FAUNAL COMMUNITY STRUCTURE OF A CHEMOAUTOTROPHIC ASSEMBLAGE ON WHALE BONES IN THE DEEP NORTHEAST PACIFIC-OCEAN

Modern and fossil chemoautotrophic communities supported by organic-ri ch whale skeletons have been reported from the bathyal-abyssal seafloo r in the eastern and western North Pacific. Based on studies with the research submersible ALVIN, we describe here general habitat character istics, and macro- and megafaunal community structure of one such comm unity, estimated to be >4 yr old, associated with an 18 m balednopteri d skeleton at 1240 m in the Santa Catalina Basin (SCB) off California, USA. The visible remains of the whale in 1988-91 consisted of partial ly buried skeletal material (primarily vertebrae and the head complex) with a plan area Of approximately 7.9 m2. White and yellow mats of su lfur-oxidizing bacteria covered many of the bone surfaces, yielding an estimated mat area of at least 4.0 m2. Bone collections indicated a t otal attached macrofaunal community of at least 12490 individuals dist ributed among greater-than-or-equal-to 43 species, with 6 species with population sizes of >1000 individuals. Megafauna associated with the skeleton consisted primarily of the vesicomyid clam Vesicomya cf. giga s, with an estimated population size of 400 to 800 individuals. The wh ale-skeleton faunal community was taxonomically distinct from that of the surrounding SCB, with >97% of its individuals belonging to species very rare or absent in background sediments. The whale-skeleton assem blage exhibited strong taxonomic and functional affinities to other de ep-sea reducing habitats (e.g. hydrothermal vents and cold seeps), mar ked by a prominence of vesicomyid clams and mytilid mussels with sulfi de-oxidizing, chemoautotrophic bacterial endosymbionts. In addition, 5 of the whale-fall species (Pyropelta corymba, P. musaica, Bathykurila guaymasensis, Idasola washingtonia and Cocculina craigsmithi) also ap pear to occur at Juan de Fuca and/or Guaymas Basin hydrothermal vents, despite geographic separation of approximately 1800 km. We conclude t hat whale falls may nurture substantial, sulfide-dependent communities at the deep-sea floor, and that some species may be dispersing to hyd rothermal vents from whale-fall habitat islands.