Mercury and selenium in three fish species from a dam 20 months after a mine-tailing spill in the SE Gulf of California ecoregion, Mexico.

During January 2013, a mining spill occurred in the Santa Maria mining region, releasing around 300,000 m3 of tailings on Los Remedios river, which was transported through the San Lorenzo river and finally to El Comedero (EC) dam. Twenty months later, we examined the concentrations of Hg and Se in the muscle, liver, gills, and guts of three fish species (Cyprinus carpio, Oreochromis aureus, Micropterus salmoides) captured in the EC dam to assess the performance of the cleaning operations. A high Se concentration in the liver of all species (carp, 1.2 ± 0.4; tilapia, 3.9 ± 2.1; bass, 3.5 ± 1.1 µg g-1 ww) was consistently observed, while this behavior was only found in the blue tilapia for Hg (0.15 ± 0.11 µg g-1 ww). Tilapia (benthic-detritivorous) exhibited the highest Se concentrations compared to the carp (omnivore) and the largemouth bass (piscivore). In contrast, the largemouth bass had the highest Hg levels in the muscle compared with the other fishes. Such differences could be related to the different metabolism and feeding habits among species. Compared to a tilapia study carried out three months after the mine spill during a mortality event, a decrease was evident in the liver for Se and Hg by 7.2 and 4.7 times, respectively. This reveals that cleaning operations were more efficient for Se and less for Hg, and that a prolonged period was required for the partial recovery of the element levels in fish from sites impacted by mining. Considering the Mexican consumption scenarios for each fish species, it could be concluded that there will be no non-cancer risk by exposure to Hg or Se.

Mercury, selenium, and stable carbon and nitrogen isotopes in the striped marlin Kajikia audax and blue marlin Makaira nigricans food web from the Gulf of California.

Mercury (Hg) concentrations based on dietary sources have shown to predict differences in fish; however, they are usually applied at an individual scale and are rarely directed at a known trophic transfer. We combined gut content analysis and stable isotope analysis (δ15N and δ13C) to provide a quantitative estimate of Hg and selenium (Se) biomagnification in the striped marlin (Kajikia audax) and blue marlin (Makaira nigricans) food web from the southwestern Gulf of California. Hg and Se concentrations (mean ± SD; µg g-1, dw) were different among K. audax (Hg = 3.6 ± 2.1, Se = 5.5 ± 5.4) and M. nigricans (Hg = 19.0 ± 29.6, Se = 8.8 ± 10.5). Such variations of element concentrations could be linked to predation with different Hg and Se contents. Diet data presented as prey weight (%W) indicated a higher proportion of large prey fish for the blue marlin than the striped marlin. δ15N and δ13C indicated pelagic food sources with epipelagic preferences for the blue marlin and mesopelagic for the striped marlin. The relationship between Hg concentrations and δ15N was positive along the food web of both marlin species, indicating biomagnification of Hg. However, Se biomagnification was not clearly evidenced, and Se:Hg ratios decreased with δ15N, attributed to increasing Hg concentrations with increased trophic level.

Mercury and selenium biomagnification in a coastal food web from the Gulf of California influenced by agriculture and shrimp aquaculture.

The biomagnification of Hg and Se was studied using nitrogen stable isotope analysis during four seasons in a coastal lagoon of the eastern central Gulf of California. This lagoon receives agricultural, municipal, and shrimp aquaculture effluents. The species were categorized into organism groups and presented a significant accumulation of Hg and Se with respect to the sources, while the concentration of both elements in sediment and suspended particulate matter (SPM) was low. Our data confirms the positive transfers (biomagnification factors >1) of Hg and Se in the entire studied food web, and it was structured in five trophic levels across all seasons. Additionally, there were no linear correlations between the molar Se:Hg ratios and the trophic levels of the organism groups. However, the Se:Hg ratios among organism groups were >1, which indicates that there is an excess of Se and that it is not a limiting factor for the detoxification of Hg.

The spotted ratfish Hydrolagus colliei as a potential biomonitor of mercury and selenium from deep-waters of the northern Gulf of California.

The purpose of this work was to use the deep-water chimaera Hydrolagus colliei to examine the bioaccumulation and availability of Hg and Se in its deep-water habitat; the Se:Hg molar ratio was calculated to establish baseline information of the species and its associated ecosystem. The organisms were collected from northern Gulf of California. Hg levels in muscle were higher than liver and the opposite pattern happened with Se concentrations. Female had total lengths and weights higher than male but there were not found differences between elements concentrations by sex. Hg in muscle was correlated with weight. Molar Se:Hg ratio in muscle was the lowest compared to the liver. It was hypothesized that Hg and Se uptake to H. colliei were by its feeding habits because is a dominant species component of the demersal ecosystem and that play and important functional role in the control of oceanic ecosystem structure and function.

Bioaccumulation of mercury and selenium in tissues of the mesopelagic fish Pacific hake (Merluccius productus) from the northern Gulf of California and the risk assessment on human health.

With the aim of evaluating health risk to hake consumers, mercury and selenium were measured in muscle, liver, gonads, kidney, and gills of 62 specimens of Merluccius productus from northern Gulf of California. Means ± confidence interval (95% confidence level) concentrations (mg kg-1 wet weight) of Hg in tissues were: gonads (1.01 ± 0.25) > muscle (0.44 ± 0.06) > gills (0.29 ± 0.04) > kidneys (0.20 ± 0.07) > liver (0.02 ± 0.004). No significant differences between sexes were found for Hg. The distribution of mean concentrations of Se (mg kg-1 wet weight) were: kidneys (4.61 ± 1.27) > liver (1.66 ± 0.22) > gonads (1.66 ± 0.75) > gills (0.86 ± 0.04) > muscle (0.40 ± 0.09). Se in gonads showed a significant difference between sex (females > males). Positive significant correlations with total length (p < 0.05) and total weight (p < 0.05) were found in the same tissue for both morphological variables: Hg in muscle, Se in muscle and Se in liver. An excess of Se over Hg (molar ratio Se:Hg > 1) was found in all tissues. The Hazard Quotient health risk index was evaluated for humans that consume muscle and gonads. The recommended Hg safe intake for adults and children were 110.0 and 33.0 g week-1, respectively for muscle; for gonads weekly consumption portions of 35.0 and 14.0 g for adults and children represent no Hg risk. There was no risk of exposure to Se.

Mercury (Hg) and selenium (Se) content in the shark Mustelus henlei (Triakidae) in the northern Mexican Pacific.

Mercury and selenium were assessed in Mustelus henlei, which is a carnivorous predatory shark that is important for the coastal communities of the northern Mexican Pacific (NMP). Sixty-two individuals were sampled; muscle and liver were isolated and analyzed by atomic absorption spectrophotometry. The mean Hg concentrations (wet weight) obtained for muscle (0.08 ± 0.10 µg g-1) and liver (0.09 ± 0.26 µg g-1) were below the allowed limits (< 1.0 µg g-1 Hg). The average Se concentration was 0.03 ± 0.01 µg g-1 in muscle and 0.13 ± 0.05 µg g-1 in liver. The Se/Hg molar ratio of muscle was 1.83; however, the selenium health benefit value (HBVSe) was of 0.08. We calculated that an adult man (70 kg), an adult woman (60 kg), and a child (16 kg) could consume 1595, 838, and 223 g/week of M. henlei muscle, respectively, without risks to health. In conclusion, the concentrations and molar ratio of Hg and Se in M. henlei muscle mean that consumption of this shark's meat does not represent neither a benefit nor a public health risk.

Cadmium, mercury, and selenium in muscle of the scalloped hammerhead Sphyrna lewini from the tropical Eastern Pacific: Variation with age, molar ratios and human health risk.

With the aim of assessing health risk to shark consumers, cadmium, mercury, and selenium were measured in muscle of Sphyrna lewini from four coastal states (Baja California Sur, Sinaloa, Nayarit, and Colima) in western Mexico. According to length of specimens, three age modes were found: juveniles and neonates (the majority of the individuals), preadults and adults. Average concentrations (µg g-1 dry weight) in all the studied individuals followed the order cadmium (0.06), selenium (0.94), and mercury (1.56). The mean concentrations of cadmium and mercury increased significantly (p < 0.001) with mean length of specimens. Overall, hazard quotient and hazard index values were below one so there is no health risk to consumers. According to molar ratios of Hg and Se in the edible portion (muscle) of sharks, and depending on the areas of collection, individuals from Baja California Sur might not be beneficial to consumers.

Mercury and selenium in the filter-feeding whale shark (Rhincodon typus) from two areas of the Gulf of California, Mexico.

Mercury and selenium were measured for first time in the endangered species whale shark (Rhyncodon typus) from two areas of the Gulf of California, Bahía Los Angeles (BLA) and Bahía La Paz (LAP) using dermal biopsies of seventy specimens. Additionally, nineteen zooplankton samples from LAP were analysed. Concentrations (ng/g, wet weight (ww)) in biopsies of BLA ranged from 1 to 40 for Hg and 100 to 680 for Se; while in LAP varied from 1 to 9 for Hg and 11 to 850 for Se. A positive correlation was found for Hg in BLA males biopsies with length. Hg and Se concentrations in the zooplankton from LAP were 1.6 ±â€¯1.8 and 770 ±â€¯930 ng/g, respectively. Hg biomagnification factor ranged from 0.8 to 5.3 in sharks. A molar excess of Se over Hg was found in the biopsies and the zooplankton.

The influence of anthropogenic organic matter and nutrient inputs on the food web structure in a coastal lagoon receiving agriculture and shrimp farming effluents.

In this study, we elucidated the impacts of allochthonous organic matter (OM) and nutrients (N and P) inputs coming from agriculture and shrimp aquaculture activities on food web structure in a subtropical coastal lagoon located on the central-east of the Gulf of California. This coastal lagoon is highly influenced by OM and nutrients inputs by a large agriculture district and aquaculture development center in Mexico. We also selected a second coastal lagoon, without direct OM and nutrients inputs, considered as a 'pristine' ecosystem. We evaluated the quantity of OM, N and P in both ecosystems and reconstructed the food webs using isotopic tools of C and N from the base to top. We collected and analyzed autochthonous and allochthonous OM, and organisms including primary producers, and primary to tertiary consumers. Overall, specimens of the same species and/or functional groups showed higher δ15N values in the ecosystem receiving agriculture and shrimp aquaculture effluents than the pristine. Food webs were composed of four and five trophic levels, where fish and birds occupied the top-predator levels. Seasonal increases in OM and N and P quantities in lagoons affected by anthropogenic activities produced high δ15N values in primary producers and consumers.

Patterns of mercury and selenium in tissues and stomach contents of the dolphinfish Coryphaena hippurus from the SE Gulf of California, Mexico: Concentrations, biomagnification and dietary intake.

Selenium and mercury were evaluated in tissues and stomachs of the dolphinfish Coryphaena hippurus from two sites in the Southeastern Gulf of California. Hg levels were consistently low and exhibited the following patterns: muscle (0.14 ±â€¯0.01 µg/g wet weight) followed by kidney (0.12 ±â€¯0.02 µg/g), liver (0.11 ±â€¯0.01 µg/g), and gonads (0.04 ±â€¯0.00 µg/g). The maximum of Se was found in the kidney (5.60 ±â€¯0.40 µg/g) and the minimum in muscle (0.60 ±â€¯0.01 µg/g). All the Se:Hg molar ratios were between 3.7 and 697.1, with the minimum in muscle and the highest in gonads. The results indicate a contrasting behavior biomagnification of Hg and Se; smaller fish (<80 cm FL) did not exhibit biomagnification, in contrast with larger fish (>90 cm FL: 100% for Hg; 65% for Se). These results appear to be related to different feeding habits and availability of prey.

Mercury and selenium in tissues and stomach contents of the migratory sailfish, Istiophorus platypterus, from the Eastern Pacific: Concentration, biomagnification, and dietary intake.

Mercury and selenium were assessed in the sailfish, Istiophorus platypterus, from the Eastern Pacific. Sixty-seven individuals were sampled, muscle, liver, kidney, gonads and the prey found in the stomach contents were isolated during fishing 2011-2013 tournaments. Hg exhibited the following pattern (µg g(-1) wet weight): liver (0.57 ± 0.07)>muscle (0.56 ± 0.04)>kidney (0.44 ± 0.08)>gonad (0.14 ± 0.01). The maximum concentration of Se was found in kidneys (14.1 ± 1.9 µg g(-1)), and the minimum in muscles (0.67 ± 0.03 µg g(-1)). High Se:Hg ratios were found for muscle (4.1 ± 0.3), kidney (132.4 ± 12.1), liver (54.0 ± 4.4) and gonads (88.2 ± 7.9); Hg:Se molar ratios were several orders of magnitude lower (muscle<0.4 and liver, kidney and gonad<0.03). Sailfish feed mainly on fishes and cephalopods with low Hg levels (<0.13 µg g(-1)), these results indicate biomagnification of Hg and Se. The muscle of I. platypterus should be consumed (according the provisional tolerable weekly intake) by people cautiously so as not to exceed the recommended intake of 215 g per week.

Mercury and Selenium in Muscle and Target Organs of Scalloped Hammerhead Sharks Sphyrna lewini of the SE Gulf of California: Dietary Intake, Molar Ratios, Loads, and Human Health Risks.

Selenium and mercury were evaluated in muscle, liver, kidney, brain, and the stomach contents of juvenile scalloped hammerhead shark Sphyrna lewini. Se:Hg molar ratios were calculated. The average Hg levels in muscle ranged from 0.12 to 1.17 µg/g (wet weight); Hg was <0.39 µg/g in liver and kidneys and <0.19 µg/g in brain. The lowest value of Se was found in muscle (0.4 µg/g) and the highest in kidney (26.7 µg/g). An excess of Se over Hg was found, with Se:Hg molar ratios >1. Correlations were found for Hg in muscle with size, age, and weight, and also for Hg in liver with size, age, and weight. Hg in muscle was significantly positive correlated to Hg in brain as well as Hg in liver was correlated to Hg in kidney. The highest Hg in preys was for carangid fishes; scombrid and carangid fishes contributed with the highest Se levels. Results suggest that more than 98 % of the total Hg and 62 % of Se end up in muscle and might be affected by factors, such as geographical area, age, size, and feeding habits. The muscle of S. lewini should be consumed by people cautiously so as not to exceed the recommended intake per week.

Recent sedimentary history of organic matter and nutrient accumulation in the Ohuira Lagoon, northwestern Mexico.

(210)Pb-derived sediment accumulation rates, as well as a suite of geochemical proxies (Al, Fe, delta(13)C, delta(15)N), were used to assess the time-dependent variations of C, N, and P fluxes recorded in two sediment cores collected at Ohuira Lagoon, in the Gulf of California, Mexico, during the last 100 years. Sedimentary C, N, and P concentrations increased with time and were related to land clearing, water impoundment, and agriculture practices, such as fertilization. C:N:P ratios and delta(13)C suggested an estuarine system that is responsive to increased C loading from a N-limited phytoplankton community, whereas delta(15)N values showed the transition between an estuarine-terrestrial to an estuarine-more marine environment, as a consequence of the declining freshwater supply into the estuary due to the channeling and impoundment of El Fuerte River between 1900 and 1956. The recent increases in nutrient fluxes (2- to 9-fold the pre-anthropogenic fluxes of C and N, and 2 to 13 times for P) taking place in the mainland from the 1940s, were related to the expansion of the intensive agriculture fields and to the more recent development of shrimp farming activities.

210Pb geochronology and trace metal fluxes (Cd, Cu and Pb) in the Gulf of Tehuantepec, South Pacific of Mexico.

Distributions of Al, Cd, Cu, Fe, Li, Mn and Pb were analyzed in a sediment core collected in the Gulf of Tehuantepec, an important fisheries region located in the South Pacific of Mexico, where data on metal accumulation and accretion rates were previously almost nonexistent. Depth profiles of metal concentrations were converted to time-based profiles by using a 210Pb-derived vertical accretion rate, estimated to be 0.05 cm year(-1) on the average. Sediments were dated up to 8 cm depth, corresponding to a layer of ca. 140 years old. The historical changes of metal accumulation along the sediment core have shown a moderate enrichment of Cd, Cu and Pb concentrations at present, of about threefold the corresponding background concentrations. Chronological trace metal records showed that metal fluxes have increased over the last 20 years, reaching the maximum values at present of 2.5, 22.5 and 45.8 (microg cm(-2) year(-1)) for Cd, Pb and Cu, respectively. These increments in metal fluxes are likely influenced by the development of anthropogenic land-based activities since over this period of time oil production activities in the region have had a significant development.