Live (stained) benthic foraminifera from the Rhône prodelta (Gulf of Lion,NW Mediterranean): Environmental controls on a river-dominated shelf

In this paper, we investigate the ecology of live (rose Bengal stained) benthic foraminifera collected at 20 stations ranging from 15 to 100 m depth in the Rhône prodelta (Gulf of Lions, NW Mediterranean). These sites were sampled in September 2006, five months after the Rhône River annual flood. Statistical analyses based on foraminiferal communities (> 150 μm) divide our study area into six main biofacies directly related to environmental conditions. Miliolid species are abundant in the relict prodeltaic lobe which is characterised by sand with low organic matter content. Close to the river mouth, the limited oxygen penetration in the sediment combined with important hydro-sedimentary processes constitute stressful conditions for foraminiferal faunas dominated by opportunistic species (e.g. Leptohalysis scottii). With increasing distance from the river mouth, foraminiferal faunas (e.g. Nonionella turgida, Eggerella scabra) adapted to thrive in sediments enriched in Rhône-derived organic matter under more stable hydro-sedimentary conditions appear. In the distal part of the Rhône River influence, benthic species (e.g. Valvulineria bradyana, Textularia agglutinans) living in fine sediment enriched in both continental and marine organic compounds emerge. At the deepest stations located in the south-eastern part of our study area, benthic foraminiferal faunas (e.g. Bulimina aculeata, Melonis barleeanus, Bigenerina nodosaria) are highly diverse, underlining stable environmental conditions characterised by marine-derived organic matter supplies and relatively deep oxygen penetration depth in the sediment. We also compare foraminiferal faunas sampled in September 2006 with communities sampled in June 2005, one month after the Rhône River annual flood (Mojtahid et al., 2009). This comparison suggests that opportunistic species (e.g. B. aculeata, Cassidulina carinata, V. bradyana) have responded to organic matter inputs related to marine primary production in June 2005.     

A numerical analysis of the three-dimensional rayleigh-benard convection spectra

The problem of the incompressible liquid convection between two horizontal planes heated on the underside is considered in the three-dimensional statement. The horizontal boundaries are assumed to be free of tangential stresses and isothermal. The calculated temporal spectrum of the temperature pulsations at the convection cell center at a supercriticality of 410 agrees well with the experimental measurement result. The Bolgiano-Obukhov (BO), k ^−11/5, k ⁻³, and k ⁻⁵, were obtain for the velocity pulsations. The Kolmogorov spectra k ^−5/3 and k ^−2.4 were obtained for the temperature pulsations. The presence of clearly identified spectra in the convective flow under study allows this process to be characterized as developed turbulence.     

A review of marine mammal,sea turtle and seabird bycatch in USA fisheries and the role of policy in shaping management

This paper reviews the available information (observer programs, estimates, statutes, regulations) for bycatch of marine mammals, sea turtles, and seabirds in fisheries of the United States. Goals of the review were to evaluate the state of knowledge of bycatch and the role of existing protective legislation in shaping bycatch management for different taxa. Pressing issues are identified, as well as knowledge gaps and policy limitations that hinder multi-species bycatch reduction. The USA has made important progress toward reducing bycatch in its fisheries, but the efficacy of its management has been limited somewhat by a focus on taxon- and fishery-specific regulation and the lack of consistent mandate across taxa for taking a cumulative perspective on bycatch. Applying consistent criteria across taxa for setting bycatch limits (e.g., extending the approach used for marine mammals to sea turtles and seabirds) would be the first step in a multi-species approach to bycatch reduction. A population-based multi-species multi-gear approach to bycatch would help identify priority areas where resources are needed most and can be used most effectively.     

A temporally second-order accurate Godunov-type scheme for solving the extended Boussinesq equations

A numerical scheme for solving the class of extended Boussinesq equations is presented. Unlike previous schemes, where the governing equations are integrated through time using a fourth-order method, a second-order Godunov-type scheme is used thus saving storage and computational resources. The spatial derivatives are discretised using a combination of finite-volume and finite-difference methods. A fourth-order MUSCL reconstruction technique is used to compute the values at the cell interfaces for use in the local Riemann problems, whilst the bed source and dispersion terms are discretised using centred finite-differences of up to fourth-order accuracy. Numerical results show that the class of extended Boussinesq equations can be accurately solved without the need for a fourth-order time discretisation, thus improving the computational speed of Boussinesq-type numerical models. The numerical scheme has been applied to model a number of standard test cases for the extended Boussinesq equations and comparisons made to physical wave flume experiments.     

Velocity potential formulations of highly accurate Boussinesq-type models

The highly accurate Boussinesq-type equations of Madsen et al. (Madsen, P.A., Bingham, H.B., Schäffer, H.A., 2003. Boussinesq-type formulations for fully nonlinear and extremely dispersive water waves: Derivation and analysis. Proc. R. Soc. Lond. A 459, 1075–1104; Madsen, P.A., Fuhrman, D.R., Wang, B., 2006. A Boussinesq-type method for fully nonlinear waves interacting with a rapidly varying bathymetry. Coast. Eng. 53, 487–504); Jamois et al. (Jamois, E., Fuhrman, D.R., Bingham, H.B., Molin, B., 2006. Wave-structure interactions and nonlinear wave processes on the weather side of reflective structures. Coast. Eng. 53, 929–945) are re-derived in a more general framework which establishes the correct relationship between the model in a velocity formulation and a velocity potential formulation. Although most work with this model has used the velocity formulation, the potential formulation is of interest because it reduces the computational effort by approximately a factor of two and facilitates a coupling to other potential flow solvers. A new shoaling enhancement operator is introduced to derive new models (in both formulations) with a velocity profile which is always consistent with the kinematic bottom boundary condition. The true behaviour of the velocity potential formulation with respect to linear shoaling is given for the first time, correcting errors made by Jamois et al. (Jamois, E., Fuhrman, D.R., Bingham, H.B., Molin, B., 2006. Wave-structure interactions and nonlinear wave processes on the weather side of reflective structures. Coast. Eng. 53, 929–945). An exact infinite series solution for the potential is obtained via a Taylor expansion about an arbitrary vertical position z = zˆ. For practical implementation however, the solution is expanded based on a slow variation of zˆ and terms are retained to first-order. With shoaling enhancement, the new models obtain a comparable accuracy in linear shoaling to the original velocity formulation. General consistency relations are also derived which are convenient for verifying that the differential operators satisfy a potential flow and/or conserve mass up to the order of truncation of the model. The performance of the new formulation is validated using computations of linear and nonlinear shoaling problems. The behaviour on a rapidly varying bathymetry is also checked using linear wave reflection from a shelf and Bragg scattering from an undulating bottom. Although the new models perform equally well for Bragg scattering they fail earlier than the existing model for reflection/transmission problems in very deep water.     

Thermodynamic characterization of boltwoodite and uranophane: Enthalpy of formation and aqueous solubility

Boltwoodite and uranophane are uranyl silicates common in oxidized zones of uranium ore deposits. An understanding of processes that impact uranium transport in the environment, especially pertaining to the distribution of uranium between solid phases and aqueous solutions, ultimately requires determination of thermodynamic parameters for such crystalline materials. We measured formation enthalpies of synthetic boltwoodites, K(UO₂)(HSiO₄)·H₂O and Na(UO₂)(HSiO₄)·H₂O, and uranophane, Ca(UO₂)₂(HSiO₄)₂·5H₂O, by high temperature oxide melt solution calorimetry. We also studied the aqueous solubility of these phases from both saturated and undersaturated conditions at a variety of pH. The combined data permit the determination of standard enthalpies, entropies and Gibbs free energies of formation for each phase and analysis of its potential geological impact from a thermodynamic point of view.     

Integrated Geological–Geophysical and Oceanographic Research in the South China Sea: Cruise 88 of the R/V “Akademik M.A. Lavrentyev”

Oceanology - Abstract—The paper gives brief results of comprehensive studies in the South China Sea obtained from a joint Russian–Vietnamese expedition in November 2019 (cruise 88 of...     

Vertical Variability of Primary Production and Chlorophyll a in the Kara Sea in the Middle of Summer: Contribution of Subsurface Maxima to the Water Column Values

Oceanology - Spatial and vertical variability of primary production (PP) and Chl a were studied in the framework of the 76th cruise of R/V Akademik Mstislav Keldysh to the Kara Sea from July 7 to...     

Modified Technique for Calculating the Parameters of Climatic Variability of Upwelling by Thermal Index

Izvestiya, Atmospheric and Oceanic Physics - A modified technique for calculating the amplitude-phase characteristics of the seasonal cycle and long-term trends in the intensity of upwelling is...