SUSPENDED PARTICULATE MATTER GEOCHEMISTRY OF THE ALEXANDROUPOLIS GULF, NORTHEASTERN AEGEAN SEA

Alexandroupolis Gulf is the recipient of the freshwater of the Evros River, the largest river system (in terms of water supply) discharging into Eastern Mediterranean (NE Aegean Sea) after the Danube River. Suspended particulate matter (SPM) samples were collected from various depths, at 14 stations in Alexandroupolis Gulf during four periods (June 1998, September 1998, February 1999 and March 2000) in order to examine the organic carbon, nitrogen and trace elements contents. Although the values of the various parameters fluctuate strongly according to the sampling period, there is a general trend of higher organic carbon values in the deeper sectors of the water column. The seasonally adjustable seawater circulation in the gulf seems to be the regulative factor of the surficial distribution of organic carbon and nitrogen, while calcium carbonate content seems to be connected with the presence of carbonate marine organisms and the seasonal pattern of phytoplankton growth. Moreover, according to C:N ratio values, the origin of carbon in the SPM of the gulf is mainly marine and controlled by marine bacteria, phytoplankton and microalgae abundance. In addition, although the trace element values in the Alexandroupolis Gulf SPM are lower than those recorded in heavily polluted Greek areas, the calculation of Enrichment Factor derives high values in Cu (Enrichment Factor, EF: 37), Cd (EF: 33), Co (EF: 23), Zn (EF: 22), Pb (EF: 13) and Cr (EF: 8), while Ni seems to be unaffected by any human influence (EF: 1).