Chloropigments a in sediments of the Gulf of Gdańsk deposited during the last 4000 years as indicators of eutrophication and climate change

The occurrence of chlorophyll a derivatives in a sediment core from the Gulf of Gdańsk (southern Baltic Sea) was investigated. The core (380 cm long) was taken in the area with the highest sedimentation rate. Ninety-five sub-samples of the core were analysed for their pigment and organic carbon contents. Selected sections of the core were 14C-dated and analysed for granulometry. The results of the study are in agreement with previous observations for Eastern Gotland Basin sediments that there are greater quantities of chloropigments in the deeper layers than in more recent sediments taken from the same site. Secondary diagenesis products, pyrophaeophytin a and steryl chlorin esters, are taken here as indicators of diagenetic processes under anoxic conditions and hence of sediment age. These results endorse earlier hypotheses that past eutrophication in the Baltic has occurred at a higher level than that observed nowadays, and that climate may be a more important factor relative to anthropogenic impacts in influencing the combination of primary production and pigment preservation in sediments.