Dissolved and particulate organic carbon in the Sea of Okhotsk

Data on distribution of dissolved and particulate organic matter obtained during Cruises 21 and 24 of R/V Akademik A. Nesmeyanov in June-August 1992 and 1993 are presented. In general a remarkable heterogeneity in distributions of both dissolved and particulate organic carbon is revealed. Concentrations of dissolved organic carbon vary from 98 to 700 µmol/l and those of particulate organic carbon vary from 3 to 50 µmol/l. Maximum concentrations are commonly observed in the shelf region while minimum concentrations - in the central basin. Run-off of the Amur River raises dissolved matter concentration in the Sakhalin Bay, while oil exploitation at the Sakhalin shelf maximizes particulate organic carbon concentration and minimizes dissolved one. Concentrations of dissolved and particulate organic carbon in the surface microlayer were estimated for the first time and are shown to be 1.5-2.0 times higher than in surface waters.

Stable isotope (carbonates), organic carbon, calcium carbonate and occurrence of coccoliths at DSDP Hole 71-511

Thin but discrete pelagic limestone beds intercalated among the black mudstones near the top of the extensive Mesozoic black shale sequence of the Falkland Plateau are reminiscent of similar occurrences in the central and North Atlantic and may be cyclic in nature. They have been studied via carbonate, organic carbon, stable isotope, nannofloral, and ultrastructural analysis in an attempt to determine their mode of origin. Nannofossil diversity and preservation suggest that selective dissolution or diagenesis did not produce the interbedded coccolith-rich and coccolith-poor layers, nor did blooms of opportunistic species play a role. Stable isotope measurements of carbonate do not adequately constrain the origin of the cyclicity; however, the d13C data suggest that the more nannofossil-rich intervals may be due to higher nutrient supply and overturn of deeper waters at the site rather than influxes of well-oxygenated waters into an otherwise anoxic environment. Such an explanation is in accord with the nannofloral evidence