The effect of currents on the generation of internal waves by a barotropic tide near an underwater ridge

In the frame of the linear theory for long waves, the paper studies long waves generated by a barotropic tide running at an arbitrary angle over a bottom ridge. The ocean is assumed to be two-layered. In the area of a ridge with a rectangular cross section, geostrophic flows are considered, coupled with the inclinations of the free surface and interface. Wave amplitudes are shown to depend on the angle of an onrunning tide and this allows us to reach a conclusion about the influence of a geostrophic current on the generation of internal waves. Translated by Vladimir A. Puchkin.     

Gravity torques for surface waves

The effects of the gravity torques acting on the angular momentum of surface gravity waves are calculated theoretically. For short crested waves the gravity torque is caused by the force of gravity on the orbiting fluid particles acting down the slopes of the crests and troughs and in the direction parallel to the crests and troughs. The gravity torque tries to rotate the angular momentum vectors, and thus the waves themselves, counterclockwise in the horizontal plane, as viewed from above, in both hemispheres. The amount of rotation per unit time is computed to be significant assuming reasonable values for the along-crest and trough slopes for waves in a storm area. The gravity torque has a frequency which is double the frequency of the waves. For long crested waves the gravity torque acts in the vertical plane of the orbit and tries to decelerate the particles when they rise and accelerate them when they fall. By disrupting the horizontal cyclostrophic balance of forces on the fluid particles (centrifugal force versus pressure force) the gravity torque accounts qualitatively for the three characteristics of breaking waves: that they break at the surface, that they break at the crest, and that the crest breaks in the direction of wave propagation.     

Prediction of hydrological phenomena using self-organizing mathematical models

The paper considers the application of self-organizing models, specifically, the method of grouped arguments consideration (MGAC), to forecast short and non-stationary time series of observations in the ocean. A sequence of operations for the treatment of observational series is suggested. To assess its efficiency, we have used mean monthly oxygen concentration data collected in the surface and near-bottom layers of the Taganrog Bay. It is shown that the application of the MGAC model allows one to reduce by two times the root-mean-square error of that of the series prediction by five points, in comparison with the Jenkins-Box regressional model. It has been concluded that the predictors' non-linear functions may be effectively used in the treatment of short samplings. Translated by Vladimir A. Puchkin.     

Primary production and plankton stocks in the Pacific Ocean and their seasonal variation according to remote sensing and field observations

Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year⁻¹. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year⁻¹. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant.     

On the origin of glauconitic and chamositic granules

Glauconitic minerals range from green smectite to 10Å glauconite, occur mainly in peloids (most of which were fecal pellets), and apparently were produced largely by neoformation replacing several kinds of substrate. Chamositic minerals, berthierine and chamosite, occur in Recent and ancient peloids, but mostly in ancient ooids, and they developed by alteration of a precursor Al-rich clay mineral. Ooid sheaths were built by rolling of cores on ue sea floor. Glauconitic greensands and chamositic oolitic ironstones are condensed sequences deposited as sandwaves during long periods of reduced influx of sediment. Some are associated with hardgrounds.     

Alkaline Phosphatase Activity in the Red-Tide Dinoflagellate, Ptychodiscus brevis

Abstract. Alkaline phosphatase activity (APA) was found in a nearshore, natural population of the red-tide dinoflagellate Ptychodiscus brevis. Initial hydrolysis rates were enhanced by two orders of magnitude within 24 h upon addition of ammonium. Other nutrient (additions) or no additions also lead to a higher, although less pronounced increase in activity. Enhanced growth after nutrient additions combined with specific APA indicated that the bloom was both N and P limited. Since the natural population was a mixture of diatoms and the dinoflagellate, APA was also measured in unialgal cultures of P. brevis. APA was not reduced but enhanced by the addition of low concentrations of orthophosphate (0.5 and 1 μM). Higher orthophosphate concentrations (5 to 20 μM) reduced APA, although activity returned to control levels within 2 to 6h. Repression occurred within 30 sec after a 20 μM orthophosphate addition. Cells which had APA repressed by an orthophosphate addition regained their initial activity within 2 h after washing with phosphate-free media. Phosphorus-deficient cells of P. brevis possess an alkaline phosphatase system which is capable of continued activity at low in situ orthophosphate levels.     

An ecosystem model with iron limitation of primary production in the equatorial Pacific at 140°W

We construct a one-dimensional ecosystem model (nitrate, ammonium, phytoplankton, zooplnakton and detritus) with simple physics and biology in order to focus on the structural relations and intrinsic properties of the food web that characterizes the biological regime in the central equatorial Pacific at 140°W. When possible, data collected during the EgPac and other cruises were used to calibrate model parameters for two simulations that differ in the limiting nutrient, i.e. nitrogen or iron. Both simulations show annual results in good agreement with the data, but phytoplankton biomass and primary production show a more pronounced annual variability when iron is used as the limiting nutrient. This more realistically reproduces the variability of biological production and illustrates the greater coupling between vertical physical processes and biological production when the limiting nutrient is iron rather than nitrogen. The iron simulation also illustrates how iron supply controls primary production variability, how grazingbalances primary production and controls phytoplankton biomass, and how both iron supply and grazingcontrol primary production. These results suggest that it is not possible to capture primary production variability in the central equatorial Pacific with biological models using nitrogen as the limiting nutrient. Other indirect results of this modeling study were: (1) partitioning of export production between dissolved and particulate matter is almost equal, suggesting that the importance of DOC export may have been previously overestimated; (2) lateral export of live biomass has to be taken into account in order to balance the nitrogen budget on the equator at 140°W; and (3) preferential uptake of ammonium (i.e. nitrate uptake inhibition by ammonium) associated with high regeneration of nitrogen (low f ratio as a consequence of the food web structure imposed by iron limitation) largely accounts for the surface build-up of upwelled nitrate.     

The effects of light and nutrients on rates of ammonium transformation in a eutrophic river

Rates for nitrification, phytoplankton uptake of ammonium, and regeneration of ammonium were measured in the Delaware River as functions of irradiance and nutrient concentrations, using ¹⁵N labeling methods. Phytoplankton uptake increased and nitrification rates declined with increased light intensity. The irradiance level required for maximum uptake by phytoplankton was similar to that for maximal inhibition of nitrification (about 300μEm⁻² s⁻¹). Daily, water-column averaged rates, calculated by integration of the observed rate-intensity relationships, indicate that light plays a key role in regulating the balance between oxidation of NH₄⁺ by bacteria and assimilation by phytoplankton in the Delaware. The results show that uptake of ammonium by phytoplankton in the dark may exceed uptake in the light in optically thick systems.     

The toxicity of one-hour silver exposures to early-life stages of the surf Spisula solidissima (Dillwyn)

Early life stages of Spisula solidissima (1-, 4-, 8- and 12-h post-fertilization) were exposed to various concentrations of silver in solution (0, 4, 8, 24, 44, 124 and 278 μg liter^?1) for 1 h. An additional group of 1-h post-fertilized eggs was treated with 0, 4, 11 and 24 μg liter^?1 silver continuously for 48h. Results indicate that younger embryos are more susceptible to Ag. Exposure of one-hour-old embryos to silver for only 1 h gives results similar to a continuous 48-h exposure to the same concentration of Ag. The calculated EC₅₀ for 48-h continuously exposed embryos was similar to the EC₅₀ for 1-h post-fertilized embryos that were exposed to silver for only 1 h.     

The bottom currents in the area of abyssal hills in the north-east tropical Pacific Ocean

The results of simultaneous measurements of the bottom (6.25 and 35 m above the bottom) currents, deep currents, and surface currents made at three points in the north-east tropical Pacific Ocean are given. The bottom intensification of the current velocity is revealed in a layer of 35–25 m above the bottom. The estimation of the thickness of the bottom boundary layer (BBL) indicates that the velocity intensification is observed over the boundary layer upper border. A 10-day long benthic storm with a maximum measured velocity of 13 cm/s was revealed 6 m above the bottom. As was found, the origin of the benthic storm is associated with the penetration of an anticyclonic eddy down to the bottom.Translated by Mikhail M. Trufanov.