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Development and fate of cyanobacterial blooms in the Baltic

Obiettivo

The objective of the project is to achieve a better understanding of the development of marine phytoplankton blooms, their contribution to primary production in the sea and their role in transport and cycling of elements. The project will specifically contribute to a better understanding of the Baltic Sea ecosystem.


The Baltic Sea is a large water body which has only little exchange with the open ocean. For this reason it represents an excellent system for ecosystem studies, especially with regard to problems related to eutrophication. The Baltic is a brackish sea. Primary productivity is affected by high nutrient input. Although input from the atmosphere (wet and dry deposition) and from land (rivers, run-off), biological nitrogen fixation in the Baltic proper contributes significantly to the nitrogen input. Cyanobacteria such as Nodularia and Aphanizomenon are responsible for the nitrogen fixation. They form heterocysts which is an adaptation for nitrogen fixation in the presence of oxygen. These organisms contain gas vesicles which provide them with buoyancy. Dense water blooms develop every year and scums form when the cyanobacteria float at the surface. Blooms of the heterocystous cyanobacteria are conspicuous but large numbers of picoplanktonic cyanobacteria contribute also significantly to phytoplankton biomass and primary production in the Baltic Sea.

Compared to freshwater blooms marine algal and cyanobacterial blooms have not received much attention. The frequency and density of marine water blooms has recently increased markedly. This is often attributed to increasing pollution of the marine environment, notably the increase of the level of nutrients. However, the changes that currently take place in the marine environment are complex and poorly understood. Primary productivity in the marine environment is generally believed to be nitrogen limited. Nevertheless, biological nitrogen fixation in the marine environment is rare and predominantly attributed to non-heterocystous cyanobacteria. The occurrence of heterocystous cyanobacteria in the Baltic is therefore unexpected and also makes nitrogen limitation of primary production here unlikely.

The project aims at the estimation of the contribution of cyanobacterial phytoplankton to primary production and the specific contribution of nitrogen-fixing and picoplanktonic cyanobacteria. The role of buoyancy adjustment of specific cyanobacterial species in the vertical transport of organic matter (photosynthate) and inorganic compounds (phosphates, iron, micro-nutrients) and in the positioning of these species in the vertical light field and nutrient regime, will be investigated. The participants in the project will also determine the photosynthetic efficiency and quantify biological nitrogen fixation as well as elucidate the specific adaptations that optimize these processes. In order to achieve these goals plankton specialists, taxonomists, ecologists, plant physiologists, microbiologists, biochemists, and molecular biologists from Germany, Italy, The Netherlands, Sweden and the United Kingdom work closely together in this project. Field data are obtained during cruises with the research vessels 'Poseidon' and 'Alkor' of the Institut für Meeresforschung of the University of Kiel, Germany.

Invito a presentare proposte

Data not available

Meccanismo di finanziamento

CSC - Cost-sharing contracts

Coordinatore

Universiteit van Amsterdam
Contributo UE
Nessun dato
Indirizzo
127,Nieuwe Achtergracht
1018 WS Amsterdam
Paesi Bassi

Mostra sulla mappa

Costo totale
Nessun dato

Partecipanti (5)