Carstensen, J., Helminen, U., Heiskanen, A.-S.. Typology as a structuring mechanism for phytoplankton composition in the Baltic Sea. In: Schernewski, G., Wielgat, M. (eds.). Baltic Sea Typology. Coastline Reports (4), pp. 55-64. EUCC - The Coastal Union, Leiden, 2004.
Phytoplankton composition is a biological quality element to be used for ecological classification within the Water Framework Directive. Seasonal proportions of diatoms, dinoflagellates, cyanobacteria and chlorophytes calculated from species-specific phytoplankton biovolumes sampled in 38 water bodies within the Baltic Sea were investigated to determine if the typology, defined by salinity, depth and retention time regimes, provided a useful separation of water bodies into groups for intercomparison of phytoplankton compositions. Variations in the phytoplankton composition could be significantly related to a combination of salinity and depth regimes. The significance of retention time as structuring mechanisms could not be properly assessed due to relatively few water bodies with long retention times. Cyanobacteria and chlorophytes were almost completely absent in the more saline and turbulent waters of the Kattegat and Belt Sea, whereas the proportion of diatoms and dinoflagellates generally increased with salinity. The significance of the depth regime relied entirely on few water bodies in the German part of the Baltic Proper that had a phytoplankton composition deviating substantially from other water bodies with similar salinity. Consequently, salinity ranges may provide a useful typology definition for segregating water bodies into distinct groups, however, other characteristics, not exploited in this study, need to be included as well to be able to distinguish different water body types based on their phytoplankton composition.
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