Cyanobacteria and microalgae are the main representatives of phytoplankton. In the brackish water system of the Baltic Sea, they are exposed to varying salinities and nutrients. Therefore, the amount of external salt or the availability of nutrients represents one of the main environmental factors for the distribution of these organisms on Earth. For salt acclimation, cyanobacteria and microalgae use the so-called salt-out strategy when they are exposed to high or varying salinities. This acclimation strategy includes two main features: (i) keeping rather low and unchanged internal concentrations of inorganic ions via active transport mechanisms to avoid toxic effects on metabolic activities, and (ii) accumulating low molecular hydrophilic organic compounds (compatible solutes) in high intracellular amounts to make the cytoplasm hyperosmotic toward the external medium ensuring water uptake and positive turgor. Molecular mechanisms for high salt acclimation among microalgae are presented and discussed. Furthermore, the amount of available phosphate is often regarded as limiting factor in brackish waters. Especially during the formation of so-called cyanobacterial blooms in the Baltic Sea during summer, P limitation is discussed as one potential triggering factor. The molecular acclimation of the toxic cyanobacterium Nodularia spumigena towards P limitation will be discussed. This knowledge will not only promote the understanding of phytoplankton successions but will contribute to future efforts using cyanobacteria and microalgae in mass cultivations.
Baltic TRANSCOAST Seminar Room (Room 113)
Albert-Einstein-Straße 21
18059 Rostock