ALKOR AL544

This practical at sea is intended to integrate physical and biological information along the extended salinity gradient of the Baltic Sea to raise the importance of physical-biological interactions, the structuring effect of the physical environment on bacterio-, phyto- and zooplankton communities and how this relates to the productivity of higher trophic levels such as fish (here ichthyoplankton) and gelatinous macro-zooplankton. Special consideration will be given to observed and expected changes due to global change induced stressors, which can be assessed based on available long term data from the Bornholm Basin. In this context, focus will be devoted to the distribution, dispersal and population development of native and invasive gelatinous maco-zooplankton species along the salinity gradient of the Baltic Sea. This comparative analysis is expected to contribute to the long standing scientific discussion, if jellyfish abundances are increasing or not.