Recovery of polluted ecosystems: the case for long-term studies

Recovery of marine ecosystems from pollution has tended to receive less attention than the study of new or continuing impacts, but such studies are important in charting recovery from acute incidents and following legislation to deal with chronic contamination. Recovery is inevitably a long-term process, and where such studies have been made they are often too short-lived. Interest quickly wanes following an acute incident and governmental bodies rapidly switch to new legislative priorities for chronic inputs. We review three case studies: recovery of dogwhelk populations after local extinction by tributyl tin leachates from anti-fouling paints; recovery of rocky shore communities from oil spills; and recovery of estuarine ecosystems from industrial and urban development. We then make some generalisations about recovery processes before making a plea for long-term studies of polluted areas.     

Direct barite determination using SEM/EDS-ACC system: implication for constraining barium carriers and barite preservation in marine sediments

Barite (BaSO₄) in marine sediments is considered as a proxy of surface ocean productivity and is widely used for paleo-productivity reconstructions. However, direct barite determination is not achieved by currently used methods, which rely on the measurement of total barium by inductively coupled plasma–mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA) and correction from the allogenic Ba contribution. We report here on a technique that directly counts individual barite crystals using a scanning electron microscope (SEM) coupled to an energy dispersive spectrometer (EDS) equipped with an automated particle counting and classification (ACC) system. We show that barite–Ba concentrations can be deduced from the abundance, shape and size distributions of barite crystals with current precision and sensitivity as high as ±5 wt.% (2σ confidence limit) and 10 ppm, respectively. This technique, coupled with ICP-MS and INAA techniques for total Ba measurements, was applied to sediment samples from the tropical North Atlantic and the Central North Pacific oceans. Results show that: (1) barite and detrital aluminosilicates are the two main carriers of Ba in the investigated sediments; (2) calculated Ba/Al ratios range from 0.005 to 0.008 with an average value around 0.0066, in close agreement with previously reported values; (3) barite might not be the major source for released barium out of sediments and we suggest instead adsorbed barium as a potential source.     

Murky waters: Media reporting of marine protected areas in South Australia

Given the public's limited knowledge of marine environments, informing the public about marine protection presents a unique challenge. Studies have shown a well-informed public is more likely to support environmental issues and that newspapers, in particular, are considered a credible media source. This research investigates media representations of current South Australian efforts to establish a marine protected area (MPA). Articles from five newspapers between 1999 and 2006 were examined for content in the following areas: local marine ecology, the policy process of MPA establishment and stakeholder views. The research found that newspapers concentrated their reporting on opposing stakeholders, opinions and were largely ineffective in conveying the significance of the local marine ecology, the economic benefits of the MPA, and the delayed establishment process. These information gaps have left the public poorly informed, and therefore, there is unlikely to be significant pressure to overcome the continued delays in the establishment process.     

On the moisture-related buckling of marine composite panels using approximate analysis

A discussion is presented that highlights the growing utilization of composite structures for marine applications. Important to this trend is an understanding of the buckling response of marine panels under hygroscopic loads. Consideration are presented for the use of eigensensitivity analysis as a means of developing an approximate closed-form expression for computing the critical buckling response in the absense of an exact solutions     

Oxygen isotopes of phosphatic compounds—Application for marine particulate matter, sediments and soils

The phosphate oxygen isotopic composition in naturally occurring particulate phosphatic compounds (δ¹⁸O_p) can be used as a tracer for phosphate sources and to evaluate the cycling of phosphorus (P) in the environment. However, phosphatic compounds must be converted to silver phosphate prior to isotopic analysis, a process that involves digestion of particulate matter in acid. This digestion will hydrolyze some of the phosphatic compounds such that oxygen from the acid solution will be incorporated into the sample as these phosphatic compounds are converted to orthophosphate (PO₄³⁻). To determine the extent of incorporation of reagent oxygen into the sample, we digested various phosphatic compounds in both acid amended with H₂¹⁸O (spiked) and unspiked acid and then converted the samples to silver phosphate for δ¹⁸O_p analysis. Our results indicate that there is no isotopic fractionation associated with acid digestion at 50 °C. Furthermore, we found that reagent oxygen incorporation is a function of the oxygen to phosphorus ratio (O:P) of the digested compound whereby the percentage of reagent oxygen incorporated into the sample is the same as that which is required to convert all of the P-compounds into orthophosphate. Based on these results, we developed a correction for reagent oxygen incorporation using simple mass balance, a procedure that allows for the determination of the δ¹⁸O_p of samples containing a mixture of phosphatic compounds. We analyzed a variety of environmental samples for δ¹⁸O_p to demonstrate the utility of this approach for understanding sources and cycling of P.     

Vertical Variations of Core Sound Velocity: Evidence of Paleooceanographic History Since the Pleistocene Epoch

The vertical variations in the borehole core sound velocity (Cp) of the submarine sediments are related to the events of marine transgression and regression in the geologic history. This article establishes the vertical variation of Cp curve for the borehole sound velocity in the northern South China Sea continental shelf and the East China Sea continental shelf, thus providing evidence for revealing at least (3) sedimentary cycle events of marine transgression and regression occurring in the west Pacific marginal sea since the Pleistocene Epoch. The sound velocity of marine sediments brought in the course of marine transgression is lower (1450-1510 m/s) while that of continental sediments formed in the course of marine regression is higher (1650-1720 m/s).     

Renewable energy from the ocean

Growing concern over the threat of global climate change has led to an increased interest in research and development of renewable energy technologies. The ocean provides a vast source of potential energy resources, and as renewable energy technology develops, investment in ocean energy is likely to grow. Research in ocean thermal energy conversion, wave energy, tidal energy, and offshore wind energy has led to promising technologies and in some cases, commercial deployment. These sources have the potential to help alleviate the global climate change threat, but the ocean environment should be protected while these technologies are developed. Renewable energy sources from the ocean may be exploited without harming the marine environment if projects are sited and scaled appropriately and environmental guidelines are followed.     

Sensitivity of extreme hydroelastic load effects to changes in ship hull stiffness and structural damping

A new hybrid method for the time-domain nonlinear simulation of the hydroelastic load effects and the peak over threshold (POT) method for the calculation of the short-term extreme responses are briefly described and applied to a flexible SL-7 class containership and a flexible liquefied natural gas (LNG) ship. Three stiffness levels, three stiffness distributions and three modal damping ratios are used to study the influence of the hull flexibility and structural damping on the short-term prediction of extreme vertical hydroelastic load effects. The results give justification for some simplified treatment of the first vertical flexible mode in early design stage when structural details are not available.