Zebra mussels with a triangular chamber are the most common representatives of the zoobenthos in Lake Peipus: their biomass here is twenty times larger than the rest of the total of about five hundred species inhabiting the bottom of the lake. It is precisely because of the abundance of zebra mussels that we see large flocks of diving ducks on the lake during the migration of birds. Even the greater scaups (in the picture) and tufted ducks sometimes form giant clusters.

The zebra mussel is an alien species for Lake Peipus. It probably arrived here attached to boats from the Caspian and Black Sea regions, moving along the Velikaya River. Due to its large number, the zebra mussel is an important purifier of the lake water.