ALBERT

Beschreibung: Energy dispersive X-ray microanalysis was used to localize the two brominated natural products (aerothinonin and homoaerothionin) in the tissues of a marine demosponge, Aplysina fistularis. Virtually all of these compounds were localized within the spherules of the spherulous cells in the mesohyl. This is the first localization of any secondary metabolite at the cellular or sub-cellular level in any marine invertebrate. In Aplysina fistularis, as in other species of the same genus studied by Vacelet, the spherulous cells are concentrated just beneath the exopinacoderm and just beneath the endopinacoderm of the excurrent canals. Moreover, there is electron microscopic evidence for degeneration of some spherulous cells throughout the mesohyl. Presumably, this degeneration can release some aerothionin and homoaerothionin, which are known to have antibiotic properties. After release from the spherulous cells, these brominated natural products could function (1) within the mesohyl to exclude some types of bacteria or to aggregate ingested bacteria and/or (2) within the boundary layer of the surrounding seawater for defense or offense, as considered in the discussion section.

Beschreibung: Current and wind stress time series obtained from the F1-mooring are analysed with the aim of examining linear correspondences and testing the adequacy of linear coupling models at near-inertial frequencies. Significant linear correlations are found in the data set which are consistent with a linear winddriven model of the current system. The current in the mixed layer can be described by inertial oscillations directly forced by the local wind stress. A wind-driven simulation model of the mixed layer currents yields an energy input of 3.10-3 W/m2. The current in the thermocline can be described by a linear internal wave field of downward propagating wave groups driven via Ekman suction by the wind stress field. Internal waves are generated at a rate of 10-3 W/m2, consistently estimated from both kinematic and dynamic considerations.

Beschreibung: Existing information is synthesized and new data presented to describe the flow of near-bottom water from the Weddell Sea into the Scotia Sea and westward through Drake Passage along the continental slope. The water characteristics and currents along the northern margins of the South Sandwich Island Arc are examined. Long-term current measurements in the bottom waters at locations over the outer shelf and slope and along the continental rise show persistent flow from Atlantic to Pacific along isobaths at speeds of 10–20 cm s−1. Three sources for the waters in these currents are identified and discussed. At the deepest levels, Weddell Sea Deep Water enters the Scotia Sea near 40°W through a depression in the South Scotia Arc and then flows westward, constrained by the bottom topography. This cold, fresh, oxygenated bottom water then flows west to enter Drake Passage via a gap in the Shackleton Fracture Zone at the base of the continental slope northwest of Elephant Island. Mid-depth water may flow from the Weddell Sea to the Scotia Sea through the Powell Basin (sill depth approximately 2000 m) located west of South Orkney Island near 48°W. The westward flowing waters along the shelf and upper continental slope, which are denser than those immediately offshore, may be a continuation of the Polar Slope Current from the Weddell Sea or may be derived principally by convection from the shelves of the South Sandwich Island Arc. A vertical section north of Elephant Island shows downslope convection off the shelf, analogous to the observed at many locations around Antartica.

Beschreibung: During a multi-institutional air-sea interaction experiment (GATE) in the central Atlantic North Equatorial Countercurrent in September 1974, vector-averaging current meter (VACM) measurements were made within the 30-m thick mixed layer from three different types of surface moorings. The moorings consisted of a single-point taut-line flexible mooring (E3), a spar-buoy (El), and a 2-legged mooring (Fl). Although the kinetic energy density spectral estimates of the E3, El, and Fl records in the low frequency range were equivalent with 95% confidence, the mean progressive vector diagrams differed by 6 % in length and 4 in direction. At frequencies above 1 cph the variances of the 7.2 m Fl current vectors were about 1.5 times larger than the 7.6 m E3 data and the spectral levels of the 20 m El and 21.4 m E3 record were equivalent, suggesting that VACM current vectors recorded near the surface beneath a surface-following buoy do not contain detectable amounts of aliased high-frequency mooring motion.

Beschreibung: The maximum counterillumination intensities of three species of mesopelagic squids and one species of mesopelagic fish were determined in a shipboard laboratory. The values were compared with the intensity of downwelling irradiance in the ocean measured off Oahu, Hawaii. The upper depth limits of the mesopelagic fauna were determined by mid-day and moonlit-night trawling. The data support the hypothesis that limits on concealment from predation through counterillumination determine the upper depth limits of this fauna during the day. At night near full moon, however, animals may be found at light levels higher than those at which counterillumination seems to be an effective strategy.