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To study the environmental impact of the assessment technologies for the development of shallow methane hydrate zones in the Sea of Japan, deep-sea amphipods (Pseudorchomene sp. and Anonyx sp.) were collected from a depth of approximately 1000 m and were tested for H 2 S toxicity. At 0.57 mg L−1 H 2 S, all specimens of Pseudorchomene sp. were dead after 96 h, whereas all individuals survived at 0.18 mg L−1. Moreover, Anonyx sp. had a survival rate of 17 % after 96 h at 0.24 mg L−1. A similar toxicity test was conducted with the coastal amphipod Merita sp., a detritivore, and all individuals died within 24 h at 0.15 mg L−1. These results suggested that compared with coastal detritivorous amphipods, deep-sea detritivorous amphipods, which also live near biomats with sediment H 2 S concentrations exceeding 10 mg L−1, showed a higher tolerance to H 2 S. • Deep-sea amphipods collected from CH 4 hydrate zones were exposed to H 2 S. • Anonyx sp. and Pseudorchomene sp. were identified based on molecular analysis. • We were able to transport and experiment on Pseudorchomene sp. • Pseudorchomene sp. not exposed to H 2 S survived for >1 year. [ABSTRACT FROM AUTHOR]

A bacterium termed 7CY, capable of decomposing cyanobacterial toxins, was isolated from surface water sample of Lake Suwa and degradation of microcystin-RR and nodularin-Har was investigated. The isolated 7CY was a gram-negative, aerobic bacillus, and a member of a genus Sphingomonas.The strain degraded microcystin-LY, -LW, and -LF completely as well as microcystin-LR within 4 days after their addition (6 μg/ml) whereas degradation of nodularin-Har did not occur at all during experiment. On the contrary, the strain was capable of degrading nodularin-Har in the presence of microcystin-RR and both toxins were completely decomposed within 6 days. The strain scarcely degraded nodularin-Har in the presence of microcystin-RR when glucose and ammonium chloride were added to the medium. The degradation of nodularin-Har did not occur in the medium from which bacterial cells had been removed after degradation of microcystin-RR. Furthermore, when microcystin-RR and nodularin-Har were added to the cytoplasm fraction of 7CY cells, microcystin-RR was rapidly degraded within 18 h, but nodularin-Har was not. The strain 7CY may require an enzyme(s) induced during the degradation of microcystin-RR in order to utilize nodularin-Har as nutrition. [Copyright &y& Elsevier]

We investigated relationships between features of benthic macrofaunal communities and geochemical parameters in and around microbial mat-covered sediments associated with a methane seepage on Sakata Knoll in the eastern Japan Sea. A depression on top of the knoll corresponds to a gas-hydrate-bearing area with seepage of methane-rich fluid, and microbial mats cover the seafloor sediments. Sediment cores were collected at three sites for this study: one within a microbial mat, a second a few meters outside of the microbial mat, and a third from a reference site outside the gas-hydrate-bearing areas. Morphological analysis showed that the site inside the microbial mat had higher macrofaunal density and biomass compared with the other sites. 18S rRNA gene analysis showed that annelids were dominant in the surface sediment inside the microbial mat with the possible occurrence of microbial anaerobic oxidation of methane (AOM), whereas in the surface sediments outside the microbial mat and at the reference site the predominant species belonged to phylum Cercozoa. Morphological analysis also showed that the surface sediment inside the microbial mat noticeably favored annelids, with dorvilleid Ophryotrocha sp. and ampharetid Neosabellides sp. identified as major constituents. Statistical analysis showed that sulfidic sediment conditions with concentrations of H 2 S up to 121 μM resulting from AOM likely resulted in the predominance of annelids with tolerance to sulfide. Both the 18S rRNA genes and macrofaunal characteristics showed that benthic biodiversity among the three sites was greatest outside the microbial mat. The site outside the microbial mat may represent geochemical transition conditions, including a lower rate of upward methane gas-flow compared with the site inside the microbial mat. The high biodiversity there might result from the presence of species specifically suited to the transition zone as well as species also found in photosynthesis-based communities of the background environment. [Display omitted] • Microbial mats overlie methane seepage sediments on Sakata Knoll in the Japan Sea. • Methane diffusion affects redox conditions and organic matter supply in the sediments. • Benthic communities dominated by annelids are related to sulfidic sediments. • The environment outside the microbial mats has higher biodiversity than inside. [ABSTRACT FROM AUTHOR]

Abstract: Chemical analysis of a marine-derived Vibrio sp. (Q-459) isolated from a depth of 10m near Okinawa prefecture Japan, yielded a new cyclic acyldepsipeptide, kailuin F (1) together with the known kailuins B (3) and E (6). The structure of 1 was elucidated based on spectroscopic methods including UV, HR-ESIMS, chemical derivatizations and 1D, 2D NMR data. Kailuin B (3) exhibited a strong antimicroalgal activity against the dinoflagellate Prorocentrum micans. [Copyright &y& Elsevier]

In deep-sea environments, which have low densities of large benthic animals, meiofauna are a useful indicator of biodiversity. However, in low-latitudes and in low-productivity areas, meiofaunal density is low, but is higher than that of megafaunal or macrofaunal density. Therefore, it is difficult to collect a sufficient number of specimens for statistical analysis. In addition, because faunal classification has been based on conventional microscopic observations, the use of meiofauna to estimate biodiversity in deep-sea environments is time-consuming. However, metabarcoding analyses focused on environmental DNA (eDNA) or RNA (eRNA) have recently been used to examine deep-sea eukaryotic diversity and communities. Here, we examined meiofaunal assemblages using microscopic, eDNA-, and eRNA-based methods at Xufu Guyot (JA06 Seamount), off the southeastern coast of Minami-Torishima Island in the North Pacific Ocean. Microscopic analysis failed to detect a significant difference in diversity or community structure between the seamount terrace and base. This was likely because of the low abundance of meiofauna, which was caused by the low surface productivity at the study area. However, eDNA/eRNA-based metabarcoding analyses revealed spatial variations in diversity and community structures within a single seamount. Therefore, metabarcoding analysis might be useful to elucidate meiofaunal assemblages in areas with low productivity and low faunal density. • Meiofaunal assemblages at JA06 Seamount were examined using the conventional and metabarcoding methods. • The conventional methods failed to detect the heterogeneity of meiofaunal assemblages. • The metabarcoding methods provided invaluable information on meiofaunal assemblages. • The metabarcoding analysis is useful to reveal meiofaunal assemblages in areas with low productivity and low faunal density. [ABSTRACT FROM AUTHOR]