Galaxea, Journal of Coral Reef Studies Vol. 19(2017) No. 1

Coral “holobiont” is defined as a complex as-semblage which is comprised of the coral animal and its associated microorganisms. These organisms (including bacteria, archaea, cyanobacteria, fungi and also virus) inhabit coral tissues, coral skeleton, and the coral surface forming the so-called surface mucus layer (SML). The SML bears a diverse assemblage of antagonistic bacteria which suppress overgrowth of other microorganisms and maintain the healthy status of coral holobiont. On the basis of this background, we accomplished the isolation of antagonistic bacteria associated with Montipora digitata colonies sampled at Sesoko Island, Okinawa, Japan. As a result, 13 strains of antagonistic bacteria were isolated and identified by the analysis of partial 16S rDNA sequences. The bacteria were identified to belong to either the genus Pseudoalteromonas, Vibrio, or Staphylococcus. We attempted isolation of antifungal compounds from newly isolated Pseudoalteromonas sp. S10. By analysis of NMR and ESI-MS spectral data, the antifungal com-pounds were identified as known macrolactams alter-amides A and B.

Recent developments in deep-sea surveys have revealed the widespread distribution of cold-water corals over the deep-sea floor of the world ocean. There are no reports, however, concerning the taxonomic composition of cold-water corals and other benthic megafauna in the southern Emperor Seamounts area of the North Pacific Ocean. We analyzed benthic samples collected from a research vessel during scientific surveys and by scientific observers onboard commercial fishing vessels to examine the faunal composition of cold-water corals and other megabenthos in the southern Emperor Seamounts area. Seventy-eight genera of cold-water corals were identified. Gorgonians (Alcyonacea with solid axis) occurred at high frequencies with wide vertical distribution ranges, and appeared to be the major components of habitat-forming cold-water corals in the area. Scleractinia occurred at frequencies similar to those of gorgonians, but over lim-ited depth ranges. Among other benthic megafauna, Crus-tacea and Echinodermata occurred at high frequencies. The results demonstrates that the regional characteristics of deep-sea benthic megafauna in the southern Emperor Seamounts area is more similar to that near the Hawaiian Islands than those reported from Aleutian, other Alaskan, Californian and Japanese waters.