Transfer of mercury and methylmercury along macroinvertebrate food chains in a floodplain lake of the Beni River, Bolivian Amazonia

MOLINA, CARLOS ISRAEL; GIBON, FRANCOIS MARIE; DUPREY, JEAN-LOUIS; DOMINGUEZ, EDUARDO; GUIMARÃES, JEAN-REMY D.; ROULET, MARC

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Año: 2010 vol. 408 p. 3382 - 3391

0048-9697

We have evaluated the mercury and methylmercury transfers to and within the macroinvertebratecommunities of a floodplain lake of the Beni River basin, Bolivia, during three hydrological seasons and intwo habitats (open water and vegetation belt). Using the stable isotopes δ13C and δ15N, six trophic chainswere identified during a previous study. Four are based on only one source: seston, organic matter from thebottom sediment, periphyton and macrophytes. Two are based on mixed sources (seston and periphyton inone case, periphyton and macrophytes in the other). During sampling, we found only one taxon that hadsurface sediment organic matter as food source and very few taxa whose trophic source was constituted bymacrophytes. The periphyton was the most important source during all seasons; it produced the longestchain, with three trophic positions. Whatever the season and trophic source, all collected macroinvertebratescontained methyl mercury and the latter was biomagnified in all trophic chains that we identified. Thebiomagnification of methylmercury through invertebrate trophic chains accurately reflected the existenceand length of these chains. Biomagnification was virtually non-existent in the sediment-based chain, low andrestricted to the dry season in the macrophyte-based chain. It was significant in the seston-based chain, butlimited by the existence of only two trophic levels and restricted to the wet season. Finally, it was veryeffective in the periphyton-based chain, which offers the highest rate of contamination of the source but,above all, the largest number of trophic levels.