  • Colleen Jamieson
    • 2
  • Maarten Boersma
    • 3
  • Klaus Gocke
    • 1
  1. 1.Institut für MeereskundeKielGermany
  2. 2.Max-Planck-Institut für LimnologiePlönGermany
  3. 3.Alfred-Wegener-InstitutBAHHelgolandGermany

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