Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Baltic Sea cyanobacteria

The project Baltic Sea cyanobacteria (BASIC) is an investigation of the structure and dynamics of water blooms of cyanobacteria in the Baltic Sea with the aim of predicting its response to a changing environment. The cyanobacterial community of the Baltic Sea can roughly be distinguished in a group of morphological large, filamentous species and in the extremely small picoplanktonic cyanobacteria. The former is composed of diazotrophic species that are responsible for 25% of the nitrogen input in the Baltic Sea. They can form aggregates, and have gas vesicles which provide them with buoyancy, produce bad odour, discolour the water, degrade the water quality and may be extremely toxic. The development and occurrence of these waterblooms is poorly understood. Preliminary results indicated that iron is the limiting nutrient. The surface accumulations of these cyanobacteria represent often only some 10% of the total biomass of this group of organisms with most distributed in the water column. However picoplanktonic cyanobacteria may represent up to 80% of the cyanobacterial biomass and may be responsible for the same amount of primary productivity. Preliminary results indicate that growth of these species is limited by nitrogen with 10-20% of the nitrogen fixed by the diazotrophic species transferred to picoplankton. Hence, these cyanobacteria are indirectly also limited by iron. The picoplanktonic cyanobacteria do not fix nitrogen, do not possess gas vesicles and do not form large aggregates. Currently it is not known whether they produce toxins. The genetic diversity with the picocyanobacteria was investigated as well as that of the diazotrophic species Nodularia species. It was demonstrated that at least two distinctly different genotypes of this cyanobacterium were present. They occurred in equal numbers but were not distributed uniformly. A better understanding of the initiation and the temporal and spatial patchiness of cyanobacterial blooms in the water of the Baltic Sea was gained and is being used to develop a tool with which predictions can be made regarding the (local) risks caused by toxin production and regarding contributions of new nitrogen and carbon inputs into the basin.

Reported by

Nederlands Instituut voor Oecologisch Koninklijke Nederlandse Akademie van Wetenschappen Onderzoek
Korringaweg 7
4401 NT Yerseke
Netherlands
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