Deep Sea Research (1953)最新文献

It is suggested that the amount of heterotrophic carbon assimilation by micro-organisms in the sea may be a significant fraction of the photosynthetic production, when considering the whole water column in a deep ocean.

A method is described, allied to the carbon-14 method for measuring photosynthesis, whereby the heterotrophic uptake of any chosen substrate in sea water can be measured using the substrate labelled by carbon-14. The method is rapid and convenient and can give values of ‘relative-heterotrophic potential’. As with the radiochemical method for measuring marine photosynthesis, the exact interpretation of results presents many problems but the technique should prove a useful exploratory tool. Tests have been made using fully labelled acetate and glucose.

By a method of progressive radio-isotopic dilution it is possible to measure either the concentration or organic substrate in sea water or obtain information of the enzyme kinetics of the microorganisms assimilating a given substrate. A description is given of this method. A few preliminary trials to test its applicability have been encouraging.

Observations in the eastern Mediterranean basin confirm Pollak's suggestion (1951) that the deep water there originates in the southern Adriatic Sea by the mixing of water masses under the influence of the prevailing winter wind. This water then sinks and flows along the bottom into the eastern Mediterranean, moving counter-clockwise. Such a flow is confirmed by the distribution of oxygen in the deep water of the entire eastern Mediterranean Sea. In the western Mediterranean a deep water mass is produced at the northern end of the Algiers-Provençal basin in winter and shows a similar spread toward the south. Oxygen and phosphate concentrations indicate a low level of biological productivity throughout the year except for localized inshore regions and in the enclosed bays. The concentration of nutrients in the western basin is about twice that of the eastern basin but it is still below the concentration of the neighbouring Atlantic.

The low frequency spectra covering the ‘quiet’ range between the astronomically induced tides and the wind generated swell was obtained by an analysis of the records from three tide gauge stations along the broad Argentine shelf. The cross-spectral analyses suggest a peaked spectrum (perhaps associated with shelf-resonances) superimposed upon an independently generated spectrum which diminishes monotonically with increasing frequency. The absence of coherence between Quequen and Mar del Plata, separated by a distance of 67 nautical miles, suggests that the seiches at the two locations are not directly related in any simple way. The disturbances are not propagated as simple edge waves between the two areas.

The motions of instrumented neutral floats were measured during short tests at various locations in the North Atlantic Ocean. The vertical paths as a function of time were obtained for floats from the time they were placed in the water until well after they reached their equilibrium levels. Motions attributed to internal waves were observed on sensitively instrumented near-surface floats. Pairs of floats were found to separate rapidly with a speed which was not constant.

A pressure-gradient measuring device showed no fluctuations over a length of approximately 100 cm at depths from 200 to 700 m. The static sensitivity of the equipment was approximately 3 dyne cm⁻² mm⁻¹. Response of the device in shallower water was probably caused by gravity waves.