QUEIMALIÑOS claudia Patricia
Impact of different zooplankton structures on the microbial food web of a South Andean oligotrophic lake
MODENUTTI, BE; QUEIMALIÑOS, CP; BALSEIRO, EG; REISSIG, M
ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY
Lugar: París; Año: 2003 vol. 24 p. 289 - 298
In oligotrophic Andean lakes, omnivorous calanoid copepods are the dominant zooplankters and, remarkably, phototrophic nanoflagellates and mixotrophic ciliates are the prevailing primary producers. In Lake Rivadavia Patagonia, Argentina), the centropagids Boeckella michaelseni and Parabroteas sarsi coexist with the large cladoceran Daphnia middendorffıana. The particular feeding modes of these zooplanktonic species probably impact differentially on the microbial community. To determine the effect of predation on the pelagic microbial food web in this lake, we conducted a series of field experiments manipulating different zooplankton structures in 2 l enclosures. The results showed that the presence of B. michaelseni and rotifers depressed ciliates and nanoflagellates, but did not affect autotrophic picoplankton and total bacteria abundances. In contrast, the presence of Daphnia was decisive in decreasing autotrophic picoplankton abundances. P. sarsi was observed to prey on B. michaelseni copepodites and adults and a weak cascading effect on the microbial fraction could be detected.