On August 13, 2026, the research vessel “Elisabeth Mann Borgese (EMB)” departed from Rostock on Expedition EMB401. On board: a 13-people team of researchers from the IOW, the Alfred-Wegener-Institute (Helmholtz Center for Polar and Marine Research, AWI), the Institute for Chemistry and Biology of the Marine Environment (ICBM, Oldenburg, Germany), the University of Warsaw (Poland), Linnaeus University (Kalmar, Sweden), and the Marine and Freshwater Research Institute (Reykjavík, Iceland). The main objective of the expedition is to identify areas at risk for harmful algal blooms.

The EMB401 expedition is an essential component of the project “BiodivGesundheit: Assessment of the Effect of Novel Harmful Algal Bloom (HAB) Species in the Baltic Sea (HABBAL),” which is funded by the Federal Ministry of Research, Technology and Space (BMFTR). The course takes the ship from Rostock through Danish waters to the Skagerrak, back along the Swedish coast, then past Rügen, along the Polish coast to Gdańsk, from Gdańsk northward toward Gotland, around Gotland, past Öland and Bornholm, and then back to Rostock. During the 18-day research cruise, led by IOW biologist Ingrid Sassenhagen, the team will investigate, among other things, the distribution of the harmful algal species Alexandrium pseudogonyaulax and Prymnesium parvum and their dormancy stages.

Both algae species produce toxic substances and, when they occur in massive quantities as part of so-called algal blooms, can lead to fish kills and shellfish poisoning. These poisonings are detrimental to both tourism and the fishing industry. For example, if the affected shellfish are consumed by humans, the latter can become seriously ill. During the expedition, the spread of algae will be studied using a combination of different methods. First, the levels of toxic substances (known as phycotoxins) produced by the algae will be measured. In addition, the algae will be examined using advanced microscopy and identified based on their genetic sequences (DNA).

Chief scientist Ingrid Sassenhagen explains that toxic algae species are spreading further and further into the Baltic Sea and pose a potential health risk to humans and the environment. She adds: “On this expedition, we want to investigate the distribution of certain algae species that have only been observed occasionally so far, and for the first time, we also have the opportunity to detect their toxins. Unlike on this expedition, the algal species Prymnesium parvum is rarely detected in purely microscopic monitoring efforts due to its small size.”

At the same time, genetic methods (known as metabarcoding) are used to assess the diversity of the plankton community (phytoplankton and zooplankton) as well as that of fish. Phytoplankton refers to microscopic algae and certain bacteria (known as cyanobacteria), while zooplankton encompasses animals such as small crustaceans and fish larvae. By monitoring these organisms, the study aims to investigate the influence of biodiversity on the occurrence of harmful algal species. It also seeks to determine which organisms might suffer from the presence of these algae and their toxins. To answer this question, the researchers will conduct experiments in which they introduce harmful algal species (with a specific known toxin content) into a naturally occurring plankton community and analyze the resulting effects. In addition, experiments will be conducted aboard the EMB to analyze the effects of toxic cyanobacterial blooms on the Baltic Sea food web. Parallel to the expedition, other researchers in the collaborative project are extracting and purifying the toxins from the algal species Prymnesium parvum and Alexandrium pseudogonyaulax in the laboratory. These toxin extracts are then used to investigate the interactions between algal toxins and environmental factors such as heat stress and oxygen depletion with fish respiration, as well as the effects of algal toxins on human and fish cell lines. The research findings from this project will make it possible to better assess the future risk of algal blooms in the Baltic Sea.