Mercury (Hg) contamination is a global issue due to its ability to undergo long-range transport and its
potential toxicity. Methylmercury (MeHg) is the toxic form of mercury that can be transferred in increasing
concentrations from prey to predator through aquatic food webs (biomagnification) resulting in Hg
concentrations in apex species that can be millions of times higher than those observed in the environment.
Ecosystem and food web characteristics influence Hg biomagnification: low productivity, acidic pH, cold
temperatures and the source of organic matter can indirectly increase Hg biomagnification by reducing
feeding and growth efficiency and lowering excretion rates of MeHg in biota, consequently increasing Hg
concentrations in top predators. However, the magnitude of influence of these variables on Hg
biomagnification in food webs are still unclear. It is also logical to think that physical-chemical properties and
therefore Hg levels of a given water body in a watershed might be influenced by the characteristics of the
streams, rivers and lakes and even the land cover that form that watershed. This reflects the high affinity of
Hg species to suspended particles and organic matter, and its modulation by pH and temperature and other
factors, which commonly vary between each of these components in a given watershed. However, there is
still confusion and disagreement regarding the importance of river/lake-landscape interactions
for total Hg inputs to freshwater systems at high latitudes, especially in the Southern Hemisphere.
These discussions have led our research team to two main hypothesis related to biogeochemical aspects of
flux, fate and distribution of mercury in pristine austral freshwater ecosystems, proposing that “A higher
wetland area ratio (compared to forest cover) within the catchment will contribute to mercury
bioavailability to Sub Antarctic aquatic systems in Chile.” and that “A steeper slope of the drainage
basin will increase the quantity of allochthonous (terrestrial) organic matter, increasing the pH,
and decreasing the bioavailability/biomagnification of mercury in the aquatic trophic web in
austral ecosystems in Chile”.
To achieve this, we set the following objectives:
• To assess natural Hg dynamics and the influence of catchments characteristics between river and lake
ecosystems in a remote area, free from industrial influences in the understudied southern hemisphere.
• To spatially and seasonally characterize the catchments landscapes and assess how
autochthonous(terrestrial)/allochthonous(aquatic) productivity affects mercury bioavailability and
accumulation processes within rivers/lakes from extreme austral basins.
Our research plan revolves around 4 field work campaigns conducted across 2 summers and 2 winterspring seasons in 5 sites among 3 basins in Tierra del Fuego, where human activities are minor or nonexistent. We will assess mercury (methyl and total mercury) levels in different trophic levels of the aquatic
food web, in surface water, sediments, riparian soil, and vegetation, along with analysis of stable isotopes
of N, C and S to model the flow of energy, organic matter and Hg through the system. Water chemistry,
micro and macronutrients, and landscape characteristics (measured by Unmanned Aerial Vehicles, to a
spatial resolution of 5 cm) will be analyzed and mapped along the pollutant and stable isotope data. The
proposal has several workshops at local and national level planned to highlight the importance of possible
landscape modification at catchment scale in Hg pollution. It also includes work within the Minamata
Convention implementation protocol within the Environment-based decision-making process Ministry for a
science. Our proposal will strengthen Hg studies in Chile and in Latin America and provide representative
benchmarks for much of the non-tropical southern hemisphere and for the globe. Chile is an ideal
location to undertake this work, as it includes a wide representation of different habitats and
ecological processes. Furthermore, it has many natural sources of Hg where we can assess
seasonal Hg flux, fate and effects on natural habitats and taxa without marked human
influences.