Biomarkers in upper Holocene eastern North Sea and Wadden Sea sediments

Total extracts of sediment cores from five different stations in the North Sea and Wadden Sea were analysed for their biomarker composition. Only sediments of the Skagerrak contained significant amounts of marine biomarkers (mainly alkenones), other sites contained predominantly terrestrial biomarkers. Bioturbation in the Skagerrak is, however, far too high to determine sea surface temperature (SST) changes within short time intervals. These results indicate that biomarkers contained in these sediments are not useful to reconstruct climate fluctuations during the upper Holocene. High amounts of alpha-, beta- and omega -hydroxy fatty acids as well as small amounts of alpha, beta -dihydroxy fatty acids were released from the insoluble organic material of the sediments from the Wadden Sea station, indicating a significant input of the eelgrass Zostera marina. This was confirmed by microscopic observations. This is the first time the alpha,beta -dihydroxy fatty acids have been found in a sediment core and they have proven to be potential biomarkers for these seagrass species. (C) 2000 Elsevier Science Ltd. All rights reserved.