Anthropogenic Impact of Mercury
Accumulation in Fish from
the Rio Madeira and Rio Negro Rivers
Faculdade de Ciências da Saúde and
Instituto de Química,
Universidade de Brasília, Brasília, Brazil
Received April 13, 2006; Revised June 2, 2006; Accepted July 18, 2006
Fish is an important concentrator of mono-methyl mercury and the
main route to human contamination. We compared fish Hg bioaccumu-
lation (within similar weight ranges) in two Amazonian river habitats
during high-water seasons. The Rio Madeira has been greatly impacted
by agriculture, alluvial gold extraction, and a hydroelectric reservoir,
whereas the Rio Negro is much less affected by these human activities.
The species at the top of the food web, Hoplias malabaricus (piscivorous;
80–668 ng Hg/g) and Cichla spp. (piscivorous; 42–747 ng Hg/g) showed
the highest range of Hg concentrations. Nonpiscivorous species with
comparable weight range, such as Potamorhina latior (detritivorous;
20–157 ng Hg/g) and Myleus torquatus (herbivorous; 2–182 ng Hg/g),
had lower Hg concentrations. Triportheus elongatus (omnivorous; 5–350
ng Hg/g), with the lowest weight range, also showed a low range of Hg
concentrations. Despite the Rio Madeira’s higher sediment load as well
as environmental impacts (deforestation, agriculture, hydroelectric reser-
voir, and alluvial gold mining) on natural Hg release, fish Hg bioaccu-
mulation was no different between the two river habitats for
nonpiscivorous species. In this small observational study only the species
at the top of the food web (M. torquatus, Cichla spp, T. elongatus) showed
higher mean Hg concentrations in the Rio Madeira than the dominantly
wilderness habitat of the Rio Negro.
Index Entries: Amazonia; inundation; floodplain; fish; Hg; gold min-
ing; Rio Negro; Rio Madeira.
Biological Trace Element Research
Vol. 115, 2007
© Copyright 2007 by Humana Press Inc.
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