Methyl halide production and loss rates in sea water from field incubation experiments

Experiments were conducted in the field to determine the non-chemical loss rate of methyl iodide in seawater and to examine production rates of methyl halides. The loss rate of added C13 labelled methyl iodide, present at concentrations similar to those found in seawater, corrected for chemical loss due to reaction with Cl⁻ varied from < 1 to 18% day^− 1, with a mean value of 7%. This rate of loss is much lower than that which was proposed by Bell et al. [Bell, N., Hsu, L., Jacob, D. J., Schultz, M. G., Blake, D. R., Butler, J. H., King, D. B., Lobert, J. M., Maier-Reimer, E., 2002. Methyl iodide: Atmospheric budget and use as a tracer of marine convection in global models, Journal of Geophysical Research-Atmospheres 107(D17), 4340-4351.] to account for the large discrepancies between observed and predicted mid-latitude concentrations of CH₃I based on their global photochemical source model. The suitability of several types of container for seawater incubations was studied and only quartz tubes appeared to be free of experimental artifact. Collapsible polyvinyl fluoride containers showed major production of methyl halides on irradiation with simulated sunlight. Polyethylene containers caused spurious production of methyl iodide at lower rates.     

Feature modeling approach to simulating Loop Current Frontal Eddies

Loop Current Frontal Eddies (LCFE) in the Gulf of Mexico are simulated with a regional configuration of the Princeton Ocean Model using a feature-oriented initialization technique. The initialization procedure is based on a prior investigation of stability characteristics of the Loop Current (LC). Zonal channel experiments conducted with a multi-layer intermediate equations model allowed to identify conditions necessary for formation and growth of frontal eddies. The simulations were able to reproduce key features of LCFE-topography interaction in the DeSoto Canyon region observed during the “Eddy Intrusion” study.     

Mussels document loss of bioavailable polycyclic aromatic hydrocarbons and the return to baseline conditions for oiled shorelines in Prince William Sound, Alaska

Polycyclic aromatic hydrocarbons (PAH) were measured in mussels (Mytilus trossulus) collected between 1990 and 2002 from 11 sites on the shores of Prince William Sound (PWS), Alaska, that were heavily oiled by the 1989 Exxon Valdez oil spill (EVOS). This study, utilizing the methods of the NOAA Status and Trends Mussel Watch Program, found that concentrations of PAH released from spill remnants have decreased dramatically with time and by 2002 were at or near the range of total PAH (TPAH) of 3-355 ng/g dry weight obtained for mussels from unoiled reference sites in PWS. Time-series TPAH data indicate a mean TPAH half-life in mussel tissues of 2.4 years with a range from 1.4 to 5.3, yielding an annual mean loss of bioaccumulated TPAH of 25%. The petroleum-derived TPAH fraction in mussel tissues has decreased with time, reflecting the decreasing release of EVOS residues in shoreline sediments. These results show that PAH from EVOS residues that remain buried in shoreline sediments after the early 1990s are in a form and at locations that have a low accessibility to mussels living in the intertidal zone.     

A numerical experiment on the calculation of the tropical Atlantic circulation in 1982–1983, with the real wind considered

This paper discusses the results obtained through numerical modelling of the annual course of circulation and thermohaline field evolution in the tropical Atlantic under the impact of real wind forcing (from March 1982 to March 1983) and compares them with the calculation of seasonal variability induced by the climatic wind. Changes in the pattern of the equatorial currents and related temperature fields induced by the specific peculiarities in the wind field are analysed.Translated by Vladimir A. Puchkin.     

Accommodating ecotourism in multiple use planning of coastal and marine protected areas

Coastal and marine areas the world over provide food, transportation, recreation, and energy resources to increasing numbers of people each year. As demands for these resources rise, the potential for user conflicts is radically heightened. This situation can be avoided or counteracted by instigating proactive multiple use planning. Multiple use zoning plans can only exist in a concrete management framework: marine and coastal protected areas provide just such a foundation. Nature-based or ecotourism can be encouraged in coastal protected areas aimed at achieving sustainability. Well-planned tourism provides economic and political incentives for management and for conservation, and may bring additional benefits to local communities and regional economies. Examples where nature-based tourism has been or is becoming successfully integrated into multiple use planning can be found in Quintana Roo, Mexico; the Lesser Antilles; and Australia, among other areas.     

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.     

Comparative toxicities of chlorinated biphenyls on sea urchin egg fertilisation and embryogenesis

The aim of this study was to compare the biological actions of selected chlorinated biphenyls (CB's) (with different degrees of chlorine substitution), using the sea urchin test system, for their ability to affect fertilisation, embryogenesis and mitotic activity. Sea urchin embryos were exposed to the test agents throughout larval development or for shorter intervals (e.g. before or after hatching). Sperm or eggs were exposed before fertilisation, thereafter the contaminants were removed from embryo cultures. The results showed maximal activities from medium-chlorinated (tetra- and hexachloro-substituted) compounds, as compared to low- and high-chlorinated biphenyls (mono-, di- and octachloro-substituted), at nominal levels ranging from 10⁻⁶m to 10⁻⁵m. This held true for the different parameters and treatment schedules. Developmental defects were only detected following post hatching exposure of embryos to CB's, whereas pre-hatching exposure failed to reveal any embryological or cytogenetic abnormalities.     

The influence of dissolved petroleum hydrocarbon residues on natural phytoplankton biomass

The effect of dissolved petroleum hydrocarbons in the environment on phytoplankton biomass measured as chlorophyll a was studied near the oil tanker route in the southern Bay of Bengal. In the transect from 5° N, 77° E to 5° N, 87° E the concentrations of dissolved petroleum hydrocarbons were negatively correlated with phytoplankton biomass, whereas in the 0° N, 87° E to 1° N, 79° E transect they were positively correlated with phytoplankton biomass. The mean petroleum hydrocarbon concentrations in the two transects were 12·12 ± 4·67 μg litre⁻¹ and 11·23 ± 4·5 μg litre⁻¹, respectively.It is surmised that the effect of dissolved petroleum hydrocarbons on phytoplankton biomass varies depending on the nature rather than the quantity of petroleum hydrocarbons present. Culture studies with unialgal Nitzschia sp. in seawater collected from selected stations in the study area as well as in artificial seawater spiked with the water-soluble petroleum hydrocarbon fraction of light Arabian Crude support this.     

Study of fluoride in polluted and unpolluted estuarine environments

Mindhola River estuary, which receives industrial waste containing high concentrations of fluoride, and Purna River estuary, which is free from fluoride contamination, have been investigated. While fluoride behaved conservatively in Purna River estuary, significant deviation from the theoretical dilution line (TDL) in the chlorinity range 0·5–8‰ was observed in Mindhola River estuary due to the externally added fluoride which largely remained in solution. The excess of fluroide over the theoretically calculated value was at a maximum around a chlorinity of 3‰. High natural fluoride content of the river waters resulted in F/Cl ratios exceeding 300 × 10⁻⁵ at low chlorinities. The ratio decreased rapidly with increasing chlorinity and the value near to that of seawater was observed at chlorinities above 14‰.     

Geoacoustic and physical properties of carbonate sediments of the Lower Florida Keys

 Near-surface sediment geoacoustic and physical properties were measured from a variety of unconsolidated carbonate sediments in the Lower Florida Keys. Surficial values of compressional and shear speed correlate with sediment physical properties and near-surface acoustic reflectivity. Highest speeds (shear 125–150 m s^-1; compressional 1670–1725 m s^-1) are from sandy sediments near Rebecca Shoal and lowest speeds (shear 40–65 m s^-1; compressional 1520–1570 m s^-1) are found in soft, silty sediments which collect in sediment ponds in the Southeast Channel of the Dry Tortugas. High compressional wave attenuation is attributed to scattering of acoustic waves from heterogeneity caused by accumulation of abundant shell material and other impedance discontinuities rather than high intrinsic attenuation. Compared to siliciclastic sediments, carbonate sediment shear wave speed is high for comparable values of sediment physical properties. Sediment fabric, rather than changes due to the effects of biogeochemical processes, is responsible for these differences.