Mercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends

S. Guédron, D. Point, D. Acha, S. Bouchet, P. A. Baya, E. Tessier, M. Monperrus, C. I. Molina, A. Groleau, L. Chauvaud, J. Thebault, E. Amice, L. Alanoca, C. Duwig, G. Uzu, X. Lazarro, A. Bertrand, S. Bertrand, C. Barbraud, K. DelordF. M. Gibon, C. Ibanez, M. Flores, P. Fernandez Saavedra, M. E. Ezpinoza, C. Heredia, F. Rocha, C. Zepita, D. Amouroux

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Aquatic ecosystems of the Bolivian Altiplano (∼3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and monomethylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3–10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of MMHg were found in the filtered and unfiltered water rising up from <1 to ∼50% THg from the oligo/hetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high %MMHg is explained by a high in situ MMHg production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of MMHg due to abundant ligands present in these alkaline waters. Differences in MMHg concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in MMHg levels that also exist in their respective food webs. This suggests that in situ MMHg baseline production is likely the main factor controlling MMHg levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor MMHg production and thus accumulation in water and biota. High in situ MMHg production and accumulation in Lake Titicaca hydrosystem can be enhanced by local eutrophication and controls MMHg levels in fish species.

Original languageEnglish
Pages (from-to)262-270
Number of pages9
JournalEnvironmental Pollution
Volume231
DOIs
StatePublished - 2017

Bibliographical note

Funding Information:
This work is a contribution to the LA PACHAMAMA project (ANR CESA program, N o ANR-13-CESA-0015-01, PI: D. Amouroux: david.amouroux@univ-pau.fr), COMIBOL project (INSU CNRS/IRD EC2CO Program, PI: D. Point: david.point@ird.fr), EUTITICACA project (founded by the Impuestos Directos a los Hidrocarburos IDH administrated by the Universidad Mayor de San Andrés, PI: D. Achá: darioacha@yahoo.ca) and TRACISOMER supported by a grant from Labex OSUG@2020 (PI: S. Guédron: stephane.guedron@ird.fr). S. Guédron (ISTerre/IRD/UGA), C. Duwig and G. Uzu (IGE/IRD/UGA) are part of Labex OSUG@2020 (Investissements d'avenir – ANR10 LABX56).

Publisher Copyright:
© 2017 Elsevier Ltd

Keywords

  • Biota
  • Mercury
  • Sediment
  • Titicaca
  • Water

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