Mercury distribution in key tissues of fish (Liza aurata) inhabiting a contaminated estuary—implications for human and ecosystem health risk assessment

Abstract

This study brings a new viewpoint based on multiple-tissue analyses to form the basis for a predictive mode of mercury accumulation dynamics in fish body under field conditions. Total mercury (T-Hg) was determined in key tissues of Liza aurata captured along an estuarine contamination gradient, displaying the following hierarchy: kidney > liver > muscle > brain > gills > blood. Brain was the tissue that better reflected the mercury contamination extent, closely followed by liver and muscle. Organic mercury (O-Hg) measured in muscle and liver represented more than 85% and less than 30% of the T-Hg, respectively. The lowest O-Hg percentage was found in the most contaminated area, for both muscle and liver. Mercury distribution and accumulation patterns showed dependence on the specific tissue. The high mercury levels found in organs involved in vital physiological processes point out the risk to autochthonous fish fauna. Human risk associated to the ingestion of fish living in the surveyed areas cannot be excluded.

Risk Assessment of Heavy Metals in Imported Frozen Fish Scomber scombrus Species Sold in Nigeria: A Case Study in Zaria Metropolis

“…This was also found to be far above the concentrations reported by other studies in the Mediterranean Sea on fish tissues [34,46,47]. [48]. Mieiro et al [49] show that fish brain serves as the major critical target of mercury in the environmentally exposed fish.…”

Evaluation of Species-Specific Dissimilarities in Two Marine Fish Species: Mercury Accumulation as a Function of Metal Levels in Consumed Prey

“…Our results suggest an improvement in the condition of the estuary given that the maximum observed T-Hg concentrations in D. labrax's muscle never exceeded 0.47 mg kg -1 , a threefold decrease in less than a decade. Regarding L. aurata, studies of the system are recent (Mieiro et al 2009;Guilherme et al 2008), and T-Hg concentrations in juvenile specimens were in the same range as reported here for gills, liver, brain, and muscle, suggesting that the area may have attained a steady state concerning Hg contamination in the last few years. Studies on contaminant distribution and accumulation in organisms may confer insight into specific bioaccumulation pathways, the knowledge of which is fundamental to assess the relative input of the various environmental compartments in accumulation as well as define appropriate quality guidelines for water and sediments (Wang and Fisher 1999).…”

“…Regarding gills, no significant differences were observed between the two species for both T-Hg and O-Hg bioaccumulation, confirming this tissue' ability to reflect metal bioavailability in the water column, with which they come into close and permanent contact. Gills were one of the least contaminated tissues, a consequence of the frequent renewal through exfoliation and erosion to which it is subject, as suggested previously (Mieiro et al 2009). …”

“…The low levels observed in brain tissue suggest some degree of protection from metal toxicity, possibly through transport limitation at the brain-blood barrier (Zheng et al 2003) and through a buffering action exerted by other organs and tissues, such as muscle, liver and kidney, thus protecting brain especially against organic Hg (Mieiro et al 2009). Our results are in agreement with previous research, suggesting that uptake rates of both organic and inorganic Hg are particularly low in the brain compared with other organs (Niimi and Kissoon 1994).…”

Comparison of a toxicokinetic and a questionnaire-based approach to assess methylmercury intake in exposed individuals

“…The corresponding MeHg concentrations were calculated considering that 90% of total mercury in fish is found in the methylated form (WHO, 1990;Cabanero et al, 2007;Xue et al, 2007;Mieiro et al, 2009) …”