Water mass properties and chemical characteristics in the Saros Gulf, Northeast Aegean Sea (Eastern Mediterranean)

Abstract

This work is a description of the water masses and chemical properties in the Northeast (NE) Aegean Sea, a region of recently renewed interest with respect to the hydrology of the Eastern Mediterranean Basin. Analysis of hydrological data from the study area reveals the presence of three water masses: The 20–40 m thick surface layer is occupied mainly by Black Sea Water, BSW, modified on its way through the Bosphorus, the Marmara Sea and the Dardanelles. Below the surface layer there is warm and highly saline water originating from the South Aegean and the Levantine basins, Levantine Intermediate Water (LIW), extending down to 350–400 m depth. Below this layer, the deeper than 400 m basins of the North Aegean contain locally formed, very dense water with different Potential temperature–Salinity characteristics at each sub-basin and called North Aegean Deep Water (NADW). Evidence of temperature-controlled dense water formation of the Gulf of Saros, in the NE Aegean was reported in January 2002. The nutrient concentrations varied between nitrate + nitrite = 0.19–0.37 µM, phosphate = 0.01–0.02 µM and silicate = 0.7–1.1 µM for the surface layer (BSW) during sampling periods. Dissolved nutrient concentrations in the NADW were: 1.7–3.7 µM for NO 3 + NO 2, 0.08–0.17 µM for PO 4 and 2.7–4.2 µM for silicate. During winter, relatively high nutrient levels are observed in the surface layers of the NE Aegean Sea, whilst phosphate and nitrates decrease in summer.