The peculiar planktonic hydrozoan fauna of San Matías gulf and adjacent areas; Patagonia, Argentina.

GUERRERO E.; GILI J. M.; RODRIGUEZ C.; ARAUJO E.; GENZANO G. N.; MIANZAN H.; CALBET A.; GONZALEZ R.

Lecce

Workshop; Seventh International Workshop of the Hydrozoan Society; 2010

Hydrozoan society

THE PECULIAR PLANKTONIC HYDROZOAN FAUNA OF SAN MATÍAS GULF AND ADJACENT AREAS; PATAGONIA, ARGENTINA Guerrero, E1, Gili, J-M1, Rodriguez, C2, De Araujo, E M2, Genzano, G2, Mianzan, H W3, Calbet, A1 & González, R A4 1Institut de Ciences del Mar, CSIC, Barcelona, Spain (eguerrero@icm.csic.es) 2Estación Costera J. J. Nágera, Universidad Nacional de Mar del Plata, Argentina 3Instituto Nacional de Investigación y Desarrollo Pesquero, Mar del Plata, Argentina 4Instituto de Biología Marina y Pesquera “Almirante Storni”, San Antonio Oeste, Argentina Specific richness, abundance and distribution of planktonic cnidarians from San Matías Gulf (SMG; 40° 50´ - 42° 15´ S and 63° 05´ - 65° 10´ W) and adjacent areas (San Jose Gulf and Argentine continental shelf contiguous to SMG) were studied over a seasonally cycle. SMG is a semi-enclosed area with an important seasonally oceanographic influence from adjacent continental shelf water mass –at least in its southern area. Four oceanographic cruises and 93 sampling stations were conducted between 2007-2008. A total of 21 species of hydromedusae and one siphonophore were identified. All hydromedusae correspond to Antho- and Leptomedusae subclasses, meroplanktonic species dominated by its benthic stage (polyp phase) in their life cycle. Unexpectedly, maximum total hydromedusae abundance occurred during autumn-winter season, mainly due to a real bloom caused by Obelia spp. However, species richness was higher during spring. The unique siphonophore found for the area, the physonect Pyrostephos vanhoeffeni, described as endemic to Antarctic and Subantarctic waters, dominated the holoplanktonic niche in SMG. The general distribution of planktonic cnidarians in SMG shows a very singular pattern different from others similar geographic areas, for instance in relation to the lack of Narco- and Trachymedusae and calycophoran siphonophores. This peculiar phenomenon is discussed based on hydrographical and biological features of the system.