BENTHIC GRAZERS AND SUSPENSION FEEDERS - WHICH ONE ASSUMES THE ENERGETIC DOMINANCE IN KONIGSHAFEN

Size-frequency histograms of biomass, secondary production, respiratio n and energy flow of 4 dominant macrobenthic communities of the intert idal bay of Konigshafen were analysed and compared. In the shallow san dy flats (Nereis-Cosophium-belt [N.C.-belt], seagrass-bed and Arenicol a-flat) a bimodal size-frequency histogram of biomass, secondary produ ction, respiration and energy flow was found with a first peak formed by individuals within a size range of 0.10 to 0.32 mg ash free dry wei ght (AFDW). In this size range, the small prosobranch Hydrobia ulvae w as the dominant species, showing maximal biomass as well as secondary production, respiration and energy now in the seagrass-bed. The second peak of the size-frequency histogram was formed by the polychaete Ner eis diversicolor with individual weights of 10 to 18 mg AFDW in the N. C.-belt, and by Arenicola marina with individual weights of 100 to 562 mg AFDW in both of the other sand flats. Biomass, productivity, respi ration and energy flow of these polychaetes increased from the Nereis- Corophium-belt, to the seagrass-bed, and to the Arenicola-flat. Mussel beds surpassed all other communities in biomass and the functional pa rameters mentioned above. Size-frequency histograms of these parameter s were distinctly unimodal with a maximum at an individual size of 562 to 1000 mg AFDW. This size group was dominated by adult specimens of Mytilus edulis. Averaged over the total area, the size-frequency histo gram of energy now of all intertidal fiats of Konigshafen showed one p eak built by Hydrobia ulvae and a second one, mainly formed by M. edul is. Assuming that up to 10% of the intertidal area is covered by musse l beds, the maximum of the size-specific energy flow will be formed by Mytilus. When only 1% is covered by mussel beds, then the energy flow is dominated by H. ulvae. Both animals represent different trophic ty pes and their dominance in energy now has consequences for the food we b and the carbon flow of the total area. If the energy flow of the mac rozoobenthos of Konigshafen is dominated by M. edulis, then the primar y energy has to be gained from the pelagic primary production and the total ecosystem will be dependent on energy input from the North Sea a nd deeper parts of the adjacent Wadden Sea. In the case of a dominance of H. ulvae, the energy flow of Konigshafen is mainly based on autoch thonous primary production.