Seasonal changes in abundance, lipid and fatty acid composition of Calanus euxinus in the South-eastern Black Sea

Abstract

Seasonal changes in abundance, lipid and fatty acid composition of Calanus euxinus Hulsemann, 1991 were analysed monthly during the period from March 2012 to February 2013. The highest abundance of C. euxinus was recorded in February (847 ind. m(-3)) during the sampling period. Female and male C. euxinus peaked in February (587 ind. m(3), 169 ind. m-3, respectively). However, copepodites peaked in November (107 ind. m(-3)). Average total lipid content was determined as percentage (\%) and per individual (mg ind(-1)). It was proportionally highest in February (7.03\%) and lowest in September (3.02\%). However, average lipid content per individual was highest in February (0.11 mg ind(-1)) and lowest in September and November (0.04 mg ind(-1)). Major fatty acids in C. euxinus were identified as 16: 0, 16: 1 n(-7), EPA and DHA. Sigma SSFA, Sigma SMUFA, Sigma SPUFA and Sigma SHUFA were observed to be correlated with temperature. SSFA and Sigma SMUFA increased with the rise in temperature (r(2)= 0.74, r(2)= 0.73, p< 0.05, respectively) whereas Sigma SPUFA and Sigma SHUFA increased as temperature decreased (r(2)=-0.73, r2=-0.80, respectively, p< 0.05). Additionally, while Sigma SPUFA and Sigma SHUFA increased (r(2)= 0.61, r(2)=-0.68, respectively, p< 0.05), Sigma SMUFA decreased (r(2)=-0.68, p< 0.05) as chlorophyll-a increased. It was observed that the degree of unsaturation increased as temperature decreased. Results of the study revealed that C. euxinus has rich lipid content as well as fatty acid composition and it plays an important role in the South-eastern Black Sea ecosystem functionalities especially having key role in energy fluxes to higher trophic levels.