Rhodes cold-core cyclonic eddy

Type of feature Depth of permanent nutricline Depth of deep chlorophyll maximum Integrated chlorophyll a (mg nT2) Reference 

The winter values are taken from a year cold enough to induce deep winter mixing. Probably unusually low as a result of active deep winter mixing. 

In winter the pycnocline moves up towards the surface. In a mild winter the pycnocline reaches to within 15-20m of the surface while in a cold winter such as 1991/92 it disappears entirely and LDW reaches the surface. There is then essentially constant temperature and salinity from the surface to at least 1000m depth (Yilmaz, personal communication). During such periods of deep winter mixing, the surface waters have nutrient contents which are, for the Eastern Mediterranean, extremely high with phosphate values of 0.16 pmolkg-1, nitrate of 4.7 pmolkg-1 and silicate of 6-7pmolkg 1 and no nutricline present (Table 4.2). This is an important source of nutrients and productivity to the whole basin. 

However, there are interannual variations caused by the depth and rate of winter mixing. During the exceptionally cold winter of 1991/92 the 3000 m water column at the core of the Rhodes Gyre was vertically mixed from top to bottom, with homogeneous temperature and salinity profiles. At this time, there was relatively low chlorophyll biomass ( 44 mg/m2) and phytoplankton activity (Table 4.2 Edigar Yilmaz, 1996). This cannot be due to nutrient or light limitation since nutrients are present and there are phytoplankton blooms 

In the periphery of the Rhodes Gyre, where the deep winter mixing was less intense, the phytoplankton biomass (in terms of chlorophyll a and particulate organic carbon) and the primary production rate measurements show higher values which are comparable to western concentrations (Ediger Yilmaz, 1996). Very high values of chlorophyll a (238 mg m-2) were observed in a less intense cyclonic feature in the Finike Basin at this time. 

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