DEVELOPMENT OF THE ZEBRA MUSSEL, DREISSENA POLYMORPHA (PALL.), POPULATION IN A HEATED LAKES ECOSYSTEM. II. LIFE STRATEGY

The mechanisms by which the zebra mussel, Dreissena polymorpha (Pall.), populations form and settle in the thermally and hydrodynamically varied ecosystem of the Konin heated lakes (Poland) were studied. The stability of the populations inhabiting the lotic and lentic environments of the lakes stemmed from their exploitation of better habitat conditions for survival, which was manifested in the effective settling of larvae on substrata, an even sex ratio, higher survival, and better condition and growth rates (strategy K). In lotic and lentic habitats that were heated intensely, unstable populations were noted with a higher share of females, a shorter life span, and lower individual maximum weight. The survival of these populations in these habitats was possible thanks to increased reproductive potential, including a larger share of females and an increased spawning cycle (strategy r). Under stressful conditions, including long-term, elevated water temperatures (> 28 degree C), mass mortality of these mussels could occur in these habitats and the area that they inhabit throughout the system could shrink