Transfer of marine mercury to mountain lakes

International audienceStocking is a worldwide activity on geographical and historical scales. The rate of non-native fish introductions have more than doubled over the last decades yet the effect on natural ecosystems, in the scope of biologically mediated transport and biomagnification of Hg and Hg-isotopes, is unknown. Using geochemistry (THg) and stable isotopes (N, Sr and Hg), we evaluate natal origin and trophic position of brown trout (Salmo trutta fario), as well as mercury biomagnification trends and potential pollution sources to three high-altitude lakes. Farmed trout show Hg-isotope signatures similar to marine biota whereas wild trout shows Hg-isotope signatures typical of fresh water lakes. Stocked trout initially show Hg-isotope signatures similar to marine biota. As the stocked trout age and shifts diet to a higher trophic level, THg concentrations increase and the marine Hg isotope signatures, induced via farm fish feed, shift to locally produced MeHg with lower δ 202 Hg and higher Δ 199 Hg. We conclude that stocking acts a humanly induced biovector that transfers marine Hg to freshwater ecosystems, which is seen in the Hg-isotopic signature up to five years after stocking events occurred. This points to the need of further investigations of the role of stocking in MeHg exposure to freshwater ecosystems

Insecticide Resistance

Insecticides, including contact chemicals and fumigants, are essential components of the majority of stored product protection systems. Their use enables the implementation of effective quarantine systems, ensures food security and facilitates domestic and international trade. Insecticides have many advantages. They can be integrated easily into grain handling logistics; they reliably provide the freedom from insect infestation demanded by many markets; and they are relatively inexpensive to apply. Despite their central importance, however, there are a surprisingly small number of chemicals used in the protection of stored products. Chemical residue levels are tightly regulated as stored products are usually foods. In addition, because of the often large volumes of commodity involved and convenience of application, fumigants are frequently the preferred treatments, rather than liquid insecticides. However, fumigant use requires strict workplace health and safety precautions and must comply with stringent environmental constraints. These factors, coupled with toxicological considerations, limit the range of materials available for application to grain and make them costly to develop. For these reasons, loss of any one chemical treatment will have a significant impact on pest management. Consequently, the development of resistance in stored product pests to any registered insecticide is a particularly significant problem that requires urgent solutions