Benthic organism biomass size-spectra in the Baltic sea in relation to the sediment environment

Abstract

Biomass size-spectra of benthic organisms (BBSS) were constructed for 44 stations in three basins of the Baltic Sea: Bothnian Bay, Bothnian Sea, and the Baltic Proper, which represents a salinity gradient from about 3‰ to 18‰, respectively. In addition, BBSS were regrouped and analyzed according to an encompassing sediment environmental variable: Loss of weight on ignition (LOI). LOI correlates with many other sediment environmental variables and can characterize the sedimentary environment in a location. BBSS from the Bothnian Bay were different than those of the Bothnian Sea and Baltic Proper, though BBSS from the latter two basins did not differ from each other. This difference of Bothnian Bay BBSS was indirectly attributed to salinity as it is a region impoverished in both marine and freshwater species; hence individual species size-distributions contribute considerably to the whole resulting in a different BBSS. BBSS grouped according to sediment LeT did not differ from each other. As there were no differences between LeT-grouped size-spectra yet geographical and hence species diversity groupings did differ, it is apparent that the sediment environment is less important than species diversity in determining BBSS patterns in the Baltic Sea. This is in contrast to common environmental explanations for BBSS patterns in other regions.