Deep Sea Research and Oceanographic Abstracts最新文献

This is the first known report of the midwater capture of a species of macrourid that lives on the abyssal plain. Four Coryphaenoides filifer were caught in an Isaacs-Kidd midwater trawl over 500 m above the 2700- to 2800-m sea floor in the northeastern Pacific Ocean off central Oregon. Such behavior helps to explain the presence of pelagic organisms in the stomachs abyssobenthic macrourids and may accelerate transport of energy and elements to the deep-sea benthos.

The sampling characteristics of these instruments can be improved to the extent that simple design criteria are satisfied: minimal long axis and mesh pressure, maximal flow through the recorder. Two new systems are described which appear to give improved performance and have been used operationally at sea. One is a small system for use on vessels with restricted deck space, the other a larger system fitted with a new recorder ☐ having a very large filtering area and active backward water transport achieved with an impeller system. It is also suggested that studies of vertical biotic structure are better performed with oblique, rather than vertical, LHPR hauls.

In future prospecting for manganese nodules it will be more and more necessary to have information on board a ship, both for large- and small-scale prospections. It is the purpose of this paper to present two types of instruments for chemical analysis of manganese nodules, already used on board, and which can be each considered as a function of required precision and ship capabilities. One is a dispersive X-ray fluorescence instrument, the other a non-dispersive X-ray fluorescence analyser; the two methods involve simple sample preparation with measurements being made from powdered samples or pellets.

In July 1973 the whole FAMOUS (French-American Mid-Ocean Undersea Study) area was surveyed using a long-range side-scan sonar (GLORIA). The mosaic of sonographs which was produced shows two sets of mainly linear targets. These targets can be related to locally steep scarps on the sea-floor and ate interpreted as the scarps of steep faults. The fault scarps comprising the larger set are tens of kilometres long and subparallel to the median valley but tend to be curved in plan near fracture zones. The most satisfactory explanation for these is that they are formed by caldera-collapse over an elongate cigar-shaped magma chamber which lies beneath the inner floor of the median valley. The fault scarps of the other set occur only in fracture zone valleys and run obliquely to the general trend of the transform fault zone. They appear to be subsidiary strike-slip and normal faults generated within the zone of shear which characterizes a transform fault. Our results indicate that the upper crust of a slow-spreading ridge is faulted into long narrow parallel-sided slices within the inner floor, probably by the faults which produce the inner walls of the median valley.

Ultrafiltration has been used to concentrate dissolved organic macromolecules from seawater. Partial characterization of the macromolecular material shows that it differs markedly from its supposed biological source materials. Changes in the amounts in different molecular weight fractions with depth seem to define several layers. The significance of these changes in light of current theories of the nature and cycling of organic matter in the sea is discussed.

Based on opening-closing net plankton collections, the vertical and horizontal distributions of some triplyean radiolarian species have been plotted for the eastern North Pacific. In a mid-ocean profile of the upper 400 m, there emerge: (1) a zone including subarctic near-surface waters and extending southward at greater depths, (2) a narrow zone to the south concentrated above the first zone, and (3) a zone yet farther south ranging from the surface to a lower boundary that shoals northward. These zones correspond generally to the following respective hydrographic features: (1) the Subarctic Water Mass and the Intermediate Water, centered on a salinity minimum, (2) an unnamed mid-latitude zone characterized by a salinity maximum above the salinity minimum and (3) the warm, high salinity, Central Water Mass. Toward the North American continent, distributions of species from the two more northern (and deeper) zones overlap as the respective water masses become mixed in the California Current. The southernmost (and shallowest) zone retains hydrographic and biologic continuity as a surface layer at the outer edge of the California Current. Semi-closed circulation systems in the hydrographic zones provide physical and biological continuity within the zones with minor interchange among them.

The horizontal distributions of these radiolarians in the upper 150 m are comparable to those of other kinds of plankton in the same area, and they are generally consistent, hydrographically, with previously reported distributions of the same species in other oceans.

Temperature and temperature-gradient records made as a freely-falling probe hit bottom show an extremely well-mixed layer on the Oregon continental shelf in September, 1974. Temperatures were uniform to within a few millidegrees in a 10-m deep layer. A reverse gradient of one to four times the adiabatic was found in the last 5 m or so, larger than the geothermal flux could maintain. The layer depth is similar to that of a turbulent Ekman layer. On vertical temperature-gradient spectra several subranges are seen. Estimates of eddy diffusivity by the Cox-Osborn-Hacker method agree within a factor of two with estimates calculated from the level of an assumed inertial sub-range in temperature gradient spectra. Possibly the layer is stabilized by a salinity gradient too small to be observed by the conductivity-temperature-depth probe, or by sediment load. Calculations of heat flux caused by the thermal storage of the sediments yield a flux of the correct order, but the opposite sign, of the calculated flux.