Simultaneous radioassays of bacterial production and mercury methylation in the periphyton of a tropical and a temperate wetland

Cyanobacteria enhance methylmercury production: A hypothesis tested in the periphyton of two lakes in the Pantanal floodplain, Brazil

“…Most of the literature states that the process of methylation is complex and most efficiently produced under low pH, high DOC, moderately high temperatures and low oxygen conditions favourable to anaerobic SRB (Ikingura and Akagi, 1999;Ulrich et al, 2001;Guimarães et al, 2006). Based on our data, the dissolved oxygen concentration and pH in the lakes would facilitate Hg methylation especially during flood stage.…”

“…Contamination by mercury (Hg) in aquatic ecosystems is of concern, as such it is important to monitor potential sources of this metal to aquatic environments and to understand the complex biogeochemical cycle (Guimarães et al, 2006;Carrasco et al, 2011a). Mercury occurs in different physical and chemical forms in aquatic systems.…”

“…Recent studies on MeHg production in tropical floodplain environments (Guimarães et al, 2006;Correia et al, 2012) showed that the root zone of floating macrophytes produced more MeHg than the water column and sediments of the open water zones of lakes and river, and also sustained very high net methylation rates. Roulet et al (2000) showed that periphyton communities in roots are the first link in the food chain and one of the main MeHg sources in the lower Tapajós river valley, Brazil.…”

Non-lethal sampling for mercury evaluation in crocodilians

“…Previous studies demonstrate that MeHg production increases during the flooding phase of the flood pulse in tropical areas, due to greater decomposition of land organic matter incorporated into the body of water, by the creation of lower dissolved oxygen in water habitats, and by the higher density of periphyton associated with the roots of aquatic macrophytes in water ecosystems during this period. Higher periphyton density is linked to higher rates of primary methylation (Guimarães et al, 2006;Ulrich et al, 2001;Lázaro et al, 2013).…”

Mercury distribution in sediments of a shallow tropical reservoir in Brazil

“…Once inside the epilimnion of the reservoir, Hg can either be eliminated towards the atmosphere after photochemical reduction (Xiao et al 1995, Peretyazhko et al 2006, transferred to the hypolimnion after adsorption on particulate matter (like other heavy metals), or undergo further transformations such as methylation (Guimarães et al 2006) or (co)precipitation (e.g., with Fe species; Bura-Nakić et al 2013).…”