Variation in distribution and biomass of marine benthic algae off Kulien, S Sweden

Abstract

Samples of the macrobenthic flora were collected at 2, 4, 6, 8 and 10 m below mean water level at Kullen, S Sweden. The frequency, length, reproductive pattern and biomass o f the commonest species, and the variations of these with depth and season are discussed. The species composition and the size of the plants indicate that the flora is strongly affected by the brackish environment. Only few species contributed substantially to the total mean biomass (100.1 g dry wt 0.25 m 2 ) : Fucus serratus (56%), Laminaria digitata (7%), L . saccharina (4"/0). Furcellaria hmbricalis (14%), the Phyhphora species (5%) and Chondrus crispus (3%). Species with thin filamentous or sheet-like thalli made up the remaining ca. 11%. The contribution made by this group increased with depth from 1% at 2 m to 48% at 10 m. The mean biomass at each depth was strongly correlated to the irradiance. The seasonal variation in biomass followed that of the irradiance but with a lag. In winter and late summer the growth was also influenced by temperature and nutrient concentrations. The total biomass is delimited by the low and fluctuating salinity in Oresund.