Seasonal variations of vegetation patterns and biomass constituents in the rocky eulittoral of Helgoland

Abstract

Seasonal changes in vegetation patterns and biomass of benthic algae were recorded over a 14-month period in the rocky eulittoral of the North Sea island of Helgoland. The area is characterized by the dominance ofFucus serratus throughout most of the eulittoral and this is reflected in higher biomass ofF. serratus ranged seasonally from 4.3 kg to 15 kg m−2 in the center of its extensive distribution. Biomass was also recorded monthly, when the plants were present, forBlidingia spp.,Enteromorpha spp.,Ulva lactuca, Fucus spiralis, F. vesiculosus, Porphyra linearis, P. umbilicalis, Chondrus crispus, Corallina officinalis, Dumontia incrassata, Petalonia fascia, P. zosterifolia andScytosiphon lomentaria. New generations of several species which reappeared after a destructive winter storm showed a higher protein content than in the previous year. The winter and early spring flora of Helgoland shows several resemblances in species composition to the summer flora of Scandinavia.