Transfer of elements released by aluminum galvanic anodes in a marine sedimentary compartment after long-term monitoring in harbor and laboratory environments.

Cathodic protection by galvanic anodes (GACP) is often used to protect immerged metallic structures in harbor environments, especially GACP employing aluminum-based anodes. To follow a previous study that was performed in a laboratory on Al-anode, two monitoring periods were performed in parallel, one in an in situ environment (in the Port of Calais) for 42 months and the other in a laboratory for 18 months, to evaluate the transfer of metals constituting the Al-anode towards the sedimentary compartment. During each monitoring, two conditions of agitation of water (weak and strong) were compared, and different factors of sediment quality were used to assess the enrichment and potential toxic effects of these released metals. The results showed that the dissolution of Al-anode-induced a greater Zn enrichment of sediment than an Al enrichment. This is in contrast with the abundance of these elements present in the composition of the anode and suggested a potential toxic effect for marine organisms with regards to the discovered Zn level, especially in confined areas.

Meiofauna distribution in a mangrove forest exposed to shrimp farm effluents (New Caledonia).

Meiofauna abundance, biomass and individual size were studied in mangrove sediments subjected to shrimp farm effluents in New Caledonia. Two strategies were developed: i) meiofauna examination during the active (AP) and the non-active (NAP) periods of the farm in five mangrove stands characteristics of the mangrove zonation along this coastline, ii) meiofauna examination every two months during one year in the stand the closest to the pond (i.e. Avicennia marina). Thirteen taxonomic groups of meiofauna were identified, with nematodes and copepods being the most abundant ones. Meiofauna abundance and biomass increased from the land side to the sea side of the mangrove probably as a result of the increased length of tidal immersion. Abundance of total meiofauna was not significantly different before and after the rearing period. However, the effluent-receiving mangrove presented twice the meiofauna abundance and biomass than the control one. Among rare taxa, mites appeared extremely sensitive to this perturbation.