Temporal evolution of physical and chemical characteristics of the water column in the Easternmost Levantine basin (Eastern Mediterranean Sea) from 2002 to 2010

Abstract

The continuing effect of the Eastern Mediterranean Transient event on the distribution of physical and chemical parameters in the Easternmost Levantine basin was documented from 2002 to 2010 in the open sea and at the continental slope. By mid-2002, the deep waters had already changed, exhibiting a mid-depth layer, the old Adriatic Deep Water (ADWo), with minimum salinity, temperature (MinSal/T), minimum dissolved oxygen (MinOx) and maximum nutrient (MaxNut) concentrations above the younger Cretan Sea Ouflow water. MinSal/T values at the ADWo increased from 2002 to 2010, the depth range narrowed, shallowed and was eroded. The maximum silicic acid layer (>9μmolkg−1) was positioned with the MinSal/T, while the MinOx and maximum nitrate and phosphate layers (<175, >5.5 and >0.2μmolkg−1, respectively) were shallower (by up to 500m) due to chemical oxidation of organic matter at the upper layers. Nutrient concentrations at the base of the nutricline increased with time, concurrently with a widening and shallowing of the deep chlorophyll-a maximum layer and increase in concentration. Since 2008 at the slope and 2010 at the open sea, chlorophyll-a concentrations increased also at and near the surface, indicating a possible change in the phytoplankton community. A gradual increase in salinity at the upper layers was detected since 2006.