Transfer of marine mercury to mountain lakes

Abstract

Stocking 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 δ202Hg and higher Δ199Hg. 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.

Determinants of mercury contamination in viperine snakes, Natrix maura, in Western Europe

“…The relatively higher value of Hg concentrations and Hg accumulation rates in this population dovetail remarkably well with processes that have recently been described in highaltitude aquatic ecosystems (Hansson et al, 2017). In this study system, farmed trout raised on commercial pellets based on proteins from fishery products of marine origin show both high Hg concentrations and Hg isotopic signatures that are comparable to that of top-predator marine biota (Hansson et al, 2017). It is likely that the commercial pellets used to raise trouts at the Fontenille fish farm are also based on proteins from fishery products of marine origin, and that introduction of marine Hg through the fish food is responsible for the higher value of Hg concentrations and Hg accumulation rates in this N. maura population.…”

“…This study site is situated on a fish farm, and N. maura from this population feed heavily on the fry and juveniles trouts raised by the fish farm. The relatively higher value of Hg concentrations and Hg accumulation rates in this population dovetail remarkably well with processes that have recently been described in highaltitude aquatic ecosystems (Hansson et al, 2017). In this study system, farmed trout raised on commercial pellets based on proteins from fishery products of marine origin show both high Hg concentrations and Hg isotopic signatures that are comparable to that of top-predator marine biota (Hansson et al, 2017).…”

“…Interestingly, both Hg concentrations and Hg accumulation rate of the Fontenille population are even higher than the Ons population which feed on marine fish (Galân, 2012). Future studies should usefully assess the relative contribution of fish farming on Hg contamination in aquatic ecosystems and its role as a vector of Hg of marine origin in inland freshwater systems (Hansson et al, 2017).…”

Trace Element Concentrations in European Pond Turtles (Emys orbicularis) from Brenne Natural Park, France

“…Alternatively, relatively high concentrations of both Hg and Zn could be linked to the composition of fish pellets used for fish farming that occur in many ponds of Brenne. Indeed, commercial fish pellets exhibit high Hg concentrations of marine origin (Hansson et al 2017; see also Lemaire et al 2018) and are enriched with Zn oxide (EFSA 2012). Future studies should usefully investigate both the origin of Hg and Zn as well as the physiological and toxicological consequences of elevated levels of these elements for E. orbicularis (Meyer et al 2014).…”

Environmental causes and reproductive correlates of mercury contamination in European pond turtles (Emys orbicularis)

“…Cryptic sources can further complicate our understanding of the extent of Hg contamination. For instance, it has recently been shown that fish farming is responsible for the transfer of marine Hg to areas that superficially appear unaffected from other sources of pollution (Hansson et al 2017; see also Lemaire et al 2018;Guillot et al 2018).…”