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AME 34:247-261 (2004)
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Abstract
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Ciliate dynamics in response to changing biotic and abiotic conditions in a large, deep lake (Lake Constance)
Ursula Gaedke1,*, Stephen A. Wickham2,3
1Institut für Biochemie und Biologie, University of Potsdam, Maulbeerallee 2, 14415 Potsdam, Germany
2University of Cologne, Zoological Institute, Weyertal 119, 50923 Cologne, Germany
3Present address: Zoological Institute, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria
*Email: gaedke@rz.uni-potsdam.de
ABSTRACT: From 1987 to 1998, ciliates and their prey and predator communities in Lake Constance (which is large, deep and meso-eutrophic) were intensively studied as the lake underwent re-oligotrophication. Ciliate biomass exhibited the bimodal seasonal
distribution typical for meso-eutrophic lakes, with high biomass in spring and summer and low biomass in winter and during the clear-water phase. Cluster analysis produced 9 groups of temporally co-occurring ciliate morphotypes with potentially similar
ecological characteristics. The clusters exhibited a larger seasonality than found in the size distribution, showing that size alone failed to capture some ciliate seasonal dynamics. Ciliate biomass declined by approx. 30% during the 12 yr of study, i.e.
considerably less than daphnids (and total phosphorus). This yielded a significant increase in the ratio between summer ciliate and daphnid biomass as re-oligotrophication progressed, in contrast to previous studies. Few indications for a mechanistic link
between phosphorus concentrations (which declined 3-fold during the study period) and ciliate biomass or community composition via group-specific food concentrations were found. The relative contribution of 3 of the 9 clusters changed as
re-oligotrophication progressed. Ciliate size distribution was related to re-oligotrophication and daphnid biomass in summer. The smallest and largest ciliates gained importance when daphnids decreased, whereas the biomass of large ciliates declined.
Generally, summer daphnid biomass had a greater predictive power for attributes of the ciliate community than the other factors studied (phosphorus, prey biomass, copepod biomass). The extent of bottom-up and top-down control of ciliates appeared to be
time- and group-specific. Overall, the ciliate community exhibited remarkably recurrent seasonal patterns, despite major alternations in abiotic and biotic conditions.
KEY WORDS: Ciliates · Long-term observations · Bottom-up control · Top-down control · Eutrophication · Daphnids · Copepods
Full text in pdf format
Published in AME Vol.
34, No. 3
(2004) on March 9
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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