Interaction between pelagial and benthal during autumn in Kiel Bight. II. benthic activity and chemical composition of organic matter

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Abstract
Benthic responses to a settling Ceratium bloom during October and to a diatom bloom, sedimenting as late as early December were followed in western Kiel Bight (Baltic Sea). The Ceratium bloom was mixed into the sediment (1 mm · d−1) and caused ATP-biomass increases down to 6–7 cm sediment depth. This bloom was completely consumed. The diatom bloom did not increase benthic activity and was not utilized. This surprising result is explained by insufficient incorporation of the cells into the sediment, due to a change in the macrofauna population (decreasing number of Diastylis rathkei) and to physical conditions in the water column. Budget calculations demonstrate that the settling Ceratium bloom increased metabolism about one third over the pre-bloom level which was based on stored organic material in the sediment. The results also demonstrate differences in timing of pelagic-benthic couplings.