Climatic and hydrological controls over the zoobenthos in a southern Baltic coastal lagoon

In a four-year-long (1985–1988) study of macro- and meiobenthos of the Szczecin Lagoon, a eutrophic and polluted coastal water body directly connected with the southern Baltic Sea, peculiar interannual dynamics of variables related to abundance was observed. The interannual component of variability was stronger than fine-scale seasonal dynamics. The interannual variations followed a trend whereby abundance of meio- and macrobenthos as well as biomass of the latter was high in 1985, dropped in 1986 and 1987, and rose again in 1988. As the trend could not be explained by local environmental data, explanation was sought by invoking wider-scale climatic and hydrological processes. Data for severity of winters preceding each year of study as well as trends in atmospheric circulation patterns, wind regimes, river runoff characteristics, and near-bottom conductance (used as a proxy for seawater intrusions into the lagoon) were compared to seasonal anomalies in meiobenthic abundance as well as in macrobenthic abundance and biomass. The seasonal mean meiobenthic log abundance anomalies produced no significant correlation with any of the variables tested. In contrast, the seasonal mean log macrobenthos abundance and biomass anomalies were significantly negatively correlated with winter severity proxies (mean winter temperature and cold sum) and flow rate determined with time lags generally longer than one month. The results provide indication of differences in responses of meio- and macrobenthic communities to climatic (winter severity) and hydrological changes, the long-term effects being visible primarily within the macrobenthos. However, establishing sound causal relationships requires longer time-series of data.