BALTOX

Algal toxins in the Baltic Sea paleo-record

Project Description

Pervasive and recurring harmful algal blooms (HABs) are symptomatic of anthropogenic imbalance of ocean nutrient cycles and climate change. These blooms can be harmful to ocean health not only because they cause oxygen-deficient dead zones but also because some algae including diatoms, dinoflagellates, and cyanobacteria, produce organic compounds that are toxic to other algae and higher trophic levels. Algal toxins impact not only aquatic food chains but are directly detrimental to human health. HABs are thought to increase in frequency and intensity under global warming conditions, particularly in the Baltic Sea. However, these projections are mostly derived from laboratory cultures testing changes in single parameters or from models. In the modern ocean, only some algae produce toxins and thus it is unclear whether an increase in algal blooms also results in an increase of toxic algae and whether the toxicity of blooms is directly coupled to climate change. The key to understanding the coupling of climate and HABs may lie in the geologic record of algal blooms but clear links between HABs and past climatic events have not been established but could prove to be instrumental for predicting future changes in HABs.

In this project, we will study whether toxin production by HABs was coupled to climate change, specifically ocean temperature, in the past. To extract this information from the geologic record, we will develop a new analytical method for the analysis of algal toxins from sediments. We will apply this method to sediment cores and water samples from Kiel Bay in the Baltic Sea to reconstruct the occurrence of toxic algae in relation to past climate change. The sediment cores span the last 100 years at interannual resolution and thus allow high-resolution reconstructions of algal blooms, toxins, and climate.