Nutritional condition of female Calanus euxinus from cyclonic and anticyclonic regions of the Black Sea

Abstract

The content and composition of lipids in Calanus euxinus females were studied in cyclonic and anticyclonic regions in the southern Black Sea during the period of persistent density stratification (September 1996). The lipid content of C. euxinus from cyclonic regions was greater than of individuals from anticyclonic regions (average 101.9 and 58.8 μg ind. -1 , respectively). Total lipid content (mainly wax esters, 70 to 72 %, and triacylglycerols, 8 to 13 %) of female C. euxinus was correlated with chlorophyll a (chl a) (mean integrated concentration) (r = 0.92, p < 0.005). The high correlation with chl a was shown also for wax ester content, used as a long-term index of food supply (r = 0.89, p < 0.05). The correlation between triacylglycerol content (a short-term index) and chl a was not significant (r = 0.66, p < 0.2). In cyclonic regions the mean integrated chl a concentration (0.38 mg m -3 ) (as an indicator of phytoplankton food biomass) was 1.7-fold higher than in anticyclonic areas. The same trend occurred for mean integrated concentrations of nitrate and phosphate (0.996 and 0.299 μM in cyclonic and 0.438 and 0.061 μM in anticyclonic regions, respectively) in the chl a containing layer. Thus, conditions for total primary productivity in cyclonic regions were more favorable than in anticyclonic ones. This was consistent with lipid levels in female C. euxinus.