Plant pigments as biomarkers of organic matter sources in sediments and coastal waters of Cyprus (eastern Mediterranean)

Plant pigments (chlorophylls and cartenoids) and radionuclides (Ra-226 and Pb-210) were measured in the coastal waters and sediments off the coast of Cyprus (eastern Mediterranean), for the first time, in June and July 1993. Some of the lowest concentrations of chlorophyll a (10-90 ng l(-1)) were found in these highly oliogotrophic waters. Based on the presence of chlorophyll b and zeaxanthin, it appeared that chlorophytes, cyanobacteria, and prochlorophytes were the dominant phytoplankton classes. The phytoplankton assemblage off the coast of Cyprus was not very different when compared to the deeper regions of the eastern Mediterranean. However, there were significantly higher concentrations of pigments in sediments principally due to seagrasses and macroalgae. In fact the Red Sea migrant Caulerpa racemosa appears to be expanding its areal coverage along the coastline; it remains to be tested whether this is related to enhanced nutrient inputs or to inherent differences in the life-history characteristics of this migrant vs. native species. The very low sedimentation rates observed at all stations (0.38-0.78 mm year(-1)) further suggested that input from the water column to the sediments was minimal. The land-margin effects of Cyprus on the surrounding oligotrophic waters of the eastern Mediterranean appeared to only affect the composition and distribution of benthic macrophytes, with very little change in the phytoplankton assemblages. (C) 1996 Academic Press Limited