Linking nutrient loading, local abiotic variables, richness and biomasses of macrophytes, and associated invertebrate species in the north- eastern Baltic Sea

Abstract. We studied relationships between nutrient loading, local abiotic variables, richness and biomasses of macrophytes, and associated invertebrate species in the north-eastern Baltic Sea. The study showed that nutrient load strongly correlated to the richness and biomass of macroalgal and invertebrate species and functions and often interacted with local abiotic variables such as salinity and depth. Generally elevated nutrient loads increased the species richness of macrophytes and benthic invertebrates and the biomass of annual macroalgae and of the majority of invertebrate feeding groups, but reduced the biomass of perennial macroalgae. The study also showed that the effect of nutrient loading was scale-specific, i.e. different responses to nutrients were observed at water-body and gulf scales. The biomass of the majority of species and functions was a function of the gulf-scale nutrient loading whereas the variability of annual algae and chironomidae reflected changes in the water-body level nutrient loading.