Original paper

Settlement pattern of the zebra mussel, Dreissena polymorpha, as a function of depth in Lake Constance

Wacker, Alexander; Von Elert, Eric


Settlement on suitable substrata under favourable environmental conditions is an important factor for a successful recruitment of adult populations of Dreissena polymorpha. Therefore, the pattern of settlement of zebra mussel (Dreissena polymorpha) larvae at different depths was studied in Lake Constance. Maximum densities of larvae and newly settled juvenile mussels were observed at 4 m depth, while only single settlement episodes were recorded at greater depths (15m and 30 m). Temperature fluctuation was used as a surrogate parameter for internal seiches. Biotic and abiotic parameters were subjected to a principal component analysis (PCA). The tight coupling of the internal seiches, larval abundance and settlement at 4-m depth vs. the lack of coupling of the latter two variables at greater depths indicated that water currents transported settling larvae to the substrata at greater depth. Our data suggest that physical factors, such as boundary mixing and internal seiches, should be considered as sources of variability in settlement.