Germination and anchorage of Enteromorpha spp. in sediments of the Wadden Sea

Abstract

Large quantities of filamentous green algae (Enteromorpha spp.) have regularly occurred on muddy and sandy tidal flats in Königshafen, on the island of Sylt (North Sea), since 1979 - covering the sediments in thick mats during the summer months. While spores of Enteromorpha were encountered in both mud and sand, germling formation was restricted to sand. However, mud snails (Hydrobia ulvae Pennant) were overgrown with small Enteromorpha filaments in both habitats, about 50% of them at a muddy site and 20% at a sandy one. Filaments, several cm in length and still adhering to the snails, became tangled into clusters. At the sandy site, with abundant Arenicola marina L., these clusters slid into the feeding funnels of lugworm burrows; the importance of this secondary anchorage is demonstrated by a field experiment. We suggest that the primary and secondary attachment of Enteromorpha filaments provided by benthic fauna is an essential step in the development of green algal mats on sedimentary tidal flats. © 1993 Biologische Anstalt Helgoland.