Age distribution of Antarctic Bottom Water off Cape Darnley, East Antarctica, estimated using chlorofluorocarbon and sulfur hexafluoride.

Chlorofluorocarbon (CFC) and sulfur hexafluoride (SF) were used to investigate the timescale of Antarctic Bottom Water (AABW) that spreads off Cape Darnley (CD) in East Antarctica. The age of the AABW was estimated based on the observed SF/CFC-12 ratio while taking into account tracer dilution by Lower Circumpolar Deep Water. Along the western canyons off CD and the ~ 3000 to 3500 m isobaths, the bottom water age was < 5 years, reflecting the spread of newly formed CD Bottom Water.

Identifying the origin of nitrous oxide dissolved in deep ocean by concentration and isotopocule analyses.

Nitrous oxide (NO) contributes to global warming and stratospheric ozone depletion. Although its major sources are regarded as bacterial or archaeal nitrification and denitrification in soil and water, the origins of ubiquitous marine NO maximum at depths of 100-800 m and NO dissolved in deeper seawater have not been identified. We examined NO production processes in the middle and deep sea by analyzing vertical profiles of NO concentration and isotopocule ratios, abundance ratios of molecules substituted with rare stable isotopes N or O to common molecules NNO, in the Atlantic, Pacific, Indian, and Southern oceans.

Assessment of coastal turbidity improvement potential by terrigenous sediment load reduction and its implications on seagrass inhabitable area in Banate Bay, central Philippines.

This paper demonstrates the effects of terrigenous sediment load reduction by watershed managements on coastal turbidity in Banate Bay, Iloilo located in central Philippines, using field observations and numerical simulations. Measurements of the total suspended solid and particulate organic carbon indicated that the bulk component of the coastal turbidity comprised terrigenous mineral particles rather than phytoplankton at the rise of the river after heavy rain. The suspended sediment concentration and underwater light intensity were simulated by an atmosphere-watershed-coastal ocean model to investigate the contribution of the terrigenous sediment load to the coastal turbidity in rainy season.

17-year change in species composition of mixed seagrass beds around Santiago Island, Bolinao, the northwestern Philippines.

Effects of fish culture can alter the adjacent ecosystems. This study compared seagrass species compositions in 2012 with those in 1995, when fish culture was less intensive compared to 2012 in the region. Observations were conducted at the same four sites around Santiago Island, Bolinao: (1) Silaqui Island, (2) Binaballian Loob, (3) Pislatan and (4) Santa Barbara, and by using the same methods as those of Bach et al.

Surface water mixing estimated from 228Ra and 226Ra in the northwestern North Pacific.

We investigated the horizontal distributions of (228)Ra and (226)Ra in surface waters of the northwestern North Pacific Ocean and Okhotsk Sea. Ratios of (228)Ra/(226)Ra were relatively large in the Tsugaru Current (0.6-0.