Climatic and Eutrophication Effects on the North Aegean Sea Productivity and Anchovy (Engraulis encrasicolus) Stock

Abstract

Climate change is expected to have a strong effect in the Mediterranean Sea [1]. Even though climate projections may be characterised by significant uncertainties, current climate model simulations have all indicated a significant warming in the Mediterranean Sea [2-4]. An increase of sea surface temperature is expected due to global warming, while decreased precipitation and river runoff might potentially result in an increase of salinity with an opposite effect on stratification, particularly in coastal river influenced areas. An increase of stratification may reduce the productivity through reduced enrichment of euphotic zone with deep-water nutrients. On the other hand, increased stratification may influence the North Aegean circulation that is dominated by the Black Sea Water (BSW) pathways and Levantine water inflow Figure 1, as well as the thermohaline circulation that is related to the N. Aegean nutrient balance. In particular, increasing stratification results in a weakened thermohaline circulation characterised by decreased Levantine water inflow and southward export of deep N. Aegean waters, caused by the reduced dense water formation. The decreased export of deep nutrient rich N. Aegean waters result in the slight enrichment of the nutrient pool and primary production in open sea areas [5].