Mercury methylation rates in Deception Island (Maritime Antarctica) waters and pyroclastic gravel impacted by volcanic mercury.

Deception Island is an active volcano in the Antarctica being volcanism a source of mercury. To improve the understanding of the Hg cycle in this remote ecosystem, pyroclastic gravel and water samples were collected and total (THg) and monomethylmercury (MMHg) concentrations were measured as well as the potential for Hg methylation. Gravel samples collected close to active fumaroles showed the highest THg levels (72 ng/g) while in water samples the highest concentrations of THg (1.2 ng/L) and MMHg (0.45 ng/L) where found. Methylation activity was barely observable in gravel samples. Biotic methylation rates in water were up to 13 times higher compared to those recorded previously in other polar waters. Abiotic methylation processes also play an important role, with up to 0.54 ± 0.43% of added Hg converted instantaneously to MMHg. These results suggest that Deception Island presents favourable conditions for MMHg explaining the elevated concentrations of both THg and MMHg in this ecosystem.

Evaluating trace element bioavailability and potential transfer into marine food chains using immobilised diatom model species Phaeodactylum tricornutum, on King George Island, Antarctica.

In order to evaluate trace element bioavailability and potential transfer into marine food chains in human impacted areas of the Fildes Peninsula (King George Island, South Shetland Islands Archipelago), element levels (Cr, Ni, Cu, Zn, Cd, and Pb) were determined in water, sediments, phytoplankton, and in diatom Phaeodactylum tricornutum Bohlin (Bacillariophyceae) cells immobilised in alginate and exposed to water and sediments, from the Bellingshausen Dome (reference site) and Ardley Cove (human impacted area), during January 2014. High element concentrations in exposed P. tricornutum indicated element mobilisation from sediments into the water. Levels in exposed cells reflected the sediment element content pattern, comparable to those found in phytoplankton, supporting phytoplankton as an important path of trace element entry into marine food chains. This study clearly shows immobilised P. tricornutum as good proxy of phytoplankton concerning element accumulation efficiency, and an effective tool to monitor trace element contamination in polar coastal ecosystems.