Hydrocarbons in surface layer bottom sediments from the North Dvina Riverand the southern part of the Dvina Bay, White Sea

Analysis of molecular composition of alkanes in bottom sediments of the southern part of Dvina Bay (White Sea) in October 2001 revealed the following main peculiarities of hydrocarbon behavior in the estuary: dominating of high molecular C23-C45 compounds and irregular distribution of hydrocarbons in bottom sediments as a result of high sedimentation rate and active hydrodynamics in the studied area.

Composition of organic matter from water, suspended matter, and bottom sediments of Nha Trang Bay, South China Sea

This research has been carried out in the Nha Trang Bay (Southern Vietnam, South China Sea) at a section from the estuary of the Cai River to the marine part of the bay, as well as in the area of coral reefs. River- and sea waters, suspended matter, and bottom sediments are studies. Data on dissolved organic carbon and total nitrogen in water are obtained. Organic carbon concentration is estimated in suspended matter; organic carbon and molecular and group compositions of n-alkanes are determined in bottom sediments. Molecular and group compositions of n-alkanes in bottom sediments of the landfill made it possible to identify three types of organic matter (OM): marine, mixed, and mainly of terrigenous origin. All these types of OM are closely related to specificity of sedimentation and hydrodynamics of waters in this area.

Eh and pH values in sediments and composition of interstitial waters from the Frolikha Bay, Baikal Lake

Redox conditions and compositions of bottom sediments and sedimentary pore waters in the area of the hydrothermal vent in the Frolikha Bay (Baikal Lake) are under discussion. According to obtained results, the submarine vent and its companion spring nearby on the land originate from a common source. The most convincing evidence for their relation comes from proximity of stable oxygen and hydrogen isotope compositions in the pore waters and spring water. The isotope composition indicates meteoric origin of the pore waters, but their major- and minor element compositions have influence of deep water, which may seep through the permeable faulted crust. Although the pore waters near the submarine vent have specific enrichment in major and minor constituents, hydrothermal discharge at the Baikal bottom causes minor influence on water composition of the Baikal Lake, unlike freshwater lakes in rifts of the East Africa and North America.

Grain size composition of sediments from the Theresa Clavenes Bay, Laptev Sea

A comparative analysis of grain size composition of shallow water terrigenous sediments from the southeastern Laptev Sea was carried out using methods developed by V.P. Petelin and A. Atterberg. Potential of these methods and possibilities of improvement of domestic techniques for grain size analysis are discussed.

Magnetic measurements performed on sediments from the Bay of Seine seafloor (France) from 2011 to 2013

Impact and monitoring of dredge spoils are an important environmental issue. This investigation aims to map two dredge-spoil dispersals in the Bay of Seine by using an innovative application of well-established environmental magnetic proxies. Low-field magnetic susceptibility measurements were performed on discrete samples from dredge sediments and from the Bay of Seine seafloor before & after dumping. The fingerprinting of the dispersion of dredge-dumped sediments is efficient due to the higher susceptibility of the dredge sediments with respect to the background. Besides, terrestrial input is also monitored in our susceptibility maps. Dilution of the susceptibility signal allows an estimation of the resilience of the sedimentary environment on a six-month survey. This susceptibility signal is controlled by the ferromagnetic fraction of the sediment. A constant magnetic mineralogy carried by magnetite is observed in the study area, thus a qualitative parameter for magnetic grain size was selected that shows an in-progress resilience pattern over the survey.

Isotopic and micropaleontological record of sediments of the Baffin Bay

The oxygen and carbon isotopic compositions of the planktonic foraminifer, Neogloboquadrina pachyderma (sinistral), were determined at 20-cm intervals through the 'composite' top ~ 22 m of sediments at ODP Site 645 (Holes 645B, 645C, 645F, and 645G) and at 10-cm intervals through a 9-m piston core (85-027-016) collected during the Hudson site survey. Quantitative analyses of palynomorphs, notably dinocysts, and of planktonic foraminifers were performed. Organic and nitrogen contents and isotopic composition of nitrogen and carbon in organic matter also were determined. These data provide a high-resolution record of changes that occurred in surface-water masses during the last glacial cycle in Baffin Bay. The basin experienced low planktonic productivity during most of the late Pleistocene, either from dilution in surface water by meltwater discharges from the surrounding ice-sheet or from the presence of a relatively dense sea-ice cover. Peaks of meltwater discharge are indicated by d18O values as low as about 1.5 per mil, correlative d13C- d18O shifts, low concentration of planktonic foraminifers, high concentrations of glacially reworked pre-Quaternary palynomorphs, and low-salinity dinocyst assemblages. As a whole, d18O values ranging between 4.5 and 2.5 per mil allow the establishment of an 18O stratigraphy spanning isotopic stages 5 to 1. Because of the poor core recovery, the general paucity of microflora and microfauna, and the possible occurrence of slumping or debris flow at Site 645, further interpretation remains problematic.

Bivalve mollusks in the sediments of the Anapa Bay Bar (Black Sea) in October 2010

Sandy beaches of the Anapa Bay Bar are a unique natural resource, but they are gradually being degrade under both natural and anthropogenic factors. Emissions of sand and shelly ground from the adjacent sea bottom partly compensate for this process. Concentration of carbonates may reach up to 50% in beach sands, and most of these carbonates are of mollusk origin. The major deposit formation role belongs to the key bivalve species: Chamelea gallina (Linnaeus, 1758). Average biomass of this mollusk species reaches up to 450 g/m**2 at depths 5-10 m. The other two subdominating mollusk species, bivalve Donax trunculus (Linnaeus, 1758) and gastropod Rapana venosa (Valenciennes, 1846), may impact as 16 g/m**2 and 6 g/m**2, respectively. Annually, 350 kg of shelly ground per running meter are newly deposited on the Anapa beach.

Chlorophyll and true-color maps of sediments from the intertidal zones in Winyah Bay, South Carolina, USA and List, Sylt, Germany

We used hyperspectral imaging to study short-term effects of bioturbation by lugworms (Arenicola marina) on the surficial biomass of microphytobenthos (MPB) in permeable marine sediments. Within days to weeks after the addition of a lugworm to a homogenized and recomposed sediment, the average surficial MPB biomass and its spatial heterogeneity were, respectively, 150 - 250% and 280% higher than in sediments without lugworms. The surficial sediment area impacted by a single medium-sized lugworm (~4 g wet weight) over this time-scale was at least 340 cm**2. While sediment reworking was the primary cause of the increased spatial heterogeneity, experiments with lugworm-mimics together with modeling showed that bioadvective porewater transport from depth to the sediment surface, as induced by the lugworm ventilating its burrow, was the main cause of the increased surficial MPB biomass. Although direct measurements of nutrient fluxes are lacking, our present data show that enhanced advective supply of nutrients from deeper sediment layers induced by faunal ventilation is an important mechanism that fuels high primary productivity at the surface of permeable sediments even though these systems are generally characterized by low standing stocks of nutrients and organic material.

Age determination of Paleogene sediments from the Prysz Bay

Age dating of Paleogene diamictites from ODP Site 739 in Prydz Bay with marine microfossils (diatoms and calcareous nannofossils) suggests the build-up of a major East Antarctic ice shield in latest Eocene to earliest Oligocene time, about 35-38 m.y. ago. Strontium isotopic analyses of small mollusk remains found within these diamictites, however, yield younger ages ranging from 29 to 23 Ma (i.e., latest early Oligocene to earliest Miocene). These age discrepancies could be caused by repeated glacial reworking of microfossils, macrofossils, and sediment clasts through the late Oligocene or, alternatively, by ion exchange in the still aragonitic mollusk shells.

Chemistry of organic matter of glacial and Cretaceous sediments from the Prydz Bay

Organic matter in Miocene glacial sediments in Hole 739C on the Antarctic Shelf represents erosional recycled continental material. Various indications of maturity in bulk organic matter, kerogens, and extracts imply that an exposed section of mature organic carbon-rich material was present during the Miocene. Based on biomarker, n-alkane, and kerogen analysis, a massive diamictite of early Eocene/Oligocene age at Hole 739C contains immature organic matter. Visual and pyrolysis analyses of the kerogens suggest a predominance of terrestrial organic matter in all samples from Hole 739C. A reversal of thermal maturities, i.e., more-mature overlying less-mature sections, may be related to redeposition generated from glacial erosion. Siliciclastic fluviatile sediments of Lower Cretaceous age from Hole 741A were analyzed. The organic matter from this hole contains immature aliphatic and aromatic biomarkers as well as a suite of odd carbon number-dominated nalkanes. Visual examination and pyrolysis analysis of the kerogen suggests that predominantly immature terrestrial organic matter is present at Hole 741A. The similarities between Hole 739C Unit V and Hole 741A suggest that the source of the organic matter in the glacial sediments in Unit V at Hole 739C could be Cretaceous in age and similar to sediments sampled at Hole 741A in Prydz Bay.

Sulfur concentrations and isotope ratios in sediments from Kiel Bay, western Baltic Sea

The isotope-ratios of sulfur-components in several sedimentologically different cores of recent marine sediments from Kiel Bay (Baltic Sea) were investigated. In addition, quantitative determinations were made on total sulfur, sulfate, sulfide, chloride, organic carbon, iron and watercontent in the sediment or in the pore-water solution. The investigations gave the following results: 1. The sulfur in the sediment (about 0.3 -2 % of the dry sample) was for the most part introduced into the sediment after sedimentation. This confirms the results of Kaplan et al. (1963, doi:10.1016/0016-7037(63)90074-7). The yield of Sulfur from organic material is very small (in our samples about 5-10% of the total sulfur in the sediment). 2. The sulfur bound in the sediment is taken from the sulfate of the interstitial water. During normal sedimentation, the exchange of sulfate by diffusion significant for changes in the sulfur-content goes down to a sediment depth of 4-6 cm. In this way the sulfate consumed by reduction and formation of sulfide or pyrite is mostly replaced. The uppermost layer of the sediment is an partly open system for the sulfur. The diagenesis of the sulfur is allochemical. 3. The isotope-values of the sediment-sulfur are largely influenced by the sulfur coming into the sediment by diffusion and being bound by bacteriological reduction. Due to the prevailing reduction of 32S and reverse-diffusion of sulfate into the open sea-water, an 32S enrichment takes place in the uppermost layer of the sediment. delta34S-values in the sediment range between -15 and -35 ? while seawater-sulfate has +20 ?. No relationship could be established between sedimentological or chemical changes and isotope-ratios. In the cores, successive sandy and clayly layers showed no change in the delta-values. The sedimentation rate, however, seems to influence isotope-ratios. In one core with low sedimentationrates the delta34S-values varied between -29 and -33 ?, while cores with higher sedimentationrates showed values between -17 and -24 ?. 4. As sediment depth increases, the pore-water sulfate shows decreasing concentrations (in a depth of 30-40 cm we found between 20 and 70 % of the seawater-values), and increasing delta 34S-values (in one case reaching more than +60 ?). The concentration of sulfide in the pore-water increases with sediment-depth (reaching 80 mg S/l in one case). The (delta34S-values of the pore-water-sulfide in all cores show increases paralleling the sulfate sulfur, with a nearly constant delta-distance of 50-60 ? in all cores. This seems to confirm the genetic relationship between the two components.

Thorium and uranium isotopes in upper Pleistocene sediments of the Baffin Bay

Concentrations and activity ratios of uranium and thorium isotopes (234U/238U, 230Th/232Th) were determined at about 5-m intervals through the composite top 22-m sequence of Ocean Drilling Program (ODP) Hole 645 in Baffin Bay and, in the Labrador Sea, at 1-m intervals through the top 11 m of Core 84-030-003 (TWC and P) collected by the Hudson during a preliminary survey of Site 647, and also at about 2-m intervals through the composite top 22-m sequence of Hole 646. In the Labrador Sea, surficial sediments show unsupported 230Th having a 230Th/234U activity ratio of about 3. At Site 647, a regular decrease in the 230Th/232Th activity ratio was observed downcore from about 1.2 (at 1 mbsf) to about 0.4 (at ~8 mbsf), through a sequence spanning over 18O stages 2 through 8. The correlative thorium/uranium chronology and 18O stratigraphy indicate relatively constant sedimentation rates throughout the sequence. At Site 646, down Greenland slope, and at Site 645, in Baffin Bay, highly variable uranium and thorium concentrations and isotopic ratios were observed in relation to highly variable sedimentation rates. As a whole, the lower-excess observed in Baffin Bay records is indicative of very high absolute sedimentation rates in comparison with those of the Labrador Sea. These rates are confirmed by the 18O-stratigraphy and a few AMS 14C controls on handpicked foraminifers. At both Labrador Sea sites, a clear indication of an initial 230Th-excess (over the 230Th-rain from the water column) was found.