The role and importance of gelatinous zooplankton in the Baltic Sea, with special emphasis on climate change

Human-induced stresses like habitat alteration and climate change may cause changes in fragile marine environments. The pelagic zooplankton is important component of the marine ecosystem as an efficient energy transporter from primary producers to the higher levels in the food web. During the last decade gelatinous zooplankton have started to increase and have become dominant members of the zooplankton community in many areas of the world, including the Baltic Sea. Despite the fact that the importance of gelatinous zooplankton in marine systems is increasingly being recognized, very little knowledge exists of these species.

The Arctic ctenophore Mertensia ovum was recently recognized for the first time in the Baltic Sea, and has never before been reported to occur in brackish waters. Despite of the uncertainties in the invader status of this species it may have a potential to impact the food web, since its abundances have markedly increased in the Gulf of Finland recently. The prey preferences of the Baltic M. ovum as well as effects on plankton and planktivores are unknown. The only studies done on M. ovum predatory abilities are from the Arctic and they clearly show that it is a strong grazer on copepods. Thus we hypothesize that M. ovum may affect the Baltic food web as well through increased predation pressure on plankton.

This study will combine traditional sampling and community structure analyses, data analyses of the time-series data of plankton together with modern laboratory experiments and molecular methods. The goals are: A) To study the role of ctenophores in the Arctic Ocean and in the Baltic Sea. B) To study the long-term changes in the zooplankton communities. C) Estimate how the predicted climate change will affect plankton and ctenophore populations. Further more; the overall goal of this project is to indicate that more emphasis should be put into the gelatinous part of the plankton community to be able to adequately model the community interactions and changes.