In situ observations of Scyphomedusae and Ctenophora in the coastal surface waters of the Northern Aegean Sea and the Sea of Marmara

Distribution and abundance of Scyphomedusae (Aurelia aurita, Rhizostoma pulmo) and Ctenophora (Mnemiopsis leidyi, Beroe ovata) were investigated via in situ observations (by snorkelling, boat, observation along the coastline) in summer and autumn periods between 1998 and 2005. Both scyphomedusae showed a wide distribution in the Northern Aegean and the Sea of Marmara (Turkey). A. aurita, which was dominant in the summer, decreased in fall, but R. pulmo showed a clear increase in that period. Ctenophores showed no distribution in the Northern Aegean. M. leidyi occurred abundantly in 1999 in the Sea of Marmara, displaying a sharp decrease in density in 2000 when B. ovata occurred. Both ctenophores disappeared in 2004 and 2005 in the study area, which most probably indicates a great diminution in the density of M. leidyi.