LIFE STRATEGIES OF FILAMENTOUS ALGAE IN THE NORTHERN BALTIC PROPER

Short lived filamentous algae are a major component of the rocky-shore macroalgal vegetation of eutrophic waters in the Baltic Sea. They sho w considerable variation in abundance both seasonally and from year to year. In this study the seasonal pattern of growth and reproduction i s documented in six species to outline their life strategies. Five of the species studied were reproductive in summer or autumn, just after a period of active growth. Pilayella littoralis was the only exception . It grew fast in the spring but reproduction was successful only in w inter, when only the basal parts of plants were left. The amount of fi lamentous algae was very low in winter. The only species which survive d the winter period as macroscopic filaments was Ceramium tenuicorne. At least three species, Cladophora glomerata, Dictyosiphon foeniculace us and Ectocarpus siliculosus, relied on microscopic stages to survive the unfavourable winter period. Responses of these filamentous specie s to variations in their physical environment are discussed.