PHYTOPIGMENTS AND FATTY-ACIDS AS MOLECULAR MARKERS FOR THE QUALITY OFNEAR-BOTTOM PARTICULATE ORGANIC-MATTER IN THE NORTH-SEA

In February, May and August 1994, four stations in the North Sea (viz. at the Broad Fourteens, Frisian Front, German Eight and Skagerrak) we re visited to sample near-bottom particulate organic matter. Samples, taken by means of a pump, a sediment trap and a sediment recorder, wer e analysed on organic carbon, total nitrogen, phytopigments and fatty acids. These molecular markers were used to describe the nature and qu ality of the organic particles in the near-bottom water. Principal com ponent analysis showed chlorophyll a, phaeopigments and fatty acids to be useful markers for the quality of organic matter and yield complem entary information. The quality of the near-bottom particles appeared to be related to the local hydrography and depositional circumstances. The Broad Fourteens station, a non-depositional sandy site along the Dutch coast, showed organic particles to be relatively fresh, little i nfluenced by resuspended sedimentary material. Near-bottom organic par ticles on this site contained relatively high shares of chlorophyll a and polyunsaturated fatty acids, characteristic of algal matter. On th e other hand the particulate organic material on the two depositional locations, the Frisian Front and the German Eight stations, was influe nced by resuspension of sedimentary organic particles poor in pigments and fatty acids. Amounts of carbon trapped in the near-bottom environ ment at the Skagerrak station were lower than expected from the litera ture.