Climate change and human activities are leading to increasingly frequent and intense extreme events such as storms, floods and heatwaves. These events have a serious impact on coastal and marine ecosystems.
 
In particular, rising water temperatures as a result of heatwaves can increasingly favor the mass occurrence of microorganisms in the North and Baltic Seas. This sudden appearance of bacteria and algal blooms is similar to that in tropical regions. Bacteria such as vibrios, which rarely occur at moderate temperatures, could multiply explosively at water temperatures above 22 degrees Celsius - a scenario that is becoming more likely due to climate change. It is also assumed that the occurrence of cyanobacteria and hypoxia will increase. Some groups of bacteria and algae are capable of producing toxins under suitable conditions, which can have an impact on ecosystems and humans. These biological hazards could have an impact on human health, specific economic sectors such as fishing or tourism, and the marine ecosystem as a result of their proliferation.
 
It is crucial to promote the development of reliable forecasting models and early warning systems so that these risks can be identified and counteracted in good time in order to ensure the long-term protection of ecosystems and society.