Biomarkers for Mercury Exposure in Tropical Estuarine Fish

Abstract

Several studies have evaluated human risks due mercury (Hg) exposure through fish consumption. However, relatively few studies have explored effects of environmental Hg concentrations in biota, especially tropical fish species. The aim of this work was to assess in situ hematological, biochemical and genotoxic effects in tropical fish due to environmental exposure to mercury in estuarine ecosystems. A total of 282 fishes were collected from September 2003 to October 2005 in two estuarine areas: Ribeira Bay (reference area-22° 55' to 23° 02' S and 44° 18' to 44° 26' W) and Guanabara Bay (highly impacted area by human activities-22° 40' to 23° 00' S and 43° 00' to 43° 20' E). Total mercury levels in fish from Guanabara were twice higher than in Ribeira bay for the catfish species Genidens genidens (Ariidae), with significant differences among areas after standardization using length intervals (exposure time indicator). The species Haemulon steindachneri (Haemulidae) showed the highest mercury concentration, reflecting its position in trophic chain. Among effect biomarkers, only haematocrit, global leucometry and micronucleus assays seemed to reflect the differences on mercury exposure among areas, what may support their use for evaluations of fish exposure to mercury compounds. However, it's necessary both laboratory experiments to establish cause-effect relationship and a continuous in situ study to obtain more information, involving more trophic levels, searching for sensible species to mercury exposure.

Total Mercury in Carnivorous Fish from Brazilian Southeast

“…Monitoring programs also can limit the effect of fish size by sampling specimens over a narrow range of sizes, which facilitates comparisons between different sites and years (Henry et al 2004). The importance of standardizing the fish length was previously discussed by Rodrigues et al (2010), who stated that difference in the length and biomass of fish specimens can reflect different ages and consequently different periods of exposure in the environment. Often, when it is not possible to select all specimens with the same biometry, a way to standardize the sampling is classification by size categories.…”

“…Specimens were obtained directly from the same fishermen at Itaipu Embayment. Juveniles do not migrate, remaining in the estuary up to maturity (about 40 cm), which makes them good indicators of local environmental impacts (Kehrig 1992;Rodrigues et al 2010). For this reason, juvenile whitemouth croakers were chosen for this study.…”

Acetylcholinesterase Activity in Fish Exposed to Mercury in Guanabara Bay, RJ, Brazil

“…Mercury (Hg) is considered as one of the most toxic metals by the World Health Organization [17]. Some studies observed AChE inhibition due to mercury exposure [10], [12], [13], [18], [19], [20], [21], [22]. Jesus et al [23], [24], when considering neotropical fish species, evaluated possible effects on acetylcholinesterase activity and internal distribution of mercury in a carnivorous species (Hoplias malabaricus), using intraperitonial injections of mercury and methylmercury chlorides.…”

“…Machado et al [26] found an important gradient of mercury concentrations in superficial sediments, being the lowest concentration found at a protection area, with mangroves, at the Guapimirim River estuary (61.0 ng g -1 ) and the maximum concentration was described for Meriti River estuary (7,500 ng g -1 ), which has a chlor-alcali plant on the drainage basin. Low mercury concentrations in fish species have been reported [27], [28], however, risks to these animals health were already pointed out [21]. Therefore, the main objective of this study is to evaluate AChE activity as an effect biomarker for the ecological risk assessment related to mercury contamination in fish from Guanabara bay, Rio de Janeiro State, Brazil.…”

The ability of vitamin E, selenium and water to improve and recover the hematological, biochemical and hormonal parameters of mercury-exposed catfish Clarias gariepinus (Burchell, 1822)

“…Exposures of fish to different Hg concentrations in the Lap have shown several alterations in the behavior, growth performance, hematology, hormones and histopathological characteristics of the liver and kidney (Ibrahim, 2011). Also, many authors have reported that, mercury compounds can be retained in the animal tissues for long time, leading to irreversible damages, such as neurological impairment and lesions, behavioral and cognitive changes, ataxia, as well as convulsions, in addition to its harmful effect on gill arches, liver, kidney, hematological parameters, olfactory epithelium, and reproduction, alterations in enzymatic activities, problems during gonad development, reduction of eggs incubation success and survival during embryo-larval stages, decreased locomotors activity, reduction of escape capacity, brain lesions and death and genotoxic effects due to exposure of several fish species to Hg in the Lab ( Raldúa et al, 2007;Rodrigues et al, 2010;Zaki et al, 2011;Authman et al, 2015).…”