Stable oxygen isotope record of corales from the Red Sea

In order to assess the ability of Porites corals to accurately record environmental variations, high-resolution (weekly/biweekly) coral delta18O records were obtained from four coral colonies from the northern Gulf of Aqaba, which grew at depths of 7, 19, 29, and 42 m along one transect. Adjacent to each colony, hourly temperatures, biweekly salinities, and monthly delta18O of seawater were continuously recorded over a period of 14 months (April 1999 to June 2000). Contrary to water temperature, which shows a regular and strong seasonal variation and change with depth, seawater delta18O exhibits a weak seasonality and little change with depth. Positive correlations between seawater delta18O and salinity were observed. The two parameters were related to each other by the equation delta18O Seawater (per mil, VSMOW) = 0.281 * Salinity - 9.14. The high-resolution coral delta18O records from this study show a regular pattern of seasonality and are able to capture fine details of the weekly average temperature records. They resolve more than 95% of the weekly average temperature range. On the other hand, attenuation and amplification of coral seasonal amplitudes were recorded in deep, slow-growing corals, which were not related to environmental effects (temperature and/or seawater delta18O) or sampling resolution. We propose that these result from a combined effect of subannual variations in extension rate and variable rates of spine thickening of skeletal structures within the tissue layer. However, no smoothing or distortion of the isotopic signals was observed due to calcification within the tissue layer in shallow-water, fast-growing corals. The calculations from coral delta18O calibrations against the in situ measurements show that temperature (T) is related to coral delta18O (delta c) and seawater delta18O (delta w) by the equation T (°C) = -5.38 (delta c - delta w) -1.08. Our results demonstrate that coral delta18O from the northern Gulf of Aqaba is a reliable recorder of temperature variations, and that there is a minor contribution of seawater delta18O to this proxy, which could be ignored.

Phytoplankton of the southwest Kara Sea on August 9-12, 2007

A research was carried out along a transect from the Yamal Peninsula coast towards the outer shelf of the southwestern the Kara Sea in September 2007. 130 phytoplankton species were identified, among which 63 were found in the area for the first time. Total phytoplankton abundance varied from of 0.2 x10**9 to 11.3x10**9 cells/m**2, while biomass from 43 to 1057 mgC/m**2. A well pronounced cross-shelf zoning in phytoplankton communities was ascertained. The inner shelf zone about 30 km wide with depths down to 30 meters was characterized by predominance of diatoms (up to 80% of total algal abundance and biomass). The second group by value was dinoflagellates. Seaward in the area of depth increase from 30 to 140 m, the zone of the Yamal Current was located, which was 40 km wide and notable for its active water dynamics. Total abundance in the zone was maximal for the entire investigated area: up to 11.3x10**9 cells/m**2. Autotrophic flagellates were the leading group in phytoplankton, their share in total abundance reached 56-82%. Further than 70 km from the shore, the outer shelf zone was found with the water column rigidly stratified. The highest for the whole area phytoplankton biomass was identified here (up to 1.06 gC/m**2), 80% of which concentrated above the halocline. Diatoms dominated in phytoplankton abundance (up to 92%) and biomass (up to 90%) that resulted from mass development of two species: Chaetoceros diadema and Leptocylindrus danicus.

Composition of surface layer bottom sediments from the Chukchi Sea

Abundance of noble metals and bulk chemical composition have been studied in bottom sediments of the Chukchi Sea. Distribution of noble metals and their correlation with major and trace elements in the sediments have been analyzed using multicomponent statistics. It was established that average contents of noble metals in the bottom sediments of the Chukchi Sea significantly exceed those both in shelf terrigenous sediments and stratisphere. Osmium and iridium enrich mixed and pelitic sediments relative to shallow-water sediments and their influx is presumably determined by erosion of coastal and bottom unconsolidated deposits. High Ag, Ru, Au, and Pt contents were identified in clayey sediments enriched in biogenic elements in the some areas of the Southern Chukchi plain (Chukchi Sea) confined to intersection zones of submeridional and sublatitudinal structures of the graben-rift system, which formed in Mesozoic and activated in Late Cenozoic.