Dynamics and trofic ecology of Noctiluca scintillans (Macartney) Kofoid & Swezy, 1921 in the Southeastern Black Sea

Dynamics and food preference of Noctiluca scintillans and its relation with environmental parameters were investigated between May 2015 and April 2016 in river mouth, coastal and open waters of Southeastern Black Sea. In the study area, well-mixed waters in winter and thermally stratified waters in summer were observed. Lower surface salinity was observed from spring to summer due to river discharges. During the study, cell diameter and volume of Noctiluca scintillans varied between 410-663 µm and 0,05-0,15 mm-3, respectively. Noctiluca scintillans abundance and biomass ranged between 0-5567 cells.m-3 and 0-33.6 mg C.m-3, respectively. In the study area, the highest abundance was recorded during May. Noctiluca scintillans abundance tended to decrease from river mouth to open waters. Contribution of Noctiluca scintillans to mesozooplankton ranged between 0-94 %. To assess feeding ecology, 6400 cells of Noctiluca scintillans were examined and nine different type of food group (diatom, dinoflagellate, microzooplankton, holoplankton and meroplankton larvae, micrometazoa egg, pine polen, fecal pelet and unidentified food) were found in food vacuole. During study, maximum four types of prey were found at food vacuole of Noctiluca scintillans. Noctiluca scintillans represented selective feeding habit. Micrometazoa eggs were the most common and preferred food, followed by fecal pelets and unidentified food. The results of this study show Noctiluca scintillans is an important component of mesozooplankton in the Southeastern Black Sea. Our results suggest that Noctiluca scintillans, might play an important role on structuring zooplankton communities and plantivorous fish populations by selective feeding in particular on copepod eggs.