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Abstract Title: Mercury in Freshwater Ecosystems Along a Latitudinal Gradient along Chile
Presenter Name: Paulina Bahamonde
Company/Institution: Laboratory of Aquatic Environmental Research, Centro de Estudios Avanzados - HUB Ambiental UPLA, Universidad de Playa Ancha, Valpara¡so, Chile
Session: Special Session - Mercury in the Southern Hemisphere
Day and Session: Wednesday 27th July - Session One
Start Time: 06:30 UTC
Co-Authors: Paulina Bahamonde,Elvira Vergara

Abstract Information :

Chile extends across many degrees of latitude, including a large variety of biomes, and associated land use and industries. Northern Chile is dominated by desert and mining. Central Chile has a Mediterranean climate supporting agriculture and large urban areas. Southern Chile is subantarctic with little industrial activity. Rivers in central-northern Chile have been historically exposed to mercury pollution from a range of anthropogenic (mining) and natural (orogenic processes, volcanic activity) processes. To date there is no information on the level of Hg contamination and associated exposure. We sampled 8 river ecosystems from northern (18øS) to southern (54øS) extending across > 4,000 km. We hypothesized that there would be a negative latitudinal gradient of Hg bioaccumulation in the riverine top predators reflecting Chile?s geography and industrial activities. In each river, we collected rainbow and/or brown trout as they are the top predators. When possible, primary consumer invertebrates and sediments were also obtained. Methylmercury (MeHg) was quantified following U.S. EPA Method 1630 (2001), Acadia University. In addition, ?13C and ?15N stable isotope ratios were estimated via Elementar VisION EA-IRMS, Universidad de Antofagasta. MeHg in fish muscle ranged from 32.63 ng/g to 1,168 ng/g. Trout from the rivers associated with mining in the north of the country had significantly higher MeHg concentrations, following by rivers from areas where mining transitioned to agriculture. Urbanization had no obvious effect on MeHg bioaccumulation in trout. Interesting, a river from southern Patagonia in the south of Chile had significantly higher MeHg concentrations than central Chile. Across sites, trout had significantly higher MeHg concentration than macroinvertebrates, and the trophic biomagnification factor (TMF) ranged from 1.53 to 3.01. This is the first study in Chile to analyze MeHg distribution in freshwater ecosystems across such a latitudinal gradient capturing geographical and anthropogenic variation. Funded by FONDECYT 11180914

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