Mass of particulate carbon and nitrogen in suspended matter as a function of volume filtered in several oceanic areas

We address two issues in the determination of particulate carbon and nitrogen in suspended matter of aquatic environments. One is the adsorption of dissolved organic matter on filters, leading to overestimate particulate matter. The second is the material loss during filtration due to fragile algal cells breaking up. Examples from both laboratory cultures and natural samples are presented. We recommend using stacked filters in order to estimate thefirst and filtering different volumes of water in order to evaluate the second.

(Table 1) Composition of lipids in particulate matter and bottom sediments of the Baltic Sea

Lipid contents in the upper layer of bottom sediments in the Baltic Sea range from 0.37 to 2.66 mg/g (1.2-25.8% Corg). It is shown that the main factors determining composition of lipids in bottom precipitates are relative roles of different sources of lipids in sediments and conditions of sediment accumulation. Runoff of the Daugava River into the Gulf of Riga contributes simple low-polarity lipids. Sterols and certain bound fatty acids originate in living organic matter. Polar lipids are formed by inheritance of complex phospholipids and glycolipids from plankton and/or by formation of polycondensates.

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.

Distribution of particulate matter and particulate organic carbon in waters of the Caspian Sea

Data on concentrations and distribution of particulate matter in the Caspian Sea obtained during surveys in 1981-1983 with use of modified filtering units have shown that over the major part of the sea concentration of particulate matter does dot exceed 1-2 mg/l. Only in the northern Caspian and in coastal regions concentrations correspond to values measured earlier. Total amount of particulate matter in the Caspian Sea is about of 90 million ton, 19.6% in the Northern Caspian, 28.1% in the Middle Caspian, and 52.3% in the Southern Caspian. Contents of carbon in particulate matter of the Central Caspian reach 30-40%, and over a significant part of the sea - 20%. A correlation has been found between areas of increased carbon contents in particulate matter and in bottom sediments. An important role of biofiltration in enrichment of particulates in organic matter has been noted. From data on carbon contents and an estimate of particulate matter input biogenic portion in particulate matter exceeds 50% for the whole sea.

Finely dispersed fraction of particulate organic matter and primary production in sea water of the Equatorial East Pacific

Qualitative and quantitative evaluation of the finely dispersed fraction of particulate organic matter in sea water is given. It is demonstrated that in the euphotic zone of high productivity waters this fraction constitutes 86%, in waters with low productivity 61%, and in deep waters (>200 m) 53% of the organic carbon in particulate matter. Formation of the finely dispersed fraction and its role in distribution of energy in the detrital food chain of the ecosystem are discussed.

Lipids in ocean particulate matter and bottom sediments

Lipid contents both in particulate matter and bottom sediments decreases with passage from the shelf toward the open ocean. Lipid concentration in particulate matter collected by a separator (Ls) decreases by a factor of 7 (from 7.05 to 0.95 % of dry matter), while in particulate matter collected on filters (Lf) it decreases by a factor of 13 (from 78 to 6 µg/l) in the vicinity of the Limpopo River and by a factor of 6 (from 74 to 13 µg/l) in the vicinity of the Zambezi River. Concentration of Lf also decreased with depth. In the upper sediment layers lipid concentration was 0.0028-0.039% of dry matter; all mud samples were richer in lipids, than sand samples. During sedimentogenesis there is an increase in proportion of lipids relative to other classes of organic matter, proportion of low-polarity compounds increases among the lipids, and proportion of hydrocarbons rises among these compounds. Sediments inherit composition of particulate matter to the greatest degree in the vicinity of river mouths.

Petrography and geochemistry of organic matter in Triassic and Cretaceous sediments from the Wombat and Exmouth Plateau

Triassic (Carnian-Rhaetian) continental margin sediments from the Wombat Plateau off northwest Australia (Sites 759, 760, 761, and 764) contain mainly detrital organic matter of terrestrial higher plant origin. Although deposited in a nearshore deltaic environment, little liptinitic material was preserved. The dominant vitrinites and inertinites are hydrogen-lean, and the small quantities of extractable bitumen contain w-alkanes and bacterial hopanoid hydrocarbons as the most dominant single gas-chromatography-amenable compounds. Lower Cretaceous sediments on the central Exmouth Plateau (Sites 762 and 763) farther south in general have an organic matter composition similar to that in the Wombat Plateau sediments with the exception of a smaller particle size of vitrinites and inertinites, indicating more distal transport and probably deposition in deeper water. Nevertheless, organic matter preservation is slightly better than in the Triassic sediments. Long-chain fatty acids, as well as aliphatic ketones and alcohols, are common constituents in the Lower Cretaceous sediments in addition to n-alkanes and hopanoid hydrocarbons. Thin, black shale layers at the Cenomanian/Turonian boundary, although present at several sites (Sites 762 and 763 on the Exmouth Plateau, Site 765 in the Argo Abyssal Plain, and Site 766 on the continental margin of the Gascoyne Abyssal Plain), are particularly enriched in organic matter only at Site 763 (up to 26%). These organic-matter-rich layers contain mainly bituminite of probable fecal-pellet origin. Considering the high organic carbon content, the moderate hydrogen indices of 350-450 milligrams of hydrocarbon-type material per gram of Corg, the maceral composition, and the low sedimentation rates in the middle Cretaceous, we suggest that these black shales were accumulated in an area of oxygen-depleted bottom-water mass (oceanwide reduced circulation?) underlying an oxygen-rich water column (in which most of the primary biomass other than fecal pellets is destroyed) and a zone of relatively high bioproductivity. Differences in organic matter accumulation at the Cenomanian/Turonian boundary at different sites off northwest Australia are ascribed to regional variations in primary bioproductivity.

Organic matter from black shales collected in DSDP Holes 41-367 and 41-368

It is shown that microscopic algae dominate in source material of organic matter of black shales, and admixture of residues of organisms and terrestrial humic material is contained. The main direction of source material transformation during syngenesis and sedimentogenesis is associated with jellofication resulting to formation of organic matter of significantly sapropelic type. Low reflectance of vitrinite and alginite from organic matter refer to the primary and secondary lignite stages of its carbonification. Significantly sapropel type of organic matter and low stage of carbonification are reliable criteria for assigning black shales to the category of potential oil source strata.

Suspended matter on the meridional section in the Laptev Sea in August-September 1991

Suspended matter concentration along a meridian section from the Lena River delta to 78°N (~500 km) at ten stations from the surface to the bottom was studied with weight and optical (light attenuation index) techniques. At seven stations average residence time of suspended matter in surface waters was determined by the disequilibrium 234Th method. Average residence time of suspended matter in other depth intervals was calculated by regression dependence between the 234Th/238U ratio and suspended matter concentration. Differential and integral fluxes of suspended matter in the water column were also calculated. Nepheloid matter dominates in suspended matter composition in surface waters. Calculations indicate that, before being buried on the bottom, solid river run-off is resuspended 2.3 times (aver.). Redistribution of nepheloid suspended matter in the near-bottom layer results in formation of a strongly pronounced depocentre - an area of maximal discharge of solid river run-off within the Laptev Sea.

Geochemistry of labile organic matter in sediments and interstitial waters of ODP Sites 107-651 and 107-653

Sediment and interstitial water from Sites 651 and 653 (ODP Leg 107) were investigated by organic geochemical methods to characterize labile organic compound classes (amino compounds and carbohydrates) and to evaluate their progressive diagenetic and thermal degradation in deep-sea sediments. Downhole distribution of dissolved organic carbon (DOC) appears related to redox zones associated with bacterial activity and of diagenetic recrystallization of biogenic tests and not so much to organic matter concentrations in ambient sediments. DOC ranges from 250 to 8300 µmol/L (3-100.1 ppm). Amino acids contribute 10%-0.3% of DOC; carbohydrates range from 78 to 5 µmol/L. Rate of degradation of amino acids by thermal effects and/or bacterial activity at both sites (significantly different in sedimentation rates: average 41 cm/1000 yr in the top 300 m at Site 651, average 3.9 cm/1000 yr in the Pliocene/Quaternary sequence at Site 653 to 220 mbsf) is more dependent on exposure time rather than on the depth within the sediment column. Variability in neutral, acidic, and basic amino acid fractions of total amino acids (with a range of 1.1-0.02 µmol/g sediment; up to 2.5% of organic carbon) varies with carbonate content and by differences in thermal stability of amino acids. Distribution patterns of monosaccharides are interpreted to result from differences in organic matter sources, sedimentation rates, and the degree of organic matter decomposition prior to and subsequent to burial. Total particulate carbohydrates range from 1.82 to 0.21 µmol/g sediment and contribute about 8% to the sedimentary organic matter. Investigation of trace metals in the interstitial waters did not show any correlation of either DOC, amino compounds, or carbohydrates.

Composition of organic matter in bottom sediments from the Antarctic sector of the Atlantic Ocean

We identify geochemical features of sedimentary organic matter in various morphostructural zones of the Antarctic sector of the Atlantic. We present background geochemical organic parameters for shelf and deep-sea sediments from the Weddell and Scotia Seas and the Bransfield Strait. Geochemical organic parameters are good indicators of environmental and facial variations in sediments and could be used for environmental monitoring of the World Ocean.

Hydrocarbons in water, suspended matter, and bottom sediments of the White Sea

Data are presented on concentration and composition of aliphatic and polycyclic aromatic hydrocarbons (HC) in water, suspended matter (collected with a Juday net and by a separator), and in bottom sediments of the White Sea. It was found that during the last years the level of aliphatic HC concentrations in waters of the White Sea (aver. 18 µg/l) practically did not change and was comparable with average concentrations in shelf areas of the World Ocean. In water and bottom sediments distribution of HC is determined by discharge of river marginal filters. Here sedimentation of the bulk of anthropogenic HC occurs. That is why a grain-size controlling factor is not active in the zone of the river depocenter (in particular, of the North Dvina River). The same reasons most probably may explain differences in degree of geochemical relationships between contents of TOC and HC in suspended matter and bottom sediments. After passing through marginal filters natural HC are dominant in all migration forms.

Diversity and faunal composition of benthic foraminifera in Hole 44-390A on the Blake Nose Plateau

Benthic foraminiferal assemblages are a widespread tool to understand changes in organic matter flux and bottom-water oxygenation and their relation to paleoceanographic changes in the Upper Cretaceous oceans. In this study, assemblage data (diversity, total number, and number per species and gram) from Deep Sea Drilling Project (DSDP) Site 390 (Blake Nose, western North Atlantic) were processed for the lower Maastrichtian (Globotruncana falsostuarti - Gansserina gansseri Planktic Foraminiferal Zone). These data document significant changes in nutrient flux to the sea floor as well as bottom-water oxygenation during this time interval. Parallel to the observed changes in the benthic foraminiferal assemblages the number of inoceramid shells decreases, reflecting also a significant increase in bottom-water oxygenation. We speculate, that these data could reflect the onset of a shift from warmer low-latitude to cooler high-latitude deep-water sources. This speculation will predate the major reorganization of the oceanic circulation resulting in a circulation mode similar to today at the Early/Late Maastrichtian boundary by ~1 Ma and therefore improves our understanding of Late Cretaceous paleoceanography.