ALBERT

Description: The effect of medium dissolved-oxygen tension on the molar growth yield, respiration and cytochrome content of Beneckea natriegens in chemostat culture (D 0·37 hr-1) was examined. The molar growth yield (Y), the specific rate of oxygen (qo2) and glucose consumption, and the specific rate of carbon dioxide evolution were independent of the dissolved-oxygen tension above a critical value (〈 2 mmHg). However, the potential respiration rate increased with reduction in the dissolved-oxygen tension at values of the dissolved-oxygen tension well above the critical value. Changes in the cytochrome content occurred at dissolved-oxygen tensions well above the critical value. An increase in cytochrome c relative to cytochrome b was observed as the dissolved-oxygen tension was decreased. Reduction of the dissolved-oxygen tension to less than 1 mmHg caused a switch to fermentative metabolism shown by the apparent rise in Y o2 and decrease in the molar growth yield from glucose. At this point the potential respiration rate (q o2) increased to its highest value, while the cytochrome pattern reverted to that observed at dissolved-oxygen tensions above 96 mmHg. There appeared to be no correlation between cytochrome content, potential q o2, in situ q o2, and cyanide sensitivity of the organism at various dissolved-oxygen tensions.

Description: Permeability of a large number of natural marine sediment samples from the Gulf of Mexico was determined through the use of laboratory consolidation tests. The samples were divided into the following groups: Group 1, sediment consisting of more than 80% clay (material 2 μm or less in size); Group 2, sediment containing from 60 to 80% clay‐size material; Group 3, silty clays with less than 60% clay; and Group 4, silts and clays that have a significant sand‐size fraction present (more than 5% sand). The permeabilities of the groups ranged from 10−5 to 10−10 cm/s with 35% normal seawater being used as the saturating fluid. A statistical analysis of the natural log of permeability versus porosity was used to develop the permeability prediction equation for each of the groups listed. The equation for Group 1 is k =en(15.05)‐27.37. for Group 2, k=en(14. 18)‐26.50. for Group 3, k= en(15.59)‐26.65. for Group 4 k=en(17.51)‐26.93.and for all data, k = en(14.30)‐26.30; wherc n is the porosity (in decimals) and k is the coefficient of permeability. These equations are useful for predicting changes in permeability with depth in fine‐grained sediments of the Gulf of Mexico. The ability to predict permeability in a continuous sequence, where the deposition history is known, may explain the large variations that we see in the physical properties in sediments similar in grain size and mineralogy.

Description: Little work on vertical distribution of cephalopods was possible before the development, in the 1960s, of sophisticated opening-closing devices usable on midwater trawls such as the 10 ft Isaacs Kidd trawl (IKMT; Foxton, 1963; Aron et al. 1964) and the series of rectangular midwater trawls developed by the Institute of Oceanographic Sciences (previously the National Institute of Oceanography) (Clarke, 1969 a; Baker et al. 1973). These developments have resulted in three papers on vertical distribution of cephalopods in the North Atlantic (Clarke, 1969 ft; Gibbs & Roper, 1970; Clarke & Lu, 1974) and one for the Mediterranean (Roper, 1972). The present paper describes the vertical distribution of cephalopods caught at 40° N 20° W, 53° N 20° W and 60° N 20° W in the North Atlantic based upon day and night series of horizontal hauls between the surface and 2000 m using the RMT combination net (Baker et al. 1973).

Description: The present work is part of an analysis of catches made with rectangular midwater trawls (RMTs) in the North Atlantic at about 20°W and at 60°N, 53°N, 40°N (all in Lu & Clarke, 1975), 30°N (Clarke & Lu, 1974), 18°N and 11°N (Lu & Clarke, 1975). The collections were made for the ecological programme of the National Institute of Oceanography, Wormley, England (now part of the Institute of Oceanographic Sciences).

Description: This is one of a series of four papers dealing with vertical distribution of cephalopods in the North Eastern Atlantic at six stations near 20° W and at about 10° intervals from 60°N to 11° N (Clarke & Lu, 1974, 1975 a; Lu & Clarke, 1975). The present study is based upon a series of hauls made at discrete horizons between o and 2000 m with opening-closing nets during both daylight and darkness. The collections were made for the ecological programme of the National Institute of Oceanography, Wormley, Surrey, England (now part of the Institute of Oceanographic Sciences).

Description: A model for interstitial silica concentrations is derived, incorporating biological mixing of sediments. This model predicts concentrations and gradients and can account for the observed geographical variations in interstitial silica on the basis of a dynamic balance between solution of silica particles and diffusion from the sediments. The flux of particulate biogenous silica into the sediments is confirmed as an important parameter controlling interstitial silica concentrations. Biological mixing of sea floor sediments also has an important influence on interstitial composition by modifyirig the depth at which dissolving particles react. Faster mixing raises the interstitial concentration. The rate at which siliceous particles dissolve also plays a role; the slower they dissolve, the greater the interstitial silica concentration. Measurements on near‐bottom waters of the Atlantic show no consistent gradients in dissolved silica, but antarctic bottom water seems significantly more variable in the benthic boundary layer than in the water mass above or in the benthic zone of North Atlantic deep water.

Description: Biological mixing in deep‐sea sediments is described in terms of a time‐dependent eddy diffusion model where mixing takes place to a depth L at constant eddy diffusivity D. The differential equation that describes this model has been solved for an impulse source of tracer delivered to the plane surface that forms the top of the mixed layer. The solution then serves as a Green's function, which can be used to determine the distribution of tracer in depth and in time for a surface input of tracer specified as any arbitrary function of time. The characteristic properties of the solution are dependent on the dimensionless parameter D/Lυ, where υ is the sedimentation rate. If D/Lυ is greater than 10, the surface layer becomes homogeneous, and the model is identical to the homogeneous layer model proposed by Berger and Heath (1968). If D/Lυ is less than 0.1, little mixing can take place before the sediments are buried, and so the surface concentration propagates downward into the sediments with little dispersion. For all values of D/Lυ the weighted mean depth of the concentration distribution is the depth at which an impulse source would be found in the sediment if no mixing had taken place. The microtektite data of Glass (1969, 1972) and Glass et al. (1973) indicate that abyssal sediments are mixed from the surface to a maximum mixing depth that ranges between 17 and 40 cm below the surface. Mixing occurs at rates between 1 and 100 cm2 kyr−1. Higher mixing rates may occur nearer the surface, but microtektite distributions cannot be used to estimate these rates in the presence of the deeper, slower mixing. Estimates for D based on dimensional analysis of sediment reworking rates for nearshore organisms (103–106 cm2 kyr−1) are used to predict abyssal mixing rates between 1 and 103 cm2 kyr−1 by invoking the assumption that mixing is proportional to biomass. Plutonium distributions in deep‐sea sediments (Noshkin and Bowen, 1973) indicate abyssal mixing rates ranging from 100 to 400 cm2 kyr−1.