Nishihara, Japan
Nishihara, Japan

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Arakaki T.,Biology and Marine Science | Anastasio C.,University of California at Davis | Kuroki Y.,University of Ryukyus | Nakajima H.,University of Ryukyus | And 8 more authors.
Environmental Science and Technology | Year: 2013

Hydroxyl radical (OH) is an important oxidant in atmospheric aqueous phases such as cloud and fog drops and water-containing aerosol particles. We find that numerical models nearly always overestimate aqueous hydroxyl radical concentrations because they overpredict its rate of formation and, more significantly, underpredict its sinks. To address this latter point, we examined OH sinks in atmospheric drops and aqueous particles using both new samples and an analysis of published data. Although the molecular composition of organic carbon, the dominant sink of OH, is extremely complex and poorly constrained, this sink behaves very similarly in different atmospheric waters and even in surface waters. Thus, the sink for aqueous OH can be estimated as the concentration of dissolved organic carbon multiplied by a general scavenging rate constant [kC,OH = (3.8 ± 1.9) × 108 L (mol C)-1 s-1], a simple process that should significantly improve estimates of OH concentrations in atmospheric drops and aqueous particles. © 2013 American Chemical Society.

Reimer J.D.,University of Ryukyus | Reimer J.D.,Japan Agency for Marine - Earth Science and Technology | Sinniger F.,Biology and Marine science | Sinniger F.,Bangor University
Cahiers de Biologie Marine | Year: 2010

Until recently, very little was known about zoanthids (Cnidaria: Hexacorallia) from deep-sea environments, with all known specimens assigned to the family Epizoanthidae. However, in June 2005 a small number of unusual samples of a zoanthid-like species were sampled during deep-sea submersible dives (Shinkai 6500 dive # 884) at a methane cold seep at 3259 m in the Nankai Trench off Muroto, Japan (32O34.945'N-134O41.545'E). Specimens were highly divergent in ecology, morphology and molecular phylogeny from all known families of zoanthids, and were thus classified as the new species Abyssoanthus nankaiensis Reimer & Fujiwara, 2007 belonging to the new family Abyssoanthidae. A. nankaiensis is distinguished by its unitary polyps, presence at methane cold seeps at extreme depths, and divergent phylogenetic status from other zoanthids. Unfortunately, due to difficulties in histology and the very small number of specimens, many questions remain on the ecology and morphology of A. nankaiensis. From images taken during Shinkai 6500 dive # 959 it was hypothesized that there were other potential Abyssoanthidae populations at a non-methane seep site at the Japan Trench (39°06.50'N-143°53.4'E). In October 2007, JAMSTEC cruise YK07-15 and the Shinkai 6500 dove to a depth of 5347-5360 m (dives # 1038 & 1041) at this site to confirm the presence of zoanthids. Our molecular (mitochondrial 16S ribosomal DNA) and morphological (dimensions, cnidome) findings show a large population of a new species, Abyssoanthus convallis, living on mudstone in an "ecological hotspot" characterized by large amounts of marine snowfall. Specimen polyps in situ were approximately 15-25 mm in height, 5-15 mm in diametre, and had 20-30 tentacles. This species of zoanthids represents the deepest recorded zoanthid population, and further investigations at other hadal sites will increase our knowledge of these understudied benthic cnidarians.

Agostini S.,University of Shizuoka | Suzuki Y.,University of Shizuoka | Higuchi T.,University of Shizuoka | Casareto B.E.,University of Shizuoka | And 3 more authors.
Coral Reefs | Year: 2012

All corals have a common structure: two tissue layers enclose a lumen, which forms the gastric cavity. Few studies have described the processes occurring inside the gastric cavity and its chemical and biological characteristics. Here, we show that the coral gastric cavity has distinct chemical characteristics with respect to dissolved O 2, pH, alkalinity, and nutrients (vitamin B 12, nitrate, nitrite, ammonium, and phosphate) and also harbors a distinct bacterial community. From these results, the gastric cavity can be described as a semi-closed sub-environment within the coral. Dissolved O 2 shows very low constant concentrations in the deepest parts of the cavity, creating a compartmentalized, anoxic environment. The pH is lower in the cavity than in the surrounding water and, like alkalinity, shows day/night variations different from those of the surrounding water. Nutrient concentrations in the cavity are greater than the concentrations found in reef waters, especially for phosphate and vitamin B 12. The source of these nutrients may be internal production by symbiotic bacteria and/or the remineralization of organic matter ingested or produced by the corals. The importance of the bacteria inhabiting the gastric cavity is supported by the finding of a high bacterial abundance and a specific bacterial community with affiliation to bacteria found in other corals and in the guts of other organisms. The findings presented here open a new area of research that may help us to understand the processes that maintain coral health. © 2011 Springer-Verlag.

Two new species, Dracoderes snufkini sp. nov. and Dracoderes toyoshioae sp. nov., are described from Okinawa, southern Japan. Diagnostic characters of D. snufkini include: lateroventral tubules on segments 2 and 5; a thick, plump middorsal spine on segments 2 and 9; thick plump paradorsal spines on segments 3-8, alternately laterally displaced; and a ventral primary pectinate fringe on segment 1, with long, wide conspicuous tips. Diagnostic characters of Dracoderes toyoshioae include: a middorsal subcuticular structure on segment 1; paradorsal subcuticular structures on segments 2-9, alternately laterally displaced; paradorsal acicular spines arising from subcuticular structures, at least on segment 5; ventrolateral acicular spines on segment 1; lateral accessory tubules on segment 2; lateral accessory subcuticular structures on segments 2-7; lateroventral tubules on segment 5; and lateroventral subcuticular structures on segments 2-10. Molecular phylogenetic analyses based on 18S rRNA, 28S rRNA and mitochondrial COI sequences indicate that D. abei and D. nidhug are more closely related to one another than either is to D. snufkini or D. toyoshioae. Copyright © 2015 Magnolia Press.

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