Role of benthic macroalgae in regulating macrozoobenthic assemblages in the Vainameri (north-eastern Baltic Sea)

The relationships between the abundance and biomass structure of invertebrate assemblages and environmental variables were sought by using multivariate statistics. Sediment type explained the biggest part of the variation in invertebrate assemblages in the deeper areas and dominant macroalgae in the shallower areas. Additionally, the loose-lying macroalgae, Furcellaria lumbricalis, contributed to the increase in macrozoobenthos densities in the deeper parts of the Vainameri by offering secondary substrate for true hard bottom invertebrates. The infauna below the algal mat was poor when compared to the sediments in unvegetated areas. On the other hand, the introduced polychaete, Marenzelleria viridis, was found only under the mat of F. lumbricalis and the biomass of the polychaete increased with the coverage of F. lumbricalis.