A multispecific accumulation of gelatinous organisms in the central Aegean Sea as a case of biological evidence for unnoticed offshore events

Abstract

An exceptionally high density of gelatinous organisms was observed in May 2015, off the coasts of Doganbey, central Aegean Sea. Eight gelatinous species were found in the accumulation, with salps being the main component. The hydromedusae Solmaris corona and Aequorea forskalea, the siphonophore Nanomia bijuga and the ctenophore Leucothea sp. are recorded for the first time from the Aegean Sea. The hydromedusa S. corona, the siphonophores Hippopodius hippopus and N. bijuga, the salp Salpa maxima and the ctenophore Leucothea sp. are first records for the Turkish coasts. We suggest that the various life histories and different ecological traits of the gelatinous components in the accumulation are indicators of an apparent bloom, i.e., the organisms bloomed/increased their abundances in response to different processes and were aggregated only subsequently at the coast, due to strong southwesterly winds and north-eastward currents originating a few days prior to our observations. The offshore area facing Doganbey is characterized by a large gyre coupled with one of the most vigorous upwelling zones in the Mediterranean Sea, therefore creating favourable conditions for the aggregation of salps and the presence of siphonophores.