Beaver ponds boost mercury levels downstream

DeMarco, Emily

doi:10.1126/science.aad7391

Cited by 1 publication

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“…However, beaver ponds do have some negative effects as they could increase methylmercury (MeHg) in surface waterbodies (Roy et al 2009, DeMarco 2015, Levanoni et al 2015, Ecke et al 2017, Ortega et al 2018). For example, studies carried out in Canada (Roy et al 2009) and Sweden (Ortega et al 2018) reported that beaver impoundments create suitable conditions for MeHg formation because of low stream flow and thick sediment layer that is rich in the organic carbon.…”

Section: Discussionmentioning

confidence: 99%

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The effect of beaver dams on organic carbon, nutrients and methyl mercury distribution in impounded waterbodies

et al. 2020

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The European beaver Castor fiber is well‐known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016–2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid‐pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation.

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Section: Discussionmentioning

confidence: 99%

“…Furthermore, recent studies also show that beaver ponds can increase methylmercury (MeHg) concentrations within impounded waterbodies (DeMarco 2015, Levanoni et al 2015, Ortega et al 2018). In impounded waterbodies, methylation of Hg is favoured by absence of free oxygen and is mediated by bacteria species as Desulfovibrio desulfuricans and Geobacter sp.…”

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confidence: 99%