We use laboratory experiments to determine the environmental conditions under which the microalga Prymnesium parvum can grow on massive scale and when it produces its toxins, the so-called prymnesins. We are also investigating the dose-dependent effects of prymnesins on the early life stages of fish such as sturgeon as well as on mussels and zooplankton. In this way, we want to determine risk areas of water pollution in which algal blooms can affect organisms.