Impacts of crab bioturbation and local pollution on sulfate reduction, Hg distribution and methylation in mangrove sediments, Rio de Janeiro, Brazil.
Mercury (Hg) and methylmercury (MeHg) are highly toxic and poorly studied in mangroves. Burrowing Uca crabs change sediment topography and biogeochemistry and thus may affect Hg distribution and MeHg formation. We studied added (203)Hg distribution, Me(203)Hg formation and sulfate reduction rates (SRR) in sediment aquariums containing Uca leptodactyla; and analyzed profiles of Me(203)Hg formation and SRR in sediment cores from two mangroves with distinct environmental impacts. MeHg formation and SRR were higher in the top (≤6cm) sediment and there was no significant difference in Hg methylation in more or less impacted mangroves. In aquariums, crab bioturbation favored Hg retention in the sediment. In the treatment without crabs, Hg volatilization and water Hg concentrations were higher. Hg methylation was higher in bioturbated aquariums but SRR were similar in both treatments. These findings suggest that bioturbating activity favors Hg retention in sediment but also promotes MeHg formation near the surface.
Laboratório de Traçadores Wolfgang C. Pfeiffer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G/CCS/Ilha do Fundão, Rio de Janeiro (RJ), CEP: 21941-902, Brazil. Electronic address: raquel@biof.ufrj.br.
Raquel Rose Silva
RRS
Correia
Laboratório de Traçadores Wolfgang C. Pfeiffer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Bloco G/CCS/Ilha do Fundão, Rio de Janeiro (RJ), CEP: 21941-902, Brazil. Electronic address: jeanrdg@biof.ufrj.br.
Jean Remy Davée
JRD
Guimarães
D000818:Animals; D003386:Brachyura; D001938:Brazil; D019015:Geologic Sediments; D008628:Mercury; D008745:Methylation; D008767:Methylmercury Compounds; D013431:Sulfates; D014874:Water Pollutants, Chemical
D008767:Methylmercury Compounds; D013431:Sulfates; D014874:Water Pollutants, Chemical; D008628:Mercury
Biogeochemical cycle; Bioturbation; Gamma spectrometry; Liquid scintillation; Mass balance