Mesozooplankton stable isotope composition in Cyprus coastal waters and comparison with the Aegean Sea (eastern Mediterranean)

Here we use bulk and amino acid-specific stable nitrogen (N) isotope analysis (AA-CSIA) to evaluate seasonal and regional change in mesozooplanlcton dynamics for the first time in coastal waters of the eastern Mediterranean. Cyprus mesozooplankton delta N-15 values were significantly higher in late winter (23 parts per thousand) than in summer (1.2 parts per thousand), and in all cases were less than the delta N-15 values of mesozooplankton in the northeast Aegean Sea (NEA; 3.4 parts per thousand). AA-CSIA indicates that these differences can primarily be attributed to seasonal and regional change in mesozooplankton community trophic structure, with overall trophic position increasing by 0.2-0.3 in winter as compared to summer around Cyprus, and trophic position higher in the NEA than in Cyprus by 0.3-0.6. Such differences are most likely related to the larger contribution of carnivorous mesozooplankton observed in winter around Cyprus and in the NEA. Overall, our findings indicate change in bulk mesozooplankton delta N-15 value in the eastern Mediterranean is primarily driven by change in community trophic position, rather than variability in delta N-15 value at the base of the food web. (C) 2014 Elsevier Ltd. All rights reserved.