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The number of records of the genus Prionospio Malmgren, 1867, from the deep sea (>2000 m) are relatively few and do not reflect the actual occurrence of species nor their potential ecological importance. In this paper we describe five new species of this genus (Prionospio amarsupiata sp. nov., P. vallensis sp. nov., P. branchilucida sp. nov., P. hermesia sp. nov. and P. kaplani sp. nov.) all of which are abundant members of the deep-sea community. We also describe two new species of the genus Aurospio Maciolek, 1981 (Aurospio abranchiata sp. nov. and A. tribranchiata sp. nov.) again common elements of the abyssal fauna. Two of the new species have characters which question the generic distinctiveness of Prionospio and Aurospio. The problems in differentiating these two genera are discussed.

Whale falls cause massive organic and sulfide enrichment of underlying sediments, yielding energy-rich conditions in oligotrophic deep-sea ecosystems. While the fauna colonizing whale skeletons has received substantial study, sediment macrofaunal community response to the geochemical impacts of deep-sea whale falls remains poorly evaluated. We present a 7 yr case study of geochemical impacts, macrofaunal community succession, and chemoautotrophic community persistence in sediments around a 30 t gray-whale carcass implanted at 1675 m in the well-oxygenated Santa Cruz Basin on the California margin. The whale fall yielded intense, patchy organic-carbon enrichment (>15% organic carbon) and pore-water sulfide enhancement (> 5 mM) in nearby sediments for 6 to 7 yr, supporting a dense assemblage of enrichment opportunists and chemosymbiotic vesicomyid clams. Faunal succession in the whale-fall sediments resembled the scavenger-opportunist-sulfophile sequence previously described for epifaunal communities on sunken whale skeletons. The intense response of enrichment opportunists functionally resembles responses to organic loading in shallow-water ecosystems, such as at sewer outfalls and fish farms. Of 100 macrofaunal species in the whale-fall sediments, 10 abundant species were unique to whale falls; 6 species were shared with cold seeps, 5 with hydrothermal vents, and 12 with nearby kelp and wood falls. Thus, whale-fall sediments may provide dispersal stepping stones for some generalized reducing-habitat species but also support distinct macrofaunal assemblages and contribute significantly to beta diversity in deep-sea ecosystems.

Whale bones and wood on the deep-sea floor provide resource pulses that support characteristic faunal assemblages in an otherwise food-poor environment. To isolate the role of bathymetric and geographical drivers of organic-fall diversity and community structure, the study of organic-rich substrates of similar sizes, qualities, and seafloor durations is necessary. We used a comparative experimental approach to examine the roles of depth, location, and substrate type in structuring organic-fall faunal assemblages. Four free-vehicle landers containing replicate wood, whale-bone, and inorganic hard (control) substrates were deployed for 15 mo at depths of ~1600 and ~2800 m, spaced at ~400 km along the Washington-Oregon (USA) margin. The landers collected a total of ~84890 macrofaunal individuals of 144 species. Wood, bone, and control substrates supported assemblages with different community structures on all landers. Community composition was significantly different between depths and between locations at similar depths, indicating variability on regional and bathymetric scales. Wood blocks at ~1600 m were heavily degraded by wood-boring xylophagaid bivalves. Xylophagaid colonisation was lower in deeper wood blocks, which we hypothesise results partly from lower propagule supply as wood falls decrease in abundance with distance from terrestrial sources of wood. Bone-eating Osedax colonised whale bones, but bone degradation was low compared to some NE Pacific whale falls of similar duration; nonetheless, bones exhibited reducing conditions and supported sulphophilic species. Our study demonstrates quantitatively that co-located wood falls and whale bones support highly distinct, species-rich assemblages and thus promote biodiversity on the deep-sea floor.