The evaluation of seasonal fatty acid composition and food sources of Pileurobrachia pileus (Ctenophora) in terms of trophic marker fatty acids in the Southeastern Black Sea

Abstract

Seasonal changes of the lipid and fatty acid composition of Pleurobrachia pileus investigated monthly from March 2012 to February 2013. Average total lipid content was determined as percentage (%) and per individual (mg ind-1). It was highest in February (1.48 %; 3.55 mg ind-1). However, it was proportionally the lowest in April (0.40 %), and per individual in August (0.33 mg ind-1). Major fatty acids of P. pileus were identified as 16:0, 14:0, 11:1 n-9c, 20:5 n-3, and 22:6 n-3. P. pileus had on average 27.27 % ∑SFA, 25.04 % ∑MUFA and 47.63 % ∑PUFA content. EPA and DHA were the major fatty acids from PUFA. Seasonal changes of DHA were more obvious than EPA (p<0.05). Herbivore calanoid zooplankton trophic markers; 20:1 n-9 and DHA/EPA and herbivory trophic markers; EPA and DHA content were high in P. pileus fatty acids. It showed that herbivory fatty acids were taken by feeding from herbivory zooplankton and phytoplankton. Diet was an important factor in seasonal fatty acid changes of P. pileus. In addition, we revealed that P. pileus has a rich lipid content and fatty acid composition and plays an important role in the Southeastern Black Sea ecosystem functionalities between herbivory and carnivory species.