Bioaccumulation and biomagnification of mercury in African lakes: The importance of trophic status

Abstract

Despite the global prevalence of both mercury (Hg) contamination and anthropogenic eutrophication, relatively little is known about the behavior of Hg in eutrophic and hypereutrophic systems or the effects of lake trophic status on Hg uptake and trophodynamics. In the current study we explore Hg trophodynamics at 8 tropical East African study sites ranging from mesotrophic to hypereutrophic, in order to assess the influence of lake trophic status on Hg uptake and biomagnification. Comprehensive water, plankton and fish samples were collected for analysis of total mercury (THg) and stable carbon and nitrogen isotopic ratios. We found evidence that uptake of THg into phytoplankton tended to be lower in higher productivity systems. THg concentrations in fish were generally low, and THg trophic magnification factors (TMFs; representing the average increase in contaminant concentrations from one trophic level to the next) ranged from 1.9 to 5.6. Furthermore TMFs were significantly lower in hypereutrophic lakes than in meso- and eutrophic lakes, and were negatively related to chlorophyll a concentrations both across our study lakes, and across African lakes for which literature data were available. These observations suggest that THg concentrations were strongly influenced by trophic status, with year-round high phytoplankton and fish growth rates reducing the potential for high THg in fish in these productive tropical lakes.

Hg Concentrations in Muscles and Gills of Fish from Shallow Lakes of Different Trophic Status (Eastern Poland)

“…1). A similar negative correlation between Hg accumulation and chlorophyll a concentration has been found in some species of fish in North America (largemouth bass Micropterus salmoides, smallmouth bass Micropterus dolomieu, walleye Sander vitreus, and yellow perch Perca flavescens) [30], and in many species of fish in African lakes [19].…”

“…Previous studies of Hg content in fish have mainly dealt with Scandinavian ecosystems [12][13][14], marine environments [15][16] or the large ecosystems of American and African lakes [17][18][19][20][21]. Considerably fewer studies have dealt with Hg contamination of fish in shallow lakes in the temperate zone [22].…”

Biofilms grown in aquatic microcosms affect mercury and selenium accumulation in Daphnia

“…Significant differences were observed between the two biofilm treatments for set 1 only (***P < 0.001; ns not significant). The y-axis is on a logarithmic scale with base 2 where the concentration of metals within cells is diluted by growth during the day (measured as photosynthetically fixed carbon) (Hill and Larsen 2005;Poste et al 2015). Hill and Larsen (2005) showed how this phenomenon substantially decreased metal concentrations in biofilm within a short period of 4 days, equal to the duration of the current experiment.…”

Impacto De La Minería Del Oro Asociado Con La Contaminación Por Mercurio en Suelo Superficial De San Martín De Loba, Sur De Bolívar (Colombia)

“…El mercurio (Hg) es un elemento tóxico que se bioacumula y biomagnifica a través de la cadena tró-fica (Poste et al 2015), constituyendo una amenaza para la salud humana (Li y Tse 2015). La contaminación por Hg puede deberse a fuentes naturales tales como volcanes, erosión del suelo y océanos, o bien a fuentes antrópicas tales como combustibles fósiles (Feng et al 2002), producción de metales (Feng et al 2004), minería del oro (Olivero-Verbel et al 2015) y plantas de cloro-álcali (Qi et al 2000), entre otras, siendo la minería aurífera la principal causa de contaminación ambiental por este metal debido a la utilización de mercurio metálico para formar amalgamas con el oro durante la extracción del oro (Niane et al 2014).…”