Studies of old sediments in the Baltic Sea indicate that eutrophication occurred with different intensity during the last two millennia, and not only in recent times. Cyanobacteria blooms might have occurred as early as 7000 years BC. Knowledge about natural toxicity of these sediments is absent, though both algal toxins and natural dioxins could have been produced during these episodes. Thus, climatic change may thereby impact human health and the marine environment. Aim of the study is to study climate change effects in the sedimentary record, and connect it to indicators of the health of the marine environment archived in the sediments. Phytoplankton structure and biomass belong to the main indicators of the health of the marine environment. Phytoplankton population depends on climate factors, hydrodynamics and contaminants occurring in an ecosystem. These organisms have an impact on the fate and transport of contaminants in the sea and the anthropogenic toxicity. Some phytoplankton strains can release natural toxins to the environment. The aim of the project will be realized by studying sediment indicators of natural and anthropogenic indicators of ecotoxicity in relation to different geological sediment proxies. Recent and old - formed in historical times - sediments of coastal locations of different climate, hydrology and contaminant burial history will be analysed and compared: Gulf of Gdańsk (southern Baltic) and Oslofjord/Drammensfjord as well as in the arctic region (Norway). Analysis of multi parameter sets will indicate sediment variability connected to different climatic conditions for the studied areas, as well as threats of release of natural and anthropogenic toxicity as a result of climate change. This research will increase our knowledge base and be and important contribution to the implementation of Marine Strategy Framework Directive and other management decisions related to the marine environment.