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.

Vertical distribution of large particulate matter in the Western Mediterranean Sea

The relationship between mesoscale hydrodynamics and the distribution of large particulate matter (LPM, particles larger than 200 ?m) in the first 1000 m of the Western Mediterranean basin was studied with a microprocessor-driven CTD-video package, the Underwater Video Profiler (UVP). Observations made during the last decade showed that, in late spring and summer, LPM concentration was high in the coastal part of the Western Mediterranean basin at the shelf break and near the continental slope (computed maximum: 149 ?g C/l between 0 and 100 m near the Spanish coast of the Gibraltar Strait). LPM concentration decreased further offshore into the central Mediterranean Sea where, below 100 m, it remained uniformly low, ranging from 2 to 4 ?g C/l. However, a strong variability was observed in the different mesoscale structures such as the Almeria-Oran jet in the Alboran Sea or the Algerian eddies. LPM concentration was up to one order of magnitude higher in fronts and eddies than in the adjacent oligotrophic Mediterranean waters (i.e. 35 vs. 8 ?g C/l in the Alboran Sea or 16 vs. 3 ?g C/l in a small shear cyclonic eddy). Our observations suggest that LPM spatial heterogeneity generated by the upper layer mesoscale hydrodynamics extends into deeper layers. Consequently, the superficial mesoscale dynamics may significantly contribute to the biogeochemical cycling between the upper and meso-pelagic layers.

(Table 2) Vertical distribution of particulate matter and its organic and mineral components in waters of the Tropical Atlantic in November 1984

Results of multiyear investigation of distribution and composition of suspended matter in waters off the northwest coast of Africa are presented. Large-scale circulation, upwelling, river runoff, and aeolian deposition affect distribution and evolution of biochemical composition of particulate matter. Concentrations of organic carbon, nitrogen, chlorophyll, phytoplankton and trace metals in the particulate matter are determined. Ratios of these components exhibit seasonal variations.

Protein and organic phosphorus in particulate matter and mesoplankton fraction in waters of the East Pacific

Vertical distribution of organic phosphorus and phosphatase activity was studied in the Southeast Pacific Ocean. The average rate of mineralization of organic phosphorus in the 0-200 m layer was shown to differ by a factor of 5-10 in oligotrophic and eutrophic areas, while residence time of phosphorus in production-destruction cycles differed by a factor of only 2-5, apparently because of both concentration of organic phosphorus and phosphorolysis rate increased simultaneously in the areas.

Carbohydrates in particulate matter of the Northwest Pacific

Patterns of distribution and variations of group and monosaccharide compositions of carbohydrates in suspended matter of the Pacific Ocean were studied. It is shown that carbohydrate content of surface ocean waters depends on reproduction of organic matter by phytoplankton. Water-insoluble polysaccharides (average 77.9% of total) predominate in composition of carbohydrates in suspended matter. Water-soluble polysaccharides and oligosaccharides were detected in considerably smaller quantities (average 12.4 and 7.3% respectively). Free monosaccharides were not detected. The main sugars in all isolated groups of carbohydrates of suspended matter are hexoses, which account for 90.8% in oligosaccharides, 64.9% in water-soluble polysaccharides, and 69.8% in water-insoluble polysaccharides. Determination of monosaccharide composition of carbohydrates in suspension showed that apparently they basically consist of mixture of reserve and structural polysaccharides (or their residues) of phytoplankton organisms.

Susupended particulate matter from the Franz Victoria Trough and its composition

In this paper authors present and discuss data on distribution and mineral composition of suspended particulate matter (SPM) in the Franz Victoria Trough, collected during Cruise 14 of scientific icebreaker Akademik Fedorov in the northern Barents Sea in October 1998. Higher total SPM concentrations (0.4-1.8 mg/l) were measured in the near-bottom layer of the Franz Victoria Strait and central part of the trough. Potential source of mineral particles in SPM is fine fractions of Barents Sea bottom sediments. They form the nepheloid layer, which spreads on the continental slope along the trough together with Barents Sea waters at 350-400 m depth.

Glycerol dialkyl glycerol tetraethers (GDGT) abundance in suspended particulate matter from the South-west and Equatorial Atlantic Ocean

The TEX86 paleotemperature proxy is based on archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids preserved in marine sediments, yet both the influence of different physiological factors on the structural distribution of GDGTs, and the mechanism(s) by which GDGTs are exported to marine sediments remain unclear. In particular, TEX86 temperatures derived directly from suspended particulate matter (SPM) in the water column can diverge strongly from corresponding in situ temperatures. Here we investigated the abundance and structural distribution of GDGTs in the South-west and Equatorial Atlantic Ocean by examining SPM collected from four surface 1000 m depth profiles spanning 48 degrees of latitude. The depth distribution of GDGTs was consistent with our current understanding of marine archaeal ecology, and specifically of ammonia-oxidizing Thaumarchaeota. Maximum GDGT concentrations occurred at the base of the primary NO2- maximum. Core GDGTs dominated the structural distribution in surface waters, while intact polar GDGTs - thought to potentially indicate live cells - were more abundant at all depths below the maximum NO2- concentration. When integrated through the upper 1000 m of the water column, > 98% of GDGTs were present in waters at and below the depth of the primary NO2- maximum. TEX86-calculated temperatures showed local minima at the depth of the NO2- maximum, while the ratio of GDGT 2:GDGT 3 [2/3] increased with depth throughout the upper water column. These results were used to model the depth of origin for GDGTs exported to sediments. By comparing our SPM data to published TEX86 values and [2/3] ratios from sediments near our study sites, we conclude that most GDGTs are exported from the depth of maximum GDGT concentrations, near the subsurface NO2- maximum (~80-250 m). This indicates that local ammonia oxidation dynamics are important regional controls on the GDGT ratios preserved in sediments. Predicting the extent to which subsurface variations in archaeal activity may influence the sedimentary TEX86 record will require a better understanding of how site-specific productivity and particle dynamics in the upper water column influence the depth of origin for exported organic matter.

Intact and core tetraether lipids in water column profiles of suspended particulate matter and of surface sediment samples off Cape Blanc, NW Africa

In the reconstruction of sea surface temperature (SST) from sedimentary archives, secondary sources, lateral transport and selective preservation are considered to be mainly negligible in terms of influencing the primary signal. This is also true for the archaeal glycerol dialkyl glycerol tetraethers (GDGTs) that form the basis for the TEX86 SST proxy. Our samples represent four years variability on a transect off Cape Blanc (NW Africa). We studied the subsurface production, vertical and lateral transport of intact polar lipids and core GDGTs in the water column at high vertical resolution on the basis of suspended particulate matter (SPM) samples from the photic zone, the subsurface oxygen minimum zone (OMZ), nepheloid layers (NL) and the water column between these. Furthermore we compared the water column SPM GDGT composition with that in underlying surface sediments. This is the first study that reports TEX86 values from the precursor intact polar lipids (IPLs) associated with specific head groups (IPL -specific TEX86). We show a clear deviation from the sea surface GDGT composition in the OMZ between 300 and 600 m. Since neither lateral transport nor selective degradation provides a satisfactory explanation for the observed TEX-derived temperature profiles with a bias towards higher temperatures for both core- and IPL -specific TEX86 values, we suggest that subsurface in situ production of archaea with a distinct relationship between lipid biosynthesis and temperature is the responsible mechanism. However, in the NW-African upwelling system the GDGT contribution of the OMZ to the surface sediments does not seem to affect the sedimentary TEX86 as it shows no bias and still reflects the signal of the surface waters between 0 and 60 m.