Relationship between environmental factors and zooplankton diversity in the Gulf of Bandirma (the Sea of Marmara)

Abstract

Zooplankton community and its relationship to environmental variables were investigated seasonally between autumn 2006 and summer 2008 in the Gulf of Bandirma (the Sea of Marmara). In the Gulf, we identified nine Copepoda, three Cladocera, one Hydrozoa, one Cydippida, Appendicularia, Bivalvia, Chaetognatha, Cirripedia, Decapoda, Echinodermata, Gastropoda, Polychaeta, Pisces larvae, and Pisces eggs at three sampling stations. Shannon-Weaver diversity index and Pielou's evenness value ranged between 0.00-2.72 and 0.00-1.00, respectively. The first two components of the redundancy analysis (RDA) explained 81.9% of the variance as the main factors (generally the longest arrows) affecting the spatial and temporal distributions of zooplankton in the Gulf of Bandirma, with dissolved oxygen (DO), nitrite+nitrate (NO3 + NO2-N) and phosphate (PO4-P). Liriope tetraphylla, Oithona nana, Paracalanus parvus, Penilia avirostris, Appendicularia and veliger larvae (Gastropoda) were positively related to DO and salinity, and negatively correlated with temperature, chlorophyll-a (Chl-a), Trophic State Index (Trix), PO4-P, and NO3 + NO2-N. According to Spearman's rank correlation analysis, there was a strong positive correlation between the number of zooplankton individuals and temperature, and the number of zooplankton individuals negatively correlated with salinity and Chl-a. In order to determine similarities among seasons in the samples, the Bray-Curtis similarity index was calculated using species diversity and abundance values, while Euclidean distances were calculated using ecological parameters. Overall, the diversity of zooplankton in the Gulf of Bandirma was higher in the first sampling year and decreased due to the effect of mucilage in the second sampling year.