BIOTIC INTERACTIONS OF THE ZOOPLANKTON COMMUNITY OF A SHALLOW, HUMIC LAKE

The objective of this paper was to recognize the predator-prey relatio ns and competitive interactions in the zooplankton community of a shal low, humic Lake Flosek (Great Masurian Lake District). The year to yea r changes in the seasonal pattern and sequence of peak abundance of he rbivore and predatory Crustacea and Rotifera were observed. Zooplankto n in this lake showed also a distinct vertical distribution and more o r less visible diel vertical migrations as well as the horizontal migr ation of Crustacea species between pelagial and near-shore zones of la ke in summer period. The changes of demographic events like the decrea se of mean body size of adults as well as decrease of fecundity along the inshore-offshore transect were also observed. This distinct habita t partition between crustaceans and rotifers can reflect a combined ef fect of food scarcity and predator pressure. Zooplankton of the shallo w Lake Flosek is controlled by the complicate net of feed-back relatio ns, resulting in a rather stable community structure which can explain its rather unsignificant changes in the period of about 20 years afte r the liming of water in this lake.