Most crude oils spread on open water to an average thickness as low as 0.1mm. The application of dispersants enhances the transport of oil as small droplets into the water column, and when combined with the turbulence of 1m waves will quickly entrain oil into the top 1m of the water column, where it rapidly dilutes to concentrations less than 100ppm. In less than 24h, the dispersed oil is expected to mix into the top 10m of the water column and be diluted to concentrations well below 10ppm, with dilution continuing as time proceeds. Over the multiple weeks that biodegradation takes place, dispersed oil concentrations are expected to be below 1ppm. Measurements from spills and wave basin studies support these calculations. Published laboratory studies focused on the quantification of contaminant biodegradation rates have used concentrations orders of magnitude greater than this, as it was necessary to ensure the concentrations of hydrocarbons and other chemicals were higher than the detection limits of chemical analysis. However, current analytical methods can quantify individual alkanes and PAHs (and their alkyl homologues) at ppb and ppm levels. To simulate marine biodegradation of dispersed oil at dilute concentrations commonly encountered in the field, laboratory studies should be conducted at similarly low hydrocarbon concentrations.

The quantification of entanglements of megafauna with plastic debris at sea is difficult to assess for several reasons, such as detection and reporting biases. We used standardized vessel based counts to describe and quantify the occurrence of marine debris entanglements in northern gannets Morus bassanus at five of its main wintering areas. We observed 34 entangled birds in total, representing 0.93% of all gannets counted (n=3672 individuals). The incidence of entanglements largely varied geographically, being exceptionally high off Mauritania (20.2% of the birds in late spring). Most birds affected were immature (1.88% compared to 0.06% in adults), which in turn represented 52.4% of all the birds. Entanglements in the lower bill mandible were the most frequent, mainly with red-colored plastic objects. Further research is urgently needed to evaluate the impact of entanglements at the population level and its occurrence in other marine species, and to seek potential solutions.

The ocean has been shielding the earth from the worst effects of rapid climate change by absorbing excess carbon dioxide from the atmosphere. This absorption of CO2 is driving the ocean along the pH gradient towards more acidic conditions. At the same time ocean warming is having pronounced impacts on the composition, structure and functions of marine ecosystems. Warming, freshening (in some areas) and associated stratification are driving a trend in ocean deoxygenation, which is being enhanced in parts of the coastal zone by upwelling of hypoxic deep water. The combined impact of warming, acidification and deoxygenation are already having a dramatic effect on the flora and fauna of the oceans with significant changes in distribution of populations, and decline of sensitive species. In many cases, the impacts of warming, acidification and deoxygenation are increased by the effects of other human impacts, such as pollution, eutrophication and overfishing.The interactive effects of this deadly trio mirrors similar events in the Earth’s past, which were often coupled with extinctions of major species’ groups. Here we review the observed impacts and, using past episodes in the Earth’s history, set out what the future may hold if carbon emissions and climate change are not significantly reduced with more or less immediate effect.

This study aimed to compare the contamination levels of various organohalogenated compounds in two migratory fish species in the Vilaine River in western France. Organochlorinated pesticides, polychlorinated biphenyls (PCBs), dioxins (polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs)), and polybrominated diphenyl ethers (PBDEs) were analyzed in two diadromous species from the Vilaine estuary, the grey mullet (Liza ramada)-an amphihaline species, and the allis shad (Alosa alosa)-an anadromous species. Fish were collected in spring 2004 and spring 2005, upstream and downstream of the Arzal Dam. PCB contamination varied from 27 to 200 ng g(-1) dry weight (d.w.). PCDDs/Fs, expressed in toxicity equivalent quantity (TEQ) varied from 0.4 to 2.8 pg g(-1) d.w. Dioxins and dioxin-like PCBs expressed in total TEQ varied from 1.4 to 18.8 pg g(-1) d.w. PBDE47 was present at around 2-10 ng g(-1) d.w. and concentrations of the insecticide dichlorodiphenyltrichloroethane breakdown product p,p'-dichlorodiphenylchloroethylene varied from 1 to 14 ng g(-1) d.w. For both species, specimens collected upstream were more contaminated. The grey mullet specimens were less contaminated than the allis shad when taken downstream of the dam but were more contaminated upstream. The allis shads presented intermediate contaminant concentrations with a less pronounced difference between upstream and downstream specimens. However, it is thought that shads do not feed when they spawn in the upstream parts of rivers, which should modify the contaminant concentrations. However, measurements in upstream shad samples show an unexpected increase of the contamination, which remains unexplained.

A multibiomarker approach was developed on juvenile Atlantic tomcod (Microgadus tomcod) to evaluate the pertinence of this approach for low-cost screening assessment of the environmental quality of various coastal sites within estuaries. Several biometric indices and biomarkers (ethoxyresorufin-O-deethylase (EROD) activity, metallothionein concentration, and immune responses) were investigated on immature and maturing tomcods (a parts per thousand currency sign31 months) collected in four environmentally contrasted sites in the St. Lawrence Estuary (SLE). Simultaneous examination of various age classes provides the opportunity to detect short-term responses in sensitive young-of-the-year fish (e.g., EROD induction) and longer-time effects associated with chronic exposure and bioaccumulation (e.g., metallothionein induction). Principal component analysis was helpful to discriminate between responses possibly related to contaminant exposure (EROD, metallothionein) and responses that could be affected by upstream-downstream gradient (immune response, biometric indices). Measurement of a battery of biomarkers in young tomcods at several sites along the shore of the SLE is a low-cost screening investigation useful to identify hot spots requiring further investigation with chemical analysis and additional reference sites.

Global marine vessels emissions are adversely affecting human health particularly in southeast Asia. But health burdens from both ocean- and river-going vessels in Pearl River Delta (PRD) regions are not quantified. We estimated the potential health impacts using pooled relative risks of mortality and hospital admissions in China, and the model derived concentrations of sulfur dioxide (SO2), particulate matter (PM10), nitrogen dioxide (NO2) and ozone (O3) due to vessels emissions. SO2 concentrations due to marine emissions in Hong Kong were 13.6μgm−3 compared with 0.7μgm−3 in PRD regions that were far from the marine vessels. In PRD regions, the estimated annual numbers (per million people) of excess deaths from all natural causes and hospital admissions from cardiorespiratory causes attributable to SO2, NO2, O3 and PM10 combined from marine emissions were 45 and 265 respectively. Marine emission control measures could contribute a large reduction in mortality and hospital admissions in PRD regions especially in Hong Kong.

This study reveals potential accumulation of trace metals in the sea and groundwater due to ship breaking activities which take place along the Bay of Bengal in Sitakund Upazilla, Chittagong, Bangladesh. When compared with WHO and Bangladesh domestic standards for water quality, it is revealed that seawater was strongly polluted by Fe and Hg, moderately by Mn and Al, and slightly by Pb and Cd. Groundwater was strongly polluted by Fe, Pb and Hg, moderately by Mn and Al, and slightly by As. Trace element concentrations of all seawater samples exceeded the average concentration of elements in the Earth’s seawater. The application of Principal Components Analysis identified two sources of pollution–marine and ship breaking. The mechanism of groundwater pollution inferred that if seawater is polluted, nearby groundwater is also polluted with trace metals due to the influence of seawater intrusion.

Plastic marine debris is presently widely recognised as an important environmental pollutant. Such debris is reported in every habitat of the oceans, from urban tourist beaches to remote islands and from the ocean surface to submarine canyons, and is found buried and deposited on sandy and cobble beaches. Plastic marine debris varies from micrometres to several metres in length and is potentially ingested by animals of every level of the marine food web. Here, we show that synthetic polymers are present in subsurface plankton samples around Saint Peter and Saint Paul Archipelago in the Equatorial Atlantic Ocean. To explain the distribution of microplastics around the Archipelago, we proposed a generalised linear model (GLM) that suggests the existence of an outward gradient of mean plastic-particle densities. Plastic items can be autochthonous or transported over large oceanic distances. One probable source is the small but persistent fishing fleet using the area.

We examined persistent organic pollutant and trace element concentrations in eggs of magnificent frigatebirds (Fregata magnificens), a species of conservation concern breeding in the West Indies. Despite that frigatebirds feed at high positions in tropical marine food chains, we detected low levels of most contaminants, suggesting limited contamination of their prey.