Biofilm and mercury availability as key factors for mercury accumulation in fish (Curimata cyprinoides) from a disturbed amazonian freshwater system

The Petit‐Saut hydroelectric reservoir was filled in 1994 on the Sinnamary River in French Guiana (Amazonian basin). Flooding of the equatorial rain forest led to anoxia in most of the water column and enhanced mercury methylation in the reservoir hypolimnion. We selected the benthivorous/omnivorous...

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Bibliographic Details
Published in:Environmental toxicology and chemistry 2007-01, Vol.26 (1), p.45-52
Main Authors: Dominique, Yannick, Maury-Brachet, Régine, Muresan, Bogdan, Vigouroux, Régis, Richard, Sandrine, Cossa, Daniel, Mariotti, André, Boudou, Alain
Format: Article
Language:English
Subjects:
Amazonian hydroelectric reservoir
Animals
Anoxia
Aquatic ecosystems
Bioaccumulation
Bioavailability
Biofilms
Carbon isotopes
Comparative studies
Contamination
Curimata cyprinoides
Downstream
Feeding Behavior
Field study
Fish
Fishes
France
Fresh Water
Hydrochloric acid
Hypolimnion
Invertebrates
Mercury
Mercury - pharmacokinetics
Methylmercury
Microorganisms
Organic matter
Rainforests
Reservoirs
Rivers
Water column
Water flow
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Summary:The Petit‐Saut hydroelectric reservoir was filled in 1994 on the Sinnamary River in French Guiana (Amazonian basin). Flooding of the equatorial rain forest led to anoxia in most of the water column and enhanced mercury methylation in the reservoir hypolimnion. We selected the benthivorous/omnivorous fish species Curimata cyprinoides to investigate total mercury and methylmercury (MeHg) bioavailability and bioaccumulation capacities in the reservoir and downstream in the Sinnamary River. Mercury concentrations in the dorsal skeletal muscle were 10‐fold higher in fish from the downstream zone. Stomach contents and stable nitrogen and carbon isotope ratios showed that biofilms and the associated invertebrate communities represented important food sources at the two sites. The δ13C measurements indicated that biofilms in the flooded forest zone of the reservoir consist of endogenous primary producers; downstream, they are based on exogenous organic matter and microorganisms, mainly from the anoxic layers of the reservoir. Total mercury and MeHg concentrations in the biofilms and associated invertebrates were much higher at the downstream site compared to concentrations at the reservoir. Our results clearly show the importance of MeHg export from the anoxic layers of this tropical reservoir. We conclude that differences between biofilm composition and MeHg concentrations in the ingested food could explain the marked differences observed between mercury levels in fish.
ISSN:0730-7268
1552-8618
DOI:10.1897/05-649R.1