Origins and discrimination between local and regional atmospheric pollution in Haiphong (Vietnam), based on metal(loid) concentrations and lead isotopic ratios in PM10.

Southeast Asia is a hotspot of anthropogenic emissions where episodes of recurrent and prolonged atmospheric pollution can lead to the formation of large haze events, giving rise to wide plumes which spread over adjacent oceans and neighbouring countries. Trace metal concentrations and Pb isotopic ratios in atmospheric particulate matter < 10 µm (PM10) were used to track the origins and the transport pathways of atmospheric pollutants. This approach was used for fortnightly PM10 collections over a complete annual cycle in Haiphong, northern Vietnam. Distinct seasonal patterns were observed for the trace metal concentration in PM10, with a maximum during the Northeast (NE) monsoon and a minimum during the Southeast (SE) monsoon. Some elements (As, Cd, Mn) were found in excess according to the World Health Organization guidelines. Coal combustion was highlighted with enrichment factors of As, Cd, Se, and Sb, but these inputs were outdistanced by other anthropogenic activities. V/Ni and Cu/Sb ratios were found to be markers of oil combustion, while Pb/Cd and Zn/Pb ratios were found to be markers of industrial activities. Pb isotopic composition in PM10 revealed an important contribution of soil dusts (45-60%). In PM10, the Pb fraction due to oil combustion was correlated with dominant airflow pathways (31% during the north-easterlies and 20% during the south-easterlies), and the Pb fraction resulting from industrial emissions was stable (around 28%) throughout the year. During the SE monsoon, Pb inputs were mainly attributed to resuspension of local soil dusts (about 90%), and during the NE monsoon, the increase of Pb inPM10 was due to the mixing of local and regional inputs.

Coral Mucus Is a Hot Spot for Viral Infections.

There is increasing suspicion that viral communities play a pivotal role in maintaining coral health, yet their main ecological traits still remain poorly characterized. In this study, we examined the seasonal distribution and reproduction pathways of viruses inhabiting the mucus of the scleractinians Fungia repanda and Acropora formosa collected in Nha Trang Bay (Vietnam) during an 11-month survey. The strong coupling between epibiotic viral and bacterial abundance suggested that phages are dominant among coral-associated viral communities. Mucosal viruses also exhibited significant differences in their main features between the two coral species and were also remarkably contrasted with their planktonic counterparts. For example, their abundance (inferred from epifluorescence counts), lytic production rates (KCN incubations), and the proportion of lysogenic cells (mitomycin C inductions) were, respectively, 2.6-, 9.5-, and 2.2-fold higher in mucus than in the surrounding water. Both lytic and lysogenic indicators were tightly coupled with temperature and salinity, suggesting that the life strategy of viral epibionts is strongly dependent upon environmental circumstances. Finally, our results suggest that coral mucus may represent a highly favorable habitat for viral proliferation, promoting the development of both temperate and virulent phages. Here, we discuss how such an optimized viral arsenal could be crucial for coral viability by presumably forging complex links with both symbiotic and adjacent nonsymbiotic microorganisms.

Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas).

This study evaluated embryotoxicity and genotoxicity of two dissolved metals copper and cadmium (Cu and Cd) and two pesticides (metolachlor and irgarol) occurring in Arcachon Bay (SW France) in Pacific oyster (Crassostrea gigas) larvae and investigated the relationship between those two endpoints. Embryotoxicity was measured by calculating the percentage of abnormal D-shaped larvae and genotoxicity was evaluated with DNA strand breaks using the comet assay. After 24h exposure, significant increases of the percentage of abnormal D-larvae and the DNA strand breaks were observed from 0.1 µg L⁻¹ for Cu, 10 µg L⁻¹ for Cd and 0.01 µg L⁻¹ for both irgarol and metolachlor in comparison with the controls. A strong positive relationship between embryotoxicity and genotoxicity was recorded for Cu, Cd and metolachlor. The current study suggests that copper, irgarol and metolachlor can induce larval abnormalities and DNA damage in a population of exposed oysters at environmentally relevant concentrations.