Organic carbon and nitrogen, sediment composition, and clay mineralogy of Deep Sea Drilling Project Site 603, western Atlantic Ocean

Sediment and interstitial water samples recovered during DSDP Leg 93 at Site 603 (lower continental rise off Cape Hatteras) were analyzed for a series of geochemical facies indicators to elucidate the nature and origin of the sedimentary material. Special emphasis was given to middle Cretaceous organic-matter-rich turbidite sequences of Aptian to Turanian age. Organic carbon content ranges from nil in pelagic claystone samples to 4.2% (total rock) in middle Cretaceous carbonaceous mudstones of turbiditic origin. The organic matter is of marine algal origin with significant contributions of terrigenous matter via turbidites. Maturation indices (vitrinite reflectance) reveal that the terrestrial humic material is reworked. Maturity of autochthonous material (i.e., primary vitrinite) falls in the range of 0.3 to 0.6% Carbohydrate, hydrocarbon, and microscopic investigations reveal moderate to high microbial degradation. Unlike deep-basin black shales of the South and North Atlantic, organic-carbon-rich members of the Hatteras Formation lack trace metal enrichment. Dissolved organic carbon (DOC) in interstitial water samples ranges from 34.4 ppm in a sandstone sample to 126.2 ppm in an organic-matter-rich carbonaceous claystone sample. One to two percent of DOC is carbohydratecarbon.

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.

(Table 1) Dissolved and particulate organic carbon, phosphorus, and nitrogen in waters of the Sea of Japan

Concentrations of dissolved and particulate organic carbon (DOC and POC, respectively), phosphorus (DP and PP, respectively) and particulate organic nitrogen (PON) were determined at Station VITYAZ6656 in the Sea of Japan in 12 sea water samples collected in June 1972 with a 200-liter sampling bottle. Mean weighted concentrations from the surface to 2000 m were: DOC - 1.58 mg/l, POC - 17.9 µg/l, DP - 13.9 µg/l, PP - 0.185 µg/l, PON - 2.7 µg/l, the ratios were DOC:DP=100:9 and POC:PON:PP=100:14:1. Relation between POC (µg/l)and the light attenuation index "e" (1/m) for the visible part of the spectrum is described by the equation POC = ca. 170e. The maximum of POC in the upper layer correlated with the maxima of phyto- and bacterioplankton and protozoa.

Organic carbon in waters, suspended matter, and upper layer bottom sediments of the Kara Sea and Obskay Guba

Along three sections in the Kara Sea and Obskaya Guba concentrations of dissolved and particulate organic carbon (DOC and POC, respectively) in waters , as well as of organic carbon in bottom sediments (Corg) in September-October 2007 were determined. DOC varied from 6.3 to 2400 µg/l, POC - from 0.84 to 12.2 mg/l. For all samples the average DOC was 200 µg/l (n = 78; sigma = 368), the average POC - 2.7 mg/l (n = 92; sigma = 2.7). Concentrations of Corg in dried samples of upper layer bottom sediments varied from 0.13 to 2.10% (aver. = 0.9%; n = 21; sigma = 0.49%). It is shown that distribution of different forms of organic matter (OM) is an indicator of supply and scattering of particulate matter in the Kara Sea and that DOC and POC of the Kara Sea are formed under impact of runoff of the Ob and Yenisei Rivers. It is found that distribution of OM in bottom sediments is closely related to their grain size composition and to the structure of currents in the area. Variations in Corg concentration in bottom sediment cores from the zone of riverine and sea water mixing represent variability of OM burial.