Newly inundated forest landscapes as hotspots for mercury bioaccumulation and transfer across the aquatic-terrestrial food web (INFORM-Hg)

Forest soils have retained high loads of anthropogenic mercury (Hg) since the start of the industrial era.

Inundation of forests, that flood terrestrial soils, can mobilize legacy Hg and promote the transformation of inorganic Hg to its bioaccumulative form methyl-Hg (MeHg). MeHg can bioaccumulate and biomagnify in the food-chain, and result in toxic levels in top-predators.

In this project we will study the role of newly created human- and beaver-induced wetlands for MeHg formation and Hg transfer across aquatic-terrestrial food webs, up to bats.Restoring formerly drained peatlands is encouraged from a political level to e.g. reduce flooding and droughts. An increasing number of inundations in the forest landscape are also created by an increasing beaver population.

This project, will test to which extent restored wetlands and beaver ponds cause higher Hg accumulation in biota compared to natural wetlands.

As new inundations may not only increase MeHg formation, but also alter the food-web structure, we will evaluate how food-web dynamics influence the biomagnification of Hg across the food chain. Finally, we will identify key site-specific characteristics that constitute a risk for elevated Hg in biota.

These objectives will be addressed by analyzing Hg (and MeHg), fatty acids and stable isotopes in biota over the food chain of; Algae/biofilms → aquatic insects → terrestrial predators (bats), in 20 restored wetlands, 20 beaver dams and 20 natural wetlands.