title: Fish mercury increase in Lago Manso, a new hydroelectric reservoir in tropical Brazil.
abstract: It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level.
authors.affiliation: Department of Earth Sciences, Air & Water Science, Uppsala University, Villavägen 16, S-752 36 Uppsala, Sweden. Lars.Hylander@hyd.uu.se
authors.forename: Lars D
authors.initials: LD
authors.lastname: Hylander
authors.forename: Janina
authors.initials: J
authors.lastname: Gröhn
authors.forename: Magdalena
authors.initials: M
authors.lastname: Tropp
authors.forename: Anna
authors.initials: A
authors.lastname: Vikström
authors.forename: Henriette
authors.initials: H
authors.lastname: Wolpher
authors.forename: Edinaldo
authors.initials: E
authors.lastname: de Castro E Silva
authors.forename: Markus
authors.initials: M
authors.lastname: Meili
authors.forename: Lázaro J
authors.initials: LJ
authors.lastname: Oliveira
mesh_terms: D000535:Aluminum; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D001938:Brazil; D005399:Fishes / Q000254:growth & development / Q000378:metabolism*; D019015:Geologic Sediments; D007501:Iron; D008345:Manganese; D008628:Mercury / Q000032:analysis* / Q000378:metabolism; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D011210:Power Plants; D045483:Rivers; D012989:Soil Pollutants / Q000378:metabolism / Q000494:pharmacology; D014329:Tropical Climate; D014873:Water Pollutants / Q000378:metabolism / Q000494:pharmacology
chemical_list: D012989:Soil Pollutants; D014873:Water Pollutants; D008345:Manganese; D000535:Aluminum; D007501:Iron; D008628:Mercury