Extant silicoflagellates from the Northeast Aegean (eastern Mediterranean Sea): Morphologies and double skeletons

Silicoflagellate abundance, vertical distribution and morphology were studied during spring (March 2014) at three sampling stations located in the Northeast Aegean Sea adjacent to the Dardanelles Strait and characterized by a variable influx of cold, low-salinity Black Sea water. The silicoflagellate assemblage was dominated by Dictyocha stapedia and Stephanocha speculum with minor contribution of D. aculeata and Octactis pulchra. While specimens of D. stapedia were represented by the typical morphologies described in other areas of the Mediterranean Sea, populations of S. speculum displayed peculiar characters: they were large, predominantly 7-sided, with a small apical ring as well as apical ring spines, concave basal ring sides and non-rotated apical structure. Some of these features have been described for S. speculum at high latitudes, but the combined characters make these specimens slightly different from the high latitude populations. Similar morphologies have been observed in the western Black Sea, thus we can infer that the peculiar specimens detected in the Northeast Aegean are associated with the influx of Black Sea water masses.