Human exposure to mercury: The three modern dilemmas

Rosa

Pereira

et al. 2006

Due to the lack of knowledge regarding annual bioaccumulation rates in estuarine and marine fauna, the main aim of this work was to study the annual mercury bioaccumulation in the well-documented bivalve species Scrobicularia plana along a human induced mercury gradient in the Ria de Aveiro coastal lagoon (Portugal) and in a nearby, non-polluted system (Mondego estuary), parallel to the risks associated with its consumption by humans.Minimum total mercury concentration was as low as 0.019 mg kg À1 (wwt) in 4þ year old organisms in the reference site, where a significant negative correlation ( p < 0.05) was found between total mercury concentrations and size, resulting in negative bioaccumulation rates (detoxification). On the other hand, values reached 1.8 mg kg À1 (wwt) in 3þ year old bivalves from the most contaminated area, where a strong positive correlation with size was found ( p < 0.01) and annual bioaccumulation rates were as high as 0.25 mg kg À1 yr À1 . Annual bioaccumulation rates were highly correlated with suspended particulate matter mercury concentrations. Even though the levels of organic mercury contents increased parallel to the contamination gradient, at each sampling station, no increment was found with age, which corresponded to a decrease in organic mercury percentage with age.In terms of ecological management and public health, the ratio of 0.01 consistently found between Scrobicularia plana annual mercury accumulation rates and SPM mercury levels for most sites may permit to roughly estimate S. plana contamination of commercial sized individuals (>2.5 cm) and, if verified and confirmed in other systems, be used as a simple management tool.

Section: Introductionmentioning

confidence: 99%

Pattern and annual rates of Scrobicularia plana mercury bioaccumulation in a human induced mercury gradient (Ria de Aveiro, Portugal)

Rosa

Pereira

et al. 2006

“…Problems derived from mercury contamination are enhanced when mercury enters the food chain, the predominant pathway of human exposure to methylmercury, which is the most toxic form of mercury (Tchounwou et al, 2003). Through the processes of biomethylation and bioaccumulation, methylmercury finds its way to species usually consumed by humans (Clarkson et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Macroalgae response to a mercury contamination gradient in a temperate coastal lagoon (Ria de Aveiro, Portugal)

Pereira

Duarte

et al. 2005

114

Primary producers represent an important pathway for mercury incorporation in aquatic food webs. With eutrophication processes occurring worldwide, macroalgae may represent a substantial pool of mercury, as a result of its high growth rate and capacity to bind trace metals. The main aim of this work was to evaluate the response of the macroalgae to a human-induced environmental mercury gradient in a temperate coastal lagoon, by assessing the total and organic mercury contamination levels of the dominant species (Enteromorpha, Fucus and Gracilaria). Total mercury in the plant tissues ranged from 0.02 to 2.1 mg g ÿ1 dwt. Fucus was the most contaminated algae, followed by Gracilaria and Enteromorpha. As a whole, organic mercury never exceeded 15% of total mercury content, but tended to increase with distance to metal source on all macroalgae indicating complex physiological responses from these primary producers in areas of high and low mercury concentrations. Sessile macroalgae may be important mercury immobilisation agents, while free-floating algae (Enteromorpha) play an important role in mercury transport from contaminated areas (G10 g ha ÿ1 ) to other areas of the lagoon and even to coastal waters. Based on the present results the use of macroalgal biomass from contaminated areas for direct or indirect human use (e.g. agricultural, industrial and food purposes) may result in health risks, due to the high bioaccumulation capacity (as high as 10 4 the dissolved mercury concentrations).

“…Methylmercury is more toxic, bioavailable and prone to bioaccumulation and biomagnification in estuarine food webs, ultimately finding its way to species usually consumed by humans (Wang et al, 1998;Clarkson et al, 2003;Tchounwou et al, 2003). Despite methylmercury typically being below 1% of total mercury in sediments, levels in fish are commonly above 90%, due to a higher biomagnification of the organic form (Lawson and Mason, 1998;Coelho et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

The role of two sediment-dwelling invertebrates on the mercury transfer from sediments to the estuarine trophic web

Nunes

Dolbeth

et al. 2008

The annual total and organic mercury bioaccumulation pattern of Scrobicularia plana and Hediste diversicolor was assessed to evaluate the potential mercury transfer from contaminated sediments to estuarine food webs. S. plana was found to accumulate more total and organic mercury than H. diversicolor, up to 0.79 mg kg À1 and 0.15 mg kg À1 (wet weight) respectively, with a maximum annual uptake of 0.21 mg kg À1 y À1 , while for methylmercury the annual accumulation was similar between species and never exceeded 0.045 mg kg À1 y À1 . The higher organic mercury fraction in H. diversicolor is related to the omnivorous diet of this species. Both species increase methylmercury exposure by burrowing activities and uptake in anoxic, methylmercury rich sediment layers. Integration with the annual biological production of each species revealed mercury incorporation rates that reached 28 mg m À2 y À1 , and to extract as much as 11.5 g Hg y À1 (of which 95% associated with S. plana) in the 0.4 km 2 of the most contaminated area, that can be transferred to higher trophic levels. S. plana is therefore an essential vector in the mercury biomagnification processes, through uptake from contaminated sediments and, by predation, to transfer it to economically important and exploited estuarine species.