Deep-water Bryozoa from the Kuril Basin, Sea of Okhotsk

Benthic samples collected at six stations in the Kuril Basin, Sea of Okhotsk, at depths of 3301 to 3366 m, and at two northwestern Pacific stations in Bussol Strait and on the western slope of the Kuril-Kamchatka Trench, at depths 2267 and 3374 m, yielded three cyclostome, two ctenostome, and two cheilostome bryozoan species. Among these, Oncousoecia viskovae sp. nov. is the deepest record for a species in this genus. Triticella maiorovae sp. nov., a symbiont on a sipunculid worm, is the second species of the genus discovered in the northwestern Pacific. Our study yielded the deepest records for Bicrisia abyssicola and Buchneria teres, and the first records for Triticella minim and B. teres from the Sea of Okhotsk. The proportion of cheilostomes in the samples was much lower than expected from previous studies, although the sample size and total diversity were also low. Dead colonies of four cheilostome species, Einhornia arctica, Porella alba, Cryptosula zavjalovensis and Cheilopora praelucida, were found encrusting pebbles at two abyssal sites; we interpret these as allochthonic elements due to ice transport of pebbles from shallow waters to the Kuril Basin. Stenobathic and eurybathic species common to both the Kuril Basin and northwestern Pacific indicate connectivity between deep water faunas in these adjacent regions.