MEGAFAUNAL DIVERSITY ASSOCIATED WITH DEEP-SEA NODULE-BEARING HABITATS IN THE EASTERN PART OF THE CLARION-CLIPPERTON ZONE, NE PACIFIC.

The abundance, composition and spatial distribution of megafauna were assessed quantitatively from seafloor photographic transects carried out in July 2009 by the Interoceanmetal Joint Organization (IOM). Studied area is located in the eastern part of Clarion-Clipperton Zone, NE Pacific (10°05'-10°55'N and 119°25'-120°08'W) at depth varying from 4200 to 4600 m. Analysis of over 11000 bottom photographs revealed 8675 epibenthic animals, entering into 32 taxonomic groups. The most abundant megafaunal taxa were the sponges, sea urchins, ophiuroids, actinians and holothurians that counted about 90% from a total number of animals identified on photographs. The highest density, up to 222 ind/ha was recognized for the glass sponges (Hexactinellida) belonging to group of sessile suspension feeders; thus the mean densities of suspension and deposit trophic groups were approximately equal to 48%, and the carnivorous compound only 4% from all identified animals. The spatial distribution of megafaunal groups appears to vary with the nodule coverage, thus the polymetallic nodules clearly provide a habitat for fixed megafaunal assemblage like sponges, whereas without nodules the deposit feeders like holothurians dominated. The data review was carried out in support of the IOM as a contractor with the International Seabed Authority to provide adequate environmental baseline information necessary to assess the potential environmental impact before commercial exploitation of polymetallic nodule deposits. [ABSTRACT FROM AUTHOR]