Tracing hypoxia during warm periods in the Baltic Sea region using synchrotron X-ray spectroscopy and plasma analytical methods
One of the largest marine environmental challenges presently is deoxygenation, i.e. decreasing dissolved oxygen concentrations in the world oceans, caused especially by increased temperature and stratification. In coastal zones, additional processes such as human induced eutrophication as well as circulation changes are also major contributors to the decrease in oxygen concentration in bottom waters and expansion of hypoxia ([O2 <2mg/l].
The present- day anthropogenically-induced environmental changes in coastal settings have created a need for a context to understand the severity and potential outcomes of such changes. This context can be derived from paleoenvironmental records during periods when comparable events happened in the past. In the Baltic Sea region, several warm periods have occurred since the most recent glaciation. There is evidence that these periods in the Baltic were also marked by deoxygenation. Quantitative environmental reconstructions from these periods can offer important examples of rates of warming and severity of hypoxia as well as associated ecosystem changes and provide important boundaries for evaluating the magnitude of potential future changes.