Effects of trophic conditions on benthic macrofauna in the vicinity of the River Swina mouth (Pomeranian Bay; Southern Baltic Sea)

The export of phytal material from the eutrophic Szczecin Lagoon into the Pomeranian Bay creates excellent trophic conditions for the local benthic fauna in the vicinity of the mouth of the river Świna, where the bottom macrofauna is abundant but highly variable. The changes in the bottom macrofauna biomass of selected taxa, chlorophyll a and nutrient concentrations were tested for associations. The biomasses of selected taxa varied in significant concordance, which suggests that these changes have common causes. Despite the importance of trophic enrichment to faunal abundance, no relationships between faunal biomass and chlorophyll a concentration changes were established. The presence of organic matter enables macrofauna to attain a high biomass, but population fluctuations are controlled by numerous factors. The significant relationship between the changes in the annual average phosphate levels and chlorophyll a concentrations in the Szczecin Lagoon indicates the importance of this nutrient to primary production processes in the Lagoon and to the trophic conditions for benthic macrofauna in the vicinity of the Świna mouth.