Mercury as a pollutant in aquatic ecosystems
Mercury is a highly toxic pollutant that rapidly spreads all over the world from its natural and anthropogenic sources. Although atmospheric mercury concentrations have been decreased by 20 to 38% since 1996 (Slemr et al. 2011), mercury pollution is still a severe threat to aquatic ecosystems. Recent causes of mercury pollution in aquatic ecosystems include oil and coal combustion, agricultural drain water and atmospheric deposition from electric power generation (Pacyna et al. 2006; Wolfe et al. 1998). As well, the ongoing climate change is supposed to induce processes enhancing the Hg emission (Slemr et al. 2011). Mercury is present in aquatic waters as elemental mercury, mono/dimethyl mercury, divalent mercury, colloidal mercury and particulate mercury. The ability of biomagnification, i.e. an increase in concentration in biomass at…show more content… Therefore, predaceous birds have often been used in monitoring the effects of mercury toxicity in aquatic ecosystems. Overall, contamination will result in neurotoxicity, embryotoxicity, impaired physiological function, endocrine disruption and altered reproductive behaviour (Wolfe et al. 1998). The major toxic effects in birds are central nervous dysfunctions, mostly characterised by spinal cord degeneration (Scheuhammer 1987). Clinical symptoms are a reduced food intake leading to weight loss, weakness of muscles leading to difficulty in flying, walking and standing, and the inability to coordinate muscle movements. The most sensitive response to mercury pollution is reproduction, which is already affected by very low concentrations. Factors reducing the reproduction are reduced hatchability due to an increased embryo mortality, eggshell thinning, reduced clutch size, increased numbers of eggs laid outside the nest and aberrant behaviour of juveniles (Wolfe et al.