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We examined the reproductive biology of three dominant pseudoceanic myctophids, Diaphus garmani , D. chrysorhynchus , and D. watasei , on the slope region of the East China Sea. Overall, females were more abundant in D. garmani and D. chrysorhynchus , while males were more abundant in D. watasei . The gonadosomatic index (GSI) at 50% sexual maturity of females of D. garmani , D. chrysorhynchus , and D. watasei was 3.65, 3.92, and 6.27, respectively. Based on these criteria, females of each species can mature at sizes larger than 42, 71, and 120 mm standard length (SL), respectively. In all three species, GSI of females showed high values during summer, i.e. the primary spawning season, and occurrence of females with hydrated ovaries was restricted to the daytime (0600–1530 h) in the mesopelagic layer of 270–450 m depth. Oocytes at various sizes were found in mature ovaries, indicating that they are multiple spawners. Spawning frequencies were estimated to be approximately 3–9 days. Mean egg size at hydration and batch fecundity was respectively smallest and lowest in D. garmani (0.60 mm and 612–2200 eggs) and largest and highest in D. watasei (0.65 mm and 10,356–44,879 eggs). Batch fecundity increased linearly with SL in all species, with a steeper slope in D. watasei. Diaphus garmani is characterized by early maturation at a smaller size, while D. watasei channels a larger part of the energy budget into somatic growth during the juvenile and later immature stages (<120 mm SL) than the other two species and subsequently reproduces at a larger size as mature adults. [ABSTRACT FROM AUTHOR]

The East China Sea is an important marginal sea of the Western Pacific Ocean, from which natural gas hydrate sample has not been acquired so far. Recently, copious carbonate chimneys have been discovered in turbidite deposits in the olistostrome zone located on the west slope of the northern section of Okinawa Trough. Here, the petrology, geochemistry and chronology of an iron-rich carbonate chimney were characterized, confirming a close relationship between its formation and the dissociation of natural gas hydrate beneath the chimney in OT. A distinctive relationship has been observed between goethite and total carbonate contents along with a negative correlation between Fe and Ca contents. Conversely, abundant Fe accumulated on carbonate substrate by mineralized microorganisms. The δ 13 C values of the chimney wall were from −27.56 to −43.66‰ (average: −37.18‰, V-PDB), implying anaerobic oxidation of methane (AOM) as a predominant controlling factor on carbonate precipitation. As no pyrite and organic residues were identified in the iron-rich chimney, it was assumed that AOM was coupled to the iron reduction reaction at least to some extent during the chimney growth owing to the local deficiency of sulfate supply. The δ 56 Fe values of bulk chimney wall (ranging from −0.316‰ to −0.023‰, average −0.134‰) suggest mass and isotope exchanges between the chimney and ambient environment during its growth history, whereas the enrichment of δ 18 O of the carbonate implies these carbonate sourcing from hydrate dissociation underlying our sampling site. This assumption has been supported by a distinct bottom simulation reflector (BSR) and a well-developed fault system beneath the sampling site. This is the first report of cold seepage inside the OT and the identified iron-dependent AOM has shed a new light to the Carbon cycle related to the marine methane oxidation, particularly before the Great Oxidation Event ~2.45 Ga ago. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the spatial and temporal surface variability along the entire Kuroshio Current in the East China Sea (ECS) using 16-year (1993–2008) surface geostrophic currents derived from satellite altimetry data. Our analysis is based on stream coordinate and physically sensible definitions of the axis, width, along- and cross-stream transports. Mainly flowing along the 200m isobath, the Kuroshio''s width narrows from ∼218km in the winter towards ∼207km in the summer while the surface transport increases from a minimum of 6.8×104 m2/s in the autumn to a maximum of 7.4×104 m2/s in the summer. The width, surface transport, and the magnitude of the along-stream velocity of the Kuroshio are positively correlated along its track and have relatively large values in the central ECS. The shoreward intrusion that departs from the mainstream chiefly occurs near the southwest of Kyushu where an estimated transport of 1.8Sv of the Kuroshio veers towards the Tsushima Strait throughout the year. The surface shoreward intrusion in other parts of the Kuroshio is generally weak and most of the transport that deviates shoreward from the core (around the 200m isobath) of the Kuroshio recirculates within the stream. The net surface transport induced by Ekman process along the stream contributes to the surface shoreward intrusion, and the intrusion in the entire vertical water column is, nevertheless, controlled by the local geostrophic current. The spatial structure of the intrusion is mostly governed by the response of stream to shelf topography between the 200m isobath and the shore-side boundary. The transport across the shore-side boundary of the Kuroshio is considerably different from the transport across the 200m isobath, and the former better reflects the water exchange between the stream and the ECS shelf. [Copyright &y& Elsevier]