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Long‐term Annual and Seasonal Changes of Meta‐ and Protozooplankton in Lake Müggelsee (Berlin): Effects of Eutrophication, Grazing Activities, and the Impact of Predation
Author(s) -
Arndt Hartmut,
Krocker Maria,
Nixdorf Brigitte,
Köhler Antje
Publication year - 1993
Publication title -
internationale revue der gesamten hydrobiologie und hydrographie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 0020-9309
DOI - 10.1002/iroh.19930780308
Subject(s) - zooplankton , biology , predation , grazing pressure , phytoplankton , eutrophication , ecology , grazing , crustacean , nutrient
Annual changes of rotifers, copepods, cladocerans, the ciliate Epistylis rotans , and larvae of Dreissena polymorpha were analysed for the period 1908–1990. Though food resources increased 6–10 fold in the course of eutrophication, only rotifers and Epistylis increased accordingly. Probably as a result of increased predation pressure crustaceans increased only twice. The seasonal pattern of metazoans and protozoans (flagellates, sarcodines, ciliates) were analysed for 12 and 3 years, resp. During winter and spring, large heterotrophic flagellates and ciliates dominated the zooplankton and were responsible for a pronounced ‐ formerly underestimated ‐ grazing pressure on phytoplankton. In early summer, metazoan filter‐feeders were often able to cause a significant reduction of phyto‐ and protozooplankton. However, during some years, phytoplankton declined in the absence of a pronounced grazing pressure. Field data and experiments revealed that predators were able to regulate the density of cladocerans in early summer (mainly cyclopoids) and summer (mainly Leptodora , smelt and fish juveniles).