Phospholipids in sediments of the deep Arabian Sea

Eight different sites from 2300 to 4420 m water depth in the Arabian Sea were sampled for a biochemical quantification of phospholipid concentrations in the sediments. This method serves as a measure of microbial biomass in marine sediments comprising all small-sized organisms, including bacteria, fungi, protozoa and metazoa. Phospholipid concentrations can be converted to carbon units as an estimate of total microbial biomass in the sediments. The average phospholipid concentrations in the surface sediments (0-1 cm) of the 4 abyssal sites ranged from 7 nmol cm?3 at the southern site (SAST, 10°N 65°E, 4425 m) to 29 nmol/cm**3 at the western site (WAST, 16°N 60°E, 4045 m). The high values detected at the abyssal station WAST exceeded those in the literature for other abyssal sites and were comparable to values from the upper continental slope of the NE-Atlantic and the Arctic. At the four continental slope sites in the Arabian Sea, average phospholipid concentrations ranged from 9 to 53 nmol/cm**3 with the maximum values at stations A (2314 m) and D (3142 m) close to the Omani coast. Records of particulate organic carbon flux to the deep sea are available for four of the investigated locations, allowing a test of the hypothesis that the standing stock of benthic microorganisms in the deep sea is controlled by substrate availability, i.e. particle sedimentation. Total microbial biomass in the surface sediments of the Arabian Sea was positively correlated with sedimentation rates, consistent with previous studies of other oceans. The use of the measurement of phospholipid concentrations as a proxy for input of particulate organic matter is discussed.

Results of the sorting of the mikronekton and zooplankton material sampled by the German Antarctic Expedition 1975/1976

A description is given of the taxa sorted out of the zooplanktion and mikronekton material of the 1st German Antarctic Expedition 1975/76 by the Kiel sorting center. The methods employed in the sorting center are describined in detail. Notes for further use of the material are also given.

Uranium and thorium isotopes and sedimentation rates in metalliferous sediments from the western flank of the East Pacific Rise at 21°-22°S

Isotopic compositions of uranium (234U and 238U) and thorium (230Th and 232Th) were measured in metalliferous sediments from the western flank of the East Pacific Rise at 21°-22°S, in the area of hydrothermal activity and massive sulfide accumulation at the axis of the EPR. Concentration of 232Th (on the carbonate-free base) is consistent with composition of mafic extrusive rocks; isotope ratios 232Th/238U and 234U/238U indicate that about 70% of uranium passes into sediments from sea water with hydrothermal iron hydroxide. Mean sedimentation rates are calculated for seven cores by the nonequilibrium 230Th method with use of the constant concentration model. Flux of 230Th to bottom sediments is calculated and its mean value is used to determine sedimentation rate in four other cores. The constant flux model is used to calculate change of sedimentation rate with depth for seven cores over time interval of 100-300 ky. Sedimentation rates varied not much (0.3-0.6 cm/ky). The greatest changes occurred in two cores: one located near massive sulfide structures, and another near the spreading axis. Determinations of mean rates by the radiocarbon method and the nonequilibrium thorium method are in good agreement.

Tab.1: Total estimated muskox numbers and quotas in management zones of the Northwest Territories and Nunavut

In view of the drastic growth in the Canadian Inuit population, the rising costs of living, the missing job and income alternatives and the high unemployment rate in the arctic, efforts are being made to make use of the muskox populations in order to provide additional sources of food and/or revenue. The present paper attempts to review the course of muskox utilization in the Canadian Arctic and to tentatively assess its present as weIl as its future economic importance. Starting with the pre-European status of muskoxen in Canada, the drastic reduction in numbers resulting from the combined efforts of hide traders, whalers and expedition parties in the 19th and early 20th centuries, the impact of the legal protection and the recovery since 1917 are being described. Establishing muskox farms with semi-domesticated herds failed in Canada in the 1970's. Since 1969, though, increasing numbers of animals have been allotted to many Inuit communities, and despite the fact that most of the animals were primarily used for subsistence purposes, some communities could reserve part of their quotas for trophy (sport) hunters. While controlled sustainable subsistence and trophy hunts may eventually be carried out over the whole muskox range, including recently colonized northern Quebec, commercial harvesting for meat, hides and wool, introduced in 1981, will at least for some time be restricted to Banks and Victoria islands which at present show 78 % of the Canadian muskox population and 94 % of the overall quota.

Stable oxygen isotope data of Thoracosphaera heimii in surface sediment samples of the equatorial Atlantic and South Atlantic

To investigate the potential use of the stable isotope composition of the vegetative cysts of the photosynthetic dinoflagellate Thoracosphaera heimii for quantitative palaeotemperature reconstructions a method has been developed to purify T. heimii cysts from sediment samples. Stable oxygen and carbon isotopes have been measured on T. heimii cysts from 21 surface sediment samples from the equatorial Atlantic and South Atlantic Oceans. Calculated temperatures based on the palaeotemperature equation for inorganic calcite precipitation generally reflect mean annual temperatures of the upper water column, notably of thermocline depths. Although the present results suggest that the isotopic composition of T. heimii shells might be formed in equilibrium with the seawater in which the shells are being formed, future investigations are required to determine possible effects of metabolic and kinetic processes on the fractionation process. This pilot study therefore forms the basis for future investigations on the development of this tool and the determination of a species-specific palaeotemperature equation. The wide geographic and stratigraphic distribution of T. heimii cysts in sediments, the stable position of T. heimii within the water column and the high resistance of its cysts against calcite dissolution underline its potential for a wide usability in palaeotemperature reconstructions.