Molecular hydrogen and carbon monoxide in seawater in an area adjacent to Kuroshio and Honshu Island in Japan

Marine H2 and CO cycles in the sea adjacent to Honshu Island in Japan were investigated using vertical and diurnal seawater sampling. The vertical profiles of the H2 concentration differed among three stations that were located near the Kuroshio Current, off Suruga Bay, and in the center of Sagami Bay. Surface H2 enrichment was found near the Kuroshio Current, whereas subsurface H2 maxima within the pycnocline appeared at the Kuroshio and Suruga Bay stations. Biological N2 fixation likely accounts for the surface and subsurface H2 enrichment while the fermentative H2 production remains as the other possible process. In addition, twenty-four-hour observation at the Sagami Bay station revealed nearly constant H2 levels through depth and time, whereas a noon-high surface-high pattern was observed in the CO concentrations.