LAUSR

The 2015 Gold King Mine (GKM) spill into the Animas River, Colorado, USA, is an opportunity to evaluate acute mine discharge into a chronically metal-rich system. We measured metals, C and N isotopes in soil, water, sediment, plants, periphyton, invertebrates and fish to determine metal cycling between trophic levels in areas affected by the spill and chronic mine drainage from the Bonita Peak mining district during the past ~100 years. Soil and sediment metal levels were higher in sampling sites downstream of the mining district compared to a reference site without similar upstream mining activity. Plants at spill- and-mine-affected sites had higher metal concentrations: Pb in willow, Cd in cottonwood leaves, and Zn in all vegetation. Periphyton from spill-affected sites had higher concentrations of Fe, Zn, Cd and Pb than the reference site. Aquatic invertebrates in spill-affected areas had higher concentrations of metals compared with the reference that varied temporally. Diet reconstruction via δ 15 N and δ 13 C was most parsimonious for flannelmouth and blue suckers, but these fish did not show elevated metal levels in the spill-affected sites. Brown trout showed higher liver Zn, As and Cd in the spill-affected sites. In spite of mine drainage treatment implemented in response to the GKM spill, which has nearly eliminated dissolved metals leaving the Bonita Peak mining district, downstream GKM areas still exhibit higher metal levels across ecosystem components three-years following the spill; our results suggest that internal cycling via plant uptake, detritus-consuming aquatic invertebrates and bottom-feeding fish contribute to metal persistence in this area.