RESUMO
Given their predatory characteristics, long life, and high trophic levels, sharks can have a remarkable ability to bioaccumulate and/or biomagnify trace elements (TE). In the present study, 13 TE (Hg, Pb, Cd, Cu, As, Se, Zn, Cr, V, Fe, Ni, Co, and Mn) were analyzed in the muscle tissue of three shark species (Prionace glauca, Carcharhinus falciformis, and Alopias pelagicus) using high-resolution mass spectrometry inductively coupled to a plasma generator (HR-ICP-MS); 30 shark specimens of each specie were obtained during commercial fish landings in the port of Manzanillo, Mexico. The morphometric characteristics and sex of the sharks were recorded. Shark A. pelagicus accumulated higher concentrations of TE, especially for Hg and Cd, than the other species. Significant differences in the TE levels were detected between sexes in P. glauca and A. pelagicus; in all cases, the highest concentrations were found in female muscle tissue. The ability of sharks to bioaccumulate ETs depends of the metals (essentials higher than non-essential) but is explained mainly by feeding habits associated to sexes (population segregation) and size (ontogeny). The association between TE in shark specimens was related to the essentiality, their antagonistic action, and origin. The Se/Hg ratio was significantly higher than 1, evidence of the protective role of dietary Se against Hg uptake and toxicity in all specimens of the three shark species. Also, the elevate inverse correlation of As and Cd versus Se could indicate a protective action of Se against these toxic metals, but the mechanism must be investigated.
Assuntos
Tubarões , Oligoelementos , Poluentes Químicos da Água , Animais , Monitoramento Ambiental , Feminino , México , Músculos/química , Poluentes Químicos da Água/análiseRESUMO
Microbial communities play a central role in the N cycle of oceanic oxygen minimum zones (OMZs), such as in the Eastern Tropical North Pacific (ETNP). We explored the spatial distribution of the genetic potential for ammonia oxidation (amoA gene for bacteria and archaea), denitrification (nirS and nirK), anaerobic ammonium oxidation (anammox) (hzo) and dissimilarity nitrate reduction to ammonia (DNRA) (nrfA) and their relationships with the hydrological variables and isotopic composition of nitrate in the ETNP off Mexico. Oxygen concentration, the availability of N chemical forms and the upwelling shaped the distribution of N cycling genes along the water column. The high abundance of N genes and the isotopic composition of nitrate suggest the N cycling is very dynamic in the OMZ core. The accumulation of nitrite, the high abundance of archaeal amoA genes, and the deviation of the N and O isotopes of nitrate from the expected 1:1 ratio for nitrate reduction in the upper portion of this OMZ indicate that nitrification is a relevant process that fuels the denitrifier community. Conversely, the high abundances of nitrate, ammonium and nrfA genes in the deeper layer indicate that DNRA is a crucial process enhancing anammox there. These results show the need for more detailed studies of the N processes in OMZs.
Assuntos
Archaea/metabolismo , Bactérias/metabolismo , Nitrogênio/metabolismo , Oxigênio/metabolismo , Água do Mar/microbiologia , Compostos de Amônio/metabolismo , Archaea/classificação , Archaea/genética , Bactérias/classificação , Bactérias/genética , Desnitrificação , México , Microbiota , Nitratos/metabolismo , Nitrificação , Nitritos/metabolismo , Oceanos e Mares , OxirreduçãoRESUMO
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¯930â¯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.
Assuntos
Mercúrio/metabolismo , Selênio/metabolismo , Tubarões/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Espécies em Perigo de Extinção , Feminino , Masculino , Mercúrio/análise , México , Selênio/análise , Poluentes Químicos da Água/análise , Zooplâncton/química , Zooplâncton/metabolismoRESUMO
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.
Assuntos
Agricultura , Aquicultura , Monitoramento Ambiental , Poluentes Químicos da Água/análise , Animais , California , Crustáceos , Ecossistema , Cadeia Alimentar , México , Nitrogênio/análise , Fósforo/análiseRESUMO
Litopenaeus vannamei juveniles were exposed to sublethal levels (2.33-18.03 µg/L) of inorganic mercury. Time of exposure (0, 24 and 168 h) was a source of DNA damage. Mean comet tail length not changed significantly with mercury concentrations and exposure time, and this parameter cannot be used to assess DNA damage in this shrimp. Total hemocyte count showed a trend to decrease according to the increase of mercury concentrations, although no significant difference between treatments with mercury was observed. The phenoloxidase (PO) activity was not influenced by the time of exposure. At the end of the experiment, the PO in organisms exposed to 18.03 µg/L was different from the control. The time of exposure has a more important influence in superoxide dismutase than the concentration of mercury. According to these results, a suitable criterion of water quality for long-term exposure of L. vannamei should be lower than 2 µg/L of mercury.
Assuntos
Dano ao DNA , Mercúrio/toxicidade , Penaeidae/imunologia , Animais , Relação Dose-Resposta a Droga , Hemócitos/efeitos dos fármacos , Imunidade Inata , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismoRESUMO
White shrimp, Litopenaeus vannamei, subadults were exposed to four dilutions of the 96 h cadmium LC50 reported for postlarvae (PL12) of this species, and the effects were evaluated after 5, 48, and 96 h of exposure. While treatments did not affect survival and hemolymph clotting time increased with time, but not as a response to Cd exposure, the intensity of other responses was related to concentration, to time of exposure, and to their interaction. Hemocyanin decreased with time in all metal concentrations but increased in the control treatment, and an almost similar trend was observed with hemocyte numbers. As an initial response, phenoloxidase activity decreased with all metal concentrations, but it increased later to values similar or higher than the control treatment.
Assuntos
Cádmio/toxicidade , Hemócitos/efeitos dos fármacos , Hemolinfa/efeitos dos fármacos , Penaeidae/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Hemocianinas/metabolismo , Hemócitos/metabolismo , Hemolinfa/metabolismo , Monofenol Mono-Oxigenase/metabolismo , Penaeidae/metabolismoRESUMO
Lead concentrations and isotopic compositions in blood samples of 34 children (ages 2-17 years) living within a 113 km(2) area of a silver-zinc-lead smelter plant in Torreón, México were compared to those of associated environmental samples (soil, aerosols, and outdoor and indoor dust) to identify the principal source(s) of environmental and human lead contamination in the area. Lead concentrations of soil and outdoor dust ranged 130-12,050 and 150-14,365 µg g(-1), respectively. Concentrations were greatest near the smelter, with the highest levels corresponding with the prevailing wind direction, and orders of magnitude above background concentrations of 7.3-33.3 µg g(-1). Atmospheric lead depositions in the city varied between 130 and 1350 µg m(-2) d(-1), again with highest rates <1 km from the smelter. Blood lead (PbB) concentrations (11.0±5.3 µg dl(-1)) levels in the children ranged 5.0-25.8 µg dl(-1), which is 3-14 times higher than the current average (1.9 µg dl(-1)) of children (ages 1-5 years) in the US. Lead isotopic ratios ((206)Pb/(207)Pb, (208)Pb/(207)Pb) of the urban dust and soil (1.200±0.009, 2.467±0.003), aerosols (1.200±0.002, 2.466±0.002), and PbB (1.199±0.001, 2.468±0.002) were indistinguishable from each other, as well as those of the lead ores processed at the smelter (1.199±0.007, 2.473±0.007). Consequently, an elevated PbB concentrations of the children in Torreón, as well as in their environment, are still dominated by industrial emissions from the smelter located within the city, in spite of new controls on atmospheric releases from the facility.
Assuntos
Exposição Ambiental/estatística & dados numéricos , Poluentes Ambientais/sangue , Intoxicação por Chumbo/epidemiologia , Chumbo/sangue , Metalurgia/estatística & dados numéricos , Adolescente , Aerossóis/análise , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Criança , Pré-Escolar , Estudos de Coortes , Poeira/análise , Poluentes Ambientais/análise , Feminino , Humanos , Resíduos Industriais/análise , Resíduos Industriais/estatística & dados numéricos , Chumbo/análise , Intoxicação por Chumbo/sangue , Masculino , México/epidemiologia , Solo/químicaRESUMO
Trace metals (Cd, Cu, Ni, and Zn) concentrations were assessed in the sea turtle Lepidochelys olivacea from a nesting colony of Oaxaca, Mexico. Twenty-five female turtles were sampled, a total of 250 eggs were collected during the "arribada" event of the 2005-2006 season. Zn concentrations were highest in the yolk [72.3 ± 10.9 µg/g dry weight (dw)] and blood (58.4 ± 4.7 µg/g dw), whereas Ni concentrations were highest in the shell (48.5 ± 12.9 µg/g dw). The mean concentrations of Cu, and Cd in the analyzed tissues were lower than those reported in other sea turtle species. However, Zn and Ni concentrations in the yolk and shell, respectively, had the same distribution pattern observed at loggerhead and green turtles. On the basis of one nesting season, the maternal transfer and/or the excretion rates of trace metals via eggs-laying, estimated in terms of metal burdens in whole body, were 0.2, 7.8, 3.4, and 21.5% for Cd, Cu, Zn, and Ni, respectively.
Assuntos
Monitoramento Ambiental , Metais Pesados/sangue , Óvulo/metabolismo , Tartarugas/sangue , Poluentes Químicos da Água/sangue , Animais , Exposição Ambiental/análise , Exposição Ambiental/estatística & dados numéricos , Feminino , Metais Pesados/metabolismo , Medição de Risco , Tartarugas/metabolismo , Poluentes Químicos da Água/metabolismo , Poluição Química da Água/análiseRESUMO
Macroalgae blooms of Gracilaria vermiculophylla, Hypnea spinella and Spyridia filamentosa have been found in coastal lagoons in the SE Gulf of California. Agriculture, livestock, shrimp and poultry farms and sewage contribute anthropogenic nitrogen to the systems. The delta(15)N of these sources, water column and macroalgae were studied in order to identify the N supply for macroalgae blooms. delta(15)N of three species of macroalgae (4.3-13.6 per thousand) were enriched compared to the water column (delta(15)N-NO(3)(-) 3.7-6.8 per thousand), probably because of fractioning from the macroalgae. delta(15)N of POM (1.4-10.3 per thousand) was similar to the water column but the relationship was unclear. Depending on the site, macroalgae showed different delta(15)N values since some sites receive more or less influence from one given source of the associated watershed, which is reflected in the different delta(15)N values of the macroalgae of the same system and in the relative contributions of the sources.
Assuntos
Agricultura , Aquicultura , Eucariotos/química , Eucariotos/crescimento & desenvolvimento , Eutrofização/fisiologia , Isótopos de Nitrogênio/análise , México , Oceanos e Mares , Água do Mar/química , EsgotosRESUMO
Lead pollution was investigated in environmental matrices and biological indicators collected from two typical subtropical coastal ecosystems in the southeast Gulf of California, Mexico. Lead concentrations and isotopic compositions ((206)Pb/(207)Pb and (208)Pb/(207)Pb) were measured using high resolution inductively-coupled plasma-mass spectrometry (HR-ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. Lead in surface estuary sediments (10.0-34.2microgg(-1)) and particulate Pb (25.0-128.7microgg(-1), >98% of total Pb) in the water column were significantly higher than levels in natural bedrock soils (15.1+/-8.3microgg(-1)) and river runoff (1.9+/-1.4microgg(-1)). Aquatic plants had Pb concentrations between 2.5 and 7.2microgg(-1), while those in macroalgae ranged from 3 to 5microgg(-1). The ranges of mean Pb concentrations in the aquatic animals studied (ranges in microgg(-1)) were as follows: zooplankton 32+/-3, mussels 2.3-3.9, oysters 1.9-7.9, snail 2.0-7.7, barnacles 0.1-18.5, fish 1.4-8.9, crab 6.3-40.2 and polychaetae 8.5-16.7. Pb values in 20-40% of oyster and fish samples and in all samples of crab exceeded acceptable levels for a food source for human consumption. Pb isotope ratios (206)Pb/(207)Pb, (208)Pb/(207)Pb in biota ranged from 1.188 to 1.206 and 2.448 to 2.470, respectively. A plot of (206)Pb/(207)Pb versus (208)Pb/(207)Pb for the environmental and biological samples collected from two study areas indicates that they contain lead from ores mined in Mexico and used in the past to produce leaded gasoline in use until 1997, natural Pb weathered from the Sierra Madre Occidental mother rock, and the later influence of inputs from a more radiogenic source related to industrial activity in the United States. Statistical software IsoSource results revealed that the Pb contained in environmental matrices and biomonitors is mostly derived from gasoline (20-90%) and US emissions (10-40%).
Assuntos
Ecossistema , Monitoramento Ambiental , Chumbo/análise , Poluentes Químicos da Água/análise , Animais , Eucariotos/química , Sedimentos Geológicos/química , Isótopos/química , México , Rhizophoraceae/química , Água do Mar/químicaRESUMO
This work evaluates current metal concentrations (Cd, Cu, Pb and Zn) and the operational bio-available chemical extraction fraction in surface sediments in Mazatlán Harbor in Northwest México. Sediment samples were also analyzed for organic carbon, carbonates and particle size. Ranges of bulk metal were as follows: Cd from 3.1 to 3.3 microg/g, Cu from 31.9 to 44.9 microg/g, Pb from 49.6 to 54.0 microg/g, and Zn from 217.8 to 323.5 microg/g. In terms of biological effects, metals concentrations in the sediments lie between the low and median ranges of the mean quality guideline criteria. Comparatively, the metals concentrations increased from 1983 to 1994 and then for 2006, except Pb and Cd that decreased in the last period of time. The bio-available fraction of metals increased from 1983 to 1994, but only bio-available Cu increased from 1994 to 2006, due to mobilization of this metal from the organic matter-sulfide phase.
Assuntos
Sedimentos Geológicos/química , Metais Pesados/análise , Poluentes Químicos da Água/análise , Cádmio/análise , Cobre/análise , Chumbo/análise , Zinco/análiseRESUMO
Analyses of lead isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of dated sediment cores from two coastal estuaries and two inland lakes chronicle the predominance of industrial lead emissions in Mexico over the past century. These isotopic ratios exhibit a shift in composition from the turn of the previous century (1900) that corresponds with measurable increases (from 2- to 10-fold) in lead concentrations in the cores above their baseline values (3-22 microg/g)--both changes are consistent with the development of Mexican lead production for export and the manufacture of tetraethyl lead additives for Mexican gasolines. While subsequent changes in lead concentrations in the cores correspond with calculated emissions from the combustion of leaded gasoline in Mexico, isotopic compositions of the cores remain relatively constant throughout most of the 1900s (e.g., 206Pb/207Pb = 1.200 +/- 0.003; 208Pb/207Pb = 2.463 +/- 0.004). That isotopic constancy is attributed to the widespread pollution from lead production in Mexico and the dispersion of some of that lead used as an additive in Mexican gasolines.