Mercury in freshwater, estuarine, and marine fishes from Southern Brazil and its ecological implication

Mercury toxicology in Epinephelidae fishes: A multiple tissue approach in two groupers species from southwestern Atlantic (SE-Brazil)

Epinephelidae fishes are important to reef ecosystems, as well as for commercial fishing and cultural heritage. Additionally, most of these species are at some risk of extinction, as Epinephelus marginatus and Hyporthodus nigritus. This study aimed to determine total mercury (THg) concentrations and burden on eight tissues of E. marginatus and H. nigritus. A Cold Vapor/Atomic Absorption Spectrometer was used for the THg determination. THg concentrations and burden varied significantly between tissues in both species. The highest concentrations were determined in the liver, and the greatest burden was in muscle. The gonad concentrations were higher than the toxicological threshold. General trends of increase in THg concentrations and burden along growth were observed. Mercury is a threat for both species evaluated, raising this concern for other Epinephelidae species.

Mercury distribution in water masses of the South Atlantic Ocean (24°S to 20°S), Brazilian Exclusive Economic Zone

Mercury (Hg) is a toxic globally spread pollutant that has been found at increasing concentrations in the South Atlantic Ocean. The present work provides the first insight into the total mercury (HgT, unfiltered waters) content in the water of the Brazilian Exclusive Economic Zone (BEEZ), within a 24°S to 20°S. Water samples were collected from surface to 3400 m depth along transects, and analyzed with atomic fluorescence. The mean HgT concentration for the Tropical Water mass (TW) was 6.3 ± 1.4 pM (n = 16), for the South Atlantic Central Water (SACW), 5.9 ± 0.7 pM (n = 8), for the Antarctic Intermediate Water (AAIW), 5.0 ± 0.6 pM (n = 2), for the Upper Circumpolar Deep Water (UCDW), 6.5 pM (n = 1), and for the North Atlantic Deep Water (NADW), 5.7 ± 0.9 pM (n = 12). HgT concentrations were highest throughout the BEEZ in comparison with other parts of the Atlantic Ocean, farther from the coast.

Mercury Concentrations in Four Marine Fishery Resources from Rio de Janeiro Coast, SW Atlantic, and Potential Human Health Risk Via Fish Consumption

Mercury (Hg) contamination has caused ecological and socioeconomic problems worldwide. One of the main Hg contamination routes by the human populations is through fish ingestion. Herein, we analyzed the total Hg concentrations (THg) in highly consumed marine fish species: Brazilian flathead Percophis brasiliensis, Atlantic bigeye Priacanthus arenatus, Stripped weakfish Cynoscion guatucupa, and Jamaica weakfish C. jamaicensis. The specimens were collected from fishing landings off the Rio de Janeiro, SW Atlantic. Additionally, we calculate the estimated weekly intakes (EWI) and the maximum amount of fish (MAF) that can be safely ingested, both based on the provisional tolerable weekly intake (PTWI). The highest THg concentrations were recorded in P. brasiliensis with a mean of 340.59 μg/kg (dry weight) and the lowest in P. arenatus (115.75 μg/kg). THg concentrations were positively related to the δ¹⁵N ratios indicating an increase in contamination with trophic level. All samples showed THg concentrations below the established limits by Brazilian and international regulation. Hg intake via human fish consumption does not exceed the PTWI. The EWI varied from 1.41% (P. arenatus size class I) to 11.52% (P. brasiliensis class II) of the PTWI, while the estimated EWI for "fish consumers" varied between 8.35 and 68.07% PTWI. The MAF estimated for an adult (70 kg) could safely consume between 1277.85 and 7075.50 g/week. This study is an important baseline for monitoring and future comparisons. Therefore, it is important to maintain monitoring of mercury levels in fish species in different marine regions, especially those species most consumed by humans.

Angel sharks (Squatinidae): A review of biological knowledge and exploitation

Angel sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshore-offshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of angel shark populations with fisheries and other human activities. Their dorso-ventrally flattened body shape, large size (most species attain >100 cm total length, L_T ) and demersal nature means that they may be taken in a variety of demersal fishing gears from birth. Available data indicate that angel sharks typically have a biennial reproductive cycle, with litter sizes generally <20 and the young born at c. 20-30 cm. The biological characteristics of angel sharks render them susceptible to overexploitation, as exemplified by the decline of Squatina squatina from many parts of its former range in the north-east Atlantic and Mediterranean Sea. Currently, half of the 22 recognized extant species of angel shark are classed as Threatened on the International Union for Conservation of Nature (IUCN) Red List (with a further three classified as Data Deficient). Given the biological vulnerability of angel sharks, and that many species are data-limited, the current paper provides a review of available biological information and fisheries data pertaining to this family.

Polycyclic aromatic hydrocarbons in wild and farmed whitemouth croaker and meagre from different Atlantic Ocean fishing areas: Concentrations and human health risk assessment

This work assessed the concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) in edible tissues of whitemouth croaker (Micropogonias furnieri) and meagre (Argyrosomus regius) captured in different Atlantic Ocean fishing areas and available to Brazilian and Portuguese consumers. Total PAH (∑PAHs) levels ranged from 1.32 to 5.41 μg/kg ww in wild-caught croaker and 2.66 (wild)-18.0 (farmed) μg/kg ww in meagre. Compounds with 2- and 3-rings represented 54-86% of ∑PAHs in the muscle tissues of wild-caught species (croaker and meagre) being naphthalene, fluorene, and phenanthrene the predominant compounds. ∑PAHs in farmed meagre were 4-7 times higher than in wild-caught meagre, with 2-, 3-, 4-, 5-, and 6-ring compounds representing 15, 18, 44, 22, and 1% of ∑PAHs, respectively. Benzo(a)pyrene levels in farmed meagre varied between 0.06 and 0.34 μg/kg ww. Crude oil refining and combustion sources were identified as the major sources of PAHs in FAO 27, 34 and 41 Atlantic Ocean fishing areas. The biometric characteristics (length, weight, moisture, and fat content) and ∑PAHs allowed to discriminate between wild-caught and farmed meagre samples and between meagre and croaker. Assessment of carcinogenic risks suggested that a diet exclusive on farmed meagre may pose additional risks for the health of European top consumers fish.

Mercury distributions in sediments of an estuary subject to anthropogenic hydrodynamic alterations (Patos Estuary, Southern Brazil)

The city of Rio Grande, located on the right bank of the Patos Estuary, has been severely contaminated by mercury (Hg) due to anthropogenic activities that chiefly began in the eighteenth century. To investigate the natural mercury distribution along the salinity gradient in the estuary, three sediment cores were collected from a region of the estuary that has experienced less anthropogenic impacts, namely its left bank. Our study demonstrates that accumulation of Hg and formation of metal sulfide minerals take place in fine grain sediment horizons within the sampled sediment cores. Mercury immobilization in these sediments occurs via binding to organic matter coatings on fine grain sediment particles, as well as by incorporation into and/or co-precipitation with iron sulfide minerals. The grain size controls over Hg accumulation and sulfide mineral formation were statistically demonstrated using principal component analysis. Different fine particulate sediment deposition patterns occurred at each sampling location, which is attributed to the consequence of hydrological changes in the estuary resulting from navigation infrastructure reforms performed over the past 200 years in the local port (e.g., dredging) and its surroundings. We suggest that the port building and maintenance activities have influenced Hg distributions in the estuarine sediments.

Mercury in aquatic fauna contamination: A systematic review on its dynamics and potential health risks

Mercury is an important pollutant, released into aquatic ecosystems both naturally and by anthropogenic action. This element is transferred to aquatic organisms in different ways, causing potential health risks. In addition, mercury can be accumulated by humans, especially through the consumption of contaminated food. This systematic review aims to present mercury pathways, the major routes through which this element reaches the aquatic environment and its transformations until becoming available to living animals, leading to bioaccumulation and biomagnification phenomena. The key biotic and abiotic factors affecting such processes, the impact of mercury on animal and human health and the issue of seafood consumption as a source of chronic mercury contamination are also addressed. A total of 101 articles were retrieved from a standardized search on three databases (PubMed, Emabse, and Web of Science), in addition to 28 other studies not found on these databases but considered fundamental to this review (totaling 129 articles). Both biotic and abiotic factors display fundamental importance in mediating mercurial dynamics, i.e., muscle tropism, and salinity, respectively. Consequently, mercurial contamination in aquatic environments affects animal health, especially the risk of extinction species and also on human health, with methylmercury the main mercury species responsible for acute and chronic symptomatology.

Record of Hg pollution around outset of colonization in Southern Brazil

This study presents results of a sediment core located in Coroa de Boi Bay, a not dredged cove within Patos Estuary, Southern Brazil. The distribution of metals (Hg, Cu, Pb) and U in the sediment profile records several contamination events since pre-colonial times to present days. A joint assessment of the distribution of these parameters and the consultation to historical documents allowed us to establish causal links between concentrations anomalies in the sediments and ancient anthropogenic contamination in the area. During the industrial period, sedimentation rates in the bay ranged from 3.4 to 5.5 mm year^-1. Applying a sedimentation rate previously calculated for undisturbed sediments in the Patos Estuary, we trace the beginning of Hg contamination as having started in the colonial period in Southern Brazil, soon after a Hispanic-Lusitanian conflict situation in South America. The most probable source of Hg contamination during this period was carroting technology used in fur processing.

Total mercury concentrations in white and striped Mullet (Mugil curema and M. cephalus) from a coastal lagoon in the SE Gulf of California

The White and Striped mullets (Mugil curema and M. cephalus) are highly abundant and commercially important estuarine fish in northwest (NW) Mexico. Because of their feeding habits and habitat, they are likely to accumulate mercury (Hg) in their muscle and liver. The objectives of this study were to determine total Hg distribution in the tissues of interest, to correlate Hg levels between tissues and with length and weight of fish, to estimate the percentage weekly intake (PWI) of total Hg and methyl Hg (MeHg) through consumption of both mullet species, and to compare total Hg levels with mullets from other areas. The highest total Hg concentration (1.031 µg g^-1 dry weight) was measured in liver of White mullet. In both species, the order of averaged Hg concentrations (M. curema liver 0.272, muscle 0.184; M. cephalus liver 0.211, muscle 0.129 µg g^-1 dry weight) were liver>muscle. Correlations of Hg in muscle and liver with total weight of M. curema were significant. In M. cephalus, Hg levels in liver were significantly correlated with total length and weight. The PWI of THg (<4%) and MeHg (<10%) were not elevated for both species. Concentration of Hg in the studied mullets was comparable to levels in similar species from Mexican waters but lower than results in mugilids from other coastal areas.

Mercury concentrations in dusky grouper Epinephelus marginatus in littoral and neritic habitats along the Southern Brazilian coast

Our study incorporated a comprehensive suite of parameters (i.e., body size, age, diet and trophic position) to investigate mercury concentration in dusky groupers Epinephelus marginatus. This study was carried out in rocky bottoms in littoral and neritic habitats along the Southern Brazilian coast. We also determined spatial variation in mercury concentrations in individuals inhabiting both zones, which may provide insights into how dietary differences or potential pollution sources affect bioaccumulation. A total of 244 dusky groupers was analyzed to determine total mercury concentrations. Our study revealed that when considering similar body sizes, individuals inhabiting littoral rocky habitats had higher concentrations of mercury probably due to proximity to pollution sources associated with human activities in the estuary and its drainage basin. Furthermore, large individuals (>650mm and >8years old) showed mercury contamination levels that are potentially harmful for this endangered fish species and above the acceptable limits for human consumption.

Mercury (Hg) in fish consumed by the local population of the Jaguaribe River lower basin, Northeast Brazil

The knowledge of Hg concentrations in fish is of considerable interest since these organisms are a major source of protein to coastal human populations and fishing communities. The main source of human exposure to Hg contamination occurs through the consumption of fish. In this paper, we compare Hg concentration in 13 fish species from Jaguaribe River lower basin and an adjacent coastal region in the northeastern coast of Brazil. We sampled fish from three stretches of the river: fluvial, estuarine, and marine regions. We tested the hypothesis that Hg concentration in muscle tissue vary according to species, location, and trophic level. Significant differences were observed among species and trophic level, but these could not be observed among the regions studied. As expected, the highest concentrations were observed in carnivorous fish (5.6-107.5; 26.9 ± 18.8 ng g(-1)). Hg concentrations observed in this study are similar to those observed in regions of low environmental contamination. We estimated Hg intake to vary between 0.02 and 0.22 ng Hg kg body weight(-1) week(-1), for the average body weight of 56.7 kg, which was considered as low exposure and therefore, a low risk to consumers of fish from the regions studied.

Comparative analysis of total mercury concentrations in anadromous and non-anadromous Arctic charr (Salvelinus alpinus) from eastern Canada

Previous research has documented that total mercury concentrations ([THg]) are lower in anadromous Arctic charr than in non-anadromous conspecifics, but the two life-history forms have rarely been studied together. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual [THg] across a range of latitudes (49-81° N) in eastern Canada. Unadjusted mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations, ranging from 111 to 227 ng/g ww. Within-population variations in [THg] were best explained by fish age, and were often positively related to fork-length and δN-inferred trophic level. Differences in [THg] were not related to differences in length-at-age (i.e., average somatic growth rate) among populations of either life-history type. Mercury concentrations were not related to site latitude in either the anadromous or non-anadromous fish. We conclude that the difference in Arctic charr [THg] with life-history type could not be explained by differences in fish age, fork-length, trophic position, or length-at-age, and discuss possible factors contributing to low mercury concentrations in anadromous, relative to freshwater, fish.

Ecological and biological determinants of methylmercury accumulation in tropical coastal fish

This research investigated whether environmental conditions, biological fish characteristics and anthropogenic impacts influenced mercury (Hg) assimilation into the muscle tissue of two fish species from two Brazilian bays, Ilha Grande Bay and Guanabara Bay. Fish and superficial water were collected in different periods. Hg was determined by CV-AAS. Methylmercury (MeHg) was identified and quantified by ECD-GC. Chlorophyll a concentrations in the water column indicated that Ilha Grande Bay and Guanabara Bay were oligotrophic and eutrophic, respectively. Hg in fish ranged from 2.10 to 870.17 μg kg(-1) dry wt. in Ilha Grande Bay and 40.90 to 809.24 μg kg(-1) dry wt. in Guanabara Bay. Slight differences were found between the length-normalized Hg concentrations and its percent of Hg in a voracious predator from the bays. In Guanabara Bay, where the presence of a chlor-alkali plant causes Hg input, the iliophagous fish species showed the highest length-normalized Hg concentrations and the voracious predator the lowest. Iliophagous fish is consumed by voracious predator and, consequently, acts as their MeHg food supply. Iliophagous fish from Ilha Grande Bay presented a higher percent of MeHg (80.0 %) than specimens from Guanabara Bay (54.5 %). This fact suggests that more MeHg was transferred from iliophagous fish to voracious predator in Ilha Grande Bay. At Guanabara Bay, the bioproduction is greater than that at Ilha Grande Bay, presenting the highest biomass in it ecosystem, which may subsequently dilute Hg and reduce its availability to the biota; i.e., influencing in Hg and MeHg availability throughout the food chain. Consequently, more MeHg is available in the aquatic environment of Ilha Grande Bay.