The Baltic Sea constitutes a young ecosystem, which is constantly undergoing changes in response to climate variations and human activities. These changes affect all physical, chemical and biological components of the system as well as their interactions.

The theme focuses on understanding the past to describe the present situation and possibly predict the future behaviour of the Baltic Sea. This includes descriptive and experimental studies, using observations and/or models that aim to better understand the dynamic behaviour of the Baltic Sea, its coastal ecosystems and watersheds. The sessions under this theme will address topical questions such as:

• What can we learn about climate and ecosystem changes in the Baltic Sea region and their variability    during the Holocene from stratigraphic studies?
• How has the Baltic Sea changed over the last century and what is the role of natural versus human-      driven variations?
• How will the Baltic Sea behave in a future warmer climate with changing salinity, less sea ice, less          oxygen, and lower pH?
• Are extreme events and natural hazards becoming the norm and how will this affect the Baltic Sea?
• Will land-sea interactions change in the near future?
• How has the cycling of key elements changed over time and what are their projections for the future?
• How do invasive species affect the ecosystem on the short and long terms?
• Are biological communities becoming more or less complex (diverse, stable etc.) over time?
• How will the Baltic Sea organisms be affected by the future environmental changes?
• Are the expected changes irreversible and do we have early-warning indicators for potential regime        shifts?
• How do changes in the Baltic Sea compare to other ecosystems?