engleski

Overflow effect on the dynamics of the rotifer community in cascade lake systems

Many recent studies have been concerned with the rotifer life cycle in relation to changes of abiotic environmental conditions (PAULI 1990), predatory pressure (CHRISTOFFERSON et al. 1993, DUMONT et al. 1994), competition (GILBERT 1985, SARMA et al. 1996) and availability of food (HESSEN 1992, ROTHHAUPT 1995). In karstic standing waters, in cascade hydrosystems especially, these ecological interactions are very complex and insufficiently known. The objective of this study was to determine the overflow effect, an important factor influencing temporal changes in rotifer density and their trophic structure in the two greatest lakes of the cascade hydosystem of Plitvice located in the karstic Dinarid area, consisting of 16 connected lakes. Our hypothesis was based on the fact that during summer thermal stratification, the epilimnetic water of an upstream lake, impoverished in nutrients by phytoplankton activity, flows over the barriers, and in downstream lakes influences the seasonal dynamics of the phytoplankton that constitute the main food source for rotifers. Therefore we hypothesised that in downstream lakes the seasonal cycle of rotifer populations, the most abundant component of the zooplankton, would be influenced by plankton activity in the upstream lakes.

rotifers ; karstic lakes ; trophic structure

nije evidentirano