SHOALS OF DREISSENA-POLYMORPHA AS BIOPROCESSOR OF SESTON

Mussels of D. polymorpha were collected from mesotrophic lake Parte{ogonek}czyny in which it occurs in form of narrow but very dense shoal. Having transported them to the laboratory live specimens were sorted with respect to size and placed in lake water on artificial substrata made with plexi plates. During the night most of mussels reattached to substrate with byssus threads. The plates covered with mussels were transported to shallow, eutrophic lake Druzno in which D. polymorpha has not been present in recent years. A set of plates and separate plates were exposed in lake water to which a fine fraction of sediment was added. The resulting concentration of suspension was slightly higher than those found during intensive sediment resuspension. It was observed that during first 10-30 minutes of exposure to suspension mussels kept their valves closed, but after this time they were able to continue filtration. The obtained results showed that the relatively high concentration of sediment added to lake seston did not affect clearance capacity of suspension in D. polymorpha and even enhanced it. © 1990 Kluwer Academic Publishers.