Coastal productivity in the Baltic Sea  <B>Coastal productivity in the Baltic Sea</B><P><B>Ulrik Kautsky</B><SUP>1</SUP>,<SUP>2</SUP><B> & Hans Kautsky</B><SUP>2</SUP><P> 1.<I> Department of Zoology, Stockholm University, S-106 91 Stockholm, Sweden</I><B></B><BR> 2. <I>Department of Systems Ecology, Stockholm University, S-106 91 Stockholm, Sweden</I><B><P> Abstract</B><BR> The total biomass of macrofauna and flora down to 25 m depth along the Swedish Baltic Sea coast was calculated from quantitative data obtained by scuba diving. Total primary production and respiration were estimated from P:B and R:B ratios and compensated for latitudinal variation in light and temperature during the year. Total biomass in the phytobenthic zone (vegetation and <I>Mytilus</I>-covered bottoms) was 1.1 3108 kg C of plants and 0.8 3108 kg C of animals, most of which were found in the Baltic proper. Biomass was dominated by the perennial brown alga <I>Fucus vesiculosus</I> and the blue mussel <I>Mytilus edulis</I>. The phytobenthic primary production was 5.4 3108.kg C.y1, filamentous algae dominating.<BR> Of the total annual production (plankton + phytobenthos) in the coastal zone, phytobenthic production contributes 12% in the Baltic proper, 23% in the Bothnian Sea and one half in the Bothnian Bay. In the Baltic proper the phytobenthic zone filter feeders had potential to consume 35% of the annual pelagic production equivalent to the carbon sedimentation.<BR> The phytobenthic zone contributes a significant part to the total primary production and carbon turnover in coastal areas and the potential couplings between benthos and the pelagic community seem to be strong. The turnover of carbon in the coastal zone is of the same magnitude as the total carbon deposition in the entire Baltic Sea. This implies that the phytobenthic primary producers and consumers need much more attention in future assessments of the flux of matter between land and open seas.<I><P> Keywords</I>: primary production, community metabolism, model, ecosystem, energy flow, phytobenthos, energetics, respiration, <I>Fucus vesiculosus</I>, <I>Mytilus edulis</I>.<P>