RESUMEN
Trace metals concentrations along with stable isotopes ratios were measured in marine algae, sea grass, sponges, echinoderms, mollusks, crustaceans, fishes, and the California sea lion, to assess the bioaccumulation potential and detect potential risks for top predators off Bahia Magdalena, Mexico. We assessed the trophic magnification factor (TMF) to determine the potential for biomagnification of 11 trace metals. The concentrations of Fe and Zn were one order of magnitude higher than all other metals. Concentrations of As, Cu, Cd, Co, Cr, Fe, Mn and Ni correlated negatively with trophic level, supporting trophic dilution (TMF < 1, p > 0.05), while Zn and Hg had significant trophic magnification (TMF > 1, p < 0.05) when assessing only the benthic-pelagic foodweb. This research provides a baseline concentration of metals in multiple species, metal-specific foodweb bioaccumulation and biomagnification of mercury, underscoring the key role of the macrobenthic community as biovectors for trophic transfer of Hg through the foodweb to the California sea lion.
Asunto(s)
Mercurio , Leones Marinos , Oligoelementos , Contaminantes Químicos del Agua , Animales , Bioacumulación , México , Brasil , Cadena Alimentaria , Metales/análisis , Mercurio/análisis , Oligoelementos/análisis , Peces , Contaminantes Químicos del Agua/análisis , Monitoreo del AmbienteRESUMEN
Trace element (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, As, Hg) concentrations were assessed in marine organisms (n = 52) sampled from the Magdalena Bay lagoon complex in Baja California Sur, Mexico, a pristine marine environment. The overall trend of metal concentrations (dry weight) in the organisms was found to be Fe > Zn > Cd > Cu > Mn > Pb > As > Hg > Ni > Cr > Co. Bivalve mollusks (53.83 mg kg-1) contained twofold higher levels of metals than the finfishes (20.77 mg kg-1). Calculated BioConcentration Factor (BCF) values showed that dissolved Mn is readily bioavailable to the organisms, whereas Biota Sediment Accumulation Factor (BSAF) indicated high values for Zn, Cu and Cd. Cd and As levels were observed to be increasing with the trophic levels. Toxic elements, namely Pb, Cd and As in the studied fish species were found to be higher than the values recommended for human seafood consumption. The study provides a comprehensive baseline report on trace element bioaccumulation in several marine organisms that will aid in developing effective conservation strategies of the highly biodiverse lagoon complex.
Asunto(s)
Peces , Metales/análisis , Contaminantes Químicos del Agua/análisis , Animales , Organismos Acuáticos , Bahías , Crustáceos/química , Monitoreo del Ambiente , Cadena Alimentaria , Contaminación de Alimentos/análisis , Mercurio/análisis , México , Moluscos/química , Océano PacíficoRESUMEN
Pinniped vibrissae provide information on changes in diet at seasonal and annual scales; however, species-specific growth patterns must first be determined in order to interpret these data. In this study, a simple linear model was used to estimate the growth rate of vibrissae from adult female California sea lions (Zalophus californianus) from San Esteban Island in the Gulf of California, Mexico. The δ15N and δ13C values do not display a marked oscillatory pattern that would permit direct determination of the time period contained in each vibrissa; thus, time (age) was calculated in two ways: 1) based on the correlation between the observed number of peaks (Fourier series) in the δ15N profile and the length of each vibrissa, and 2) through direct comparison with the observed number of peaks in the δ15N profile. Cross-correlation confirmed that the two peaks in the δ15N profile reflected the two peaks in the chlorophyll-a concentration recorded annually around the island. The mean growth rate obtained from the correlation was 0.08 ± 0.01 mm d-1, while that calculated based on the observed number of peaks was 0.10 ± 0.05 mm d-1. Both are consistent with the rates reported for adult females of other otariid species (0.07 to 0.11 mm d-1). Vibrissa growth rates vary by individual, age, sex, and species; moreover, small differences in the growth rate can result in significant differences over the time periods represented by the isotopic signal. Thus, it is important to assess this parameter on a species-by-species basis.
Asunto(s)
Isótopos de Carbono/química , Isótopos de Nitrógeno/química , Leones Marinos/fisiología , Animales , California , Dieta , Femenino , Islas , MéxicoRESUMEN
Concentrations of 11 trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, As, Hg) in 40 fish species from Santa Maria Bay, Baja California Sur, Mexico, the strategically important area for marine mammals and organisms were analyzed. Based on their concentrations the ranking of metals Fe>Zn>Ni>Cr>Mn>Pb>Cu>Co>As>Cd>Hg suggests that organism size, metabolism and feeding habits are correlated with metal concentrations. Local geological formations affect the concentrations of different metals in the aquatic environment and are subsequently transferred to fishes. The correlation analysis suggests that metabolism and nurturing habits impact the concentration of metals. Concentrations of Fe and Mn appear to be influenced by scavenging and absorption processes, which vary by species. The considerable variability in the metal concentrations obtained in different species underscores the importance of regular monitoring.
Asunto(s)
Peces/metabolismo , Metales Pesados/metabolismo , Contaminantes Químicos del Agua/metabolismo , Animales , Bahías , Monitoreo del Ambiente , Metales Pesados/análisis , México , Contaminantes Químicos del Agua/análisisRESUMEN
Infections with Brucella ceti and pinnipedialis are prevalent in marine mammals worldwide. A total of 22 California sea lions (Zalophus californianus) were examined to determine their exposure to Brucella spp. at San Esteban Island in the Gulf of California, Mexico, in June and July 2011. Although samples of blood, vaginal mucus and milk cultured negative for these bacteria, the application of rose Bengal, agar gel immunodiffusion, PCR and modified fluorescence polarization assays found that five animals (22.7%) had evidence of exposure to Brucella strains. The data also suggested that in two of these five sea lions the strains involved were of terrestrial origin, a novel finding in marine mammals. Further work will be required to validate and determine the epidemiological significance of this finding.
Asunto(s)
Brucella/clasificación , Brucelosis/veterinaria , Leones Marinos , Animales , Técnicas Bacteriológicas , Brucelosis/microbiología , Femenino , México , Leche/microbiología , Moco/microbiología , Océano Pacífico , Vagina/microbiologíaRESUMEN
RATIONALE: Tissues with different turnover rates have different isotope compositions and reflect the different periods in an animal's life when the isotopes are incorporated during the growth of tissues. Bone is one of the most used tissues for reconstruction of an animal's diet; however, the time of isotope integration remains unknown for many species. METHODS: The δ(15)N and δ(13)C values in tooth dentine and bone tissue from the maxilla and mandible of 21 stranded northern elephant seals, Mirounga angustirostris, collected on the San Benito and Magdalena Islands, Mexico, between 2000 and 2008 were compared. Bone and dentine samples from each growth layer within the tooth were analyzed using a PDZ Europa ANCA-GSL elemental analyzer interfaced with a PDZ Europa 20-20 continuous flow gas source mass spectrometer. RESULTS: The δ(15)N and δ(13)C values were not different between bone structures, indicating similar turnover rates, metabolic activity and amino acid compositions. The differences in the observed δ(13)C values between tissues are probably indicative of differences in their amino acid compositions, although the similarities in δ(15)N values indicated less variation from different amino acids. Correlation of the analyses between isotopic values of tissues suggests that the maxilla and/or mandible of M. angustirostris might reflect the δ(15) N signal incorporated during the last 5 years of life of the individuals. CONCLUSIONS: This study demonstrated the usefulness of the applied approach for providing a best approximation of the timing of isotopic integration into the skull of a marine mammal, thereby reducing uncertainty in exploring historic changes in the species' feeding behavior.
Asunto(s)
Mandíbula/química , Maxilar/química , Phocidae/metabolismo , Diente/química , Animales , Isótopos de Carbono/análisis , Espectrometría de Masas , Isótopos de Nitrógeno/análisis , Phocidae/anatomía & histologíaRESUMEN
Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were measured in muscle-blubber biopsy samples from 21 Galapagos sea lion (Zalophus wollebaeki) pups that were live captured in the Galapagos Islands (Ecuador) using gas chromatography/high-resolution mass spectrometry. Only traces of PBDEs were detected in one male pup, whereas PCDDs and PCDFs were not detected in any sample. The total concentration of PCBs (ΣPCB) in the pups averaged 104 µg/kg lipid (range, 49-384 µg/kg). No statistically significant differences in ΣPCB were observed among the four study sites in the Galapagos Islands. Concentrations of PCB congeners in Galapagos sea lion pups were dominated by low-molecular-weight congeners. These results suggest that global transport is the main source for PCBs in Galapagos sea lions. The ΣPCB levels were below immunotoxic and endocrine-disruption thresholds in pinnipeds, suggesting a limited risk of adverse health effects. The present study indicates that Galapagos sea lions can serve as a useful sentinel of pollutants with a long-range transport capacity and that Galapagos Islands are not exempt from the threats of global pollutants despite its remote locale.
Asunto(s)
Benzofuranos/análisis , Dioxinas/análisis , Éteres Difenilos Halogenados/análisis , Bifenilos Policlorados/análisis , Leones Marinos/metabolismo , Contaminantes Químicos del Agua/análisis , Animales , Benzofuranos/toxicidad , Dibenzofuranos Policlorados , Dioxinas/toxicidad , Ecuador , Monitoreo del Ambiente/métodos , Femenino , Cromatografía de Gases y Espectrometría de Masas , Éteres Difenilos Halogenados/toxicidad , Masculino , Bifenilos Policlorados/toxicidad , Control de Calidad , Análisis de Regresión , Medición de Riesgo , Contaminantes Químicos del Agua/toxicidadRESUMEN
A pressing need exists to develop new approaches for obtaining information on demographic rates without causing further threats to imperiled animal populations. In this paper, we illustrate and apply a data-fitting technique based on quadratic programming that uses stage-specific abundance data to estimate demographic rates and asymptotic population growth rates (lambda). We used data from seven breeding colonies of California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Estimates of lambda were similar to those from previous studies relying on a diffusion approximation using trends in total abundance. On average, predicted abundances were within 24% of the observed value for the inverse estimation method and within 29% of the observed value for the diffusion approximation. Our results suggest that three of the seven populations are declining (lambda < 1), but as many as six may be at risk. Elasticity and sensitivity analyses suggest that population management in most sites should focus on the protection of adults, whose survival generally contributes the most to lambda. The quadratic programming approach is a promising noninvasive technique for estimating demographic rates and assessing the viability of populations of imperiled species.
Asunto(s)
Leones Marinos , Animales , México , Densidad de Población , Sensibilidad y EspecificidadRESUMEN
The levels of six trace metals (Hg, Se, Pb, Cu, Fe, and Zn) were measured in the hair of California sea lion pups from eight rookeries in the Gulf of California, with the aim of relating these levels with the animals feeding habits, trophic level, and delta(15)N signatures at each locality. Trace metal levels were seen to vary significantly between sample sites as were tendencies associated with feeding habits. Mercury concentrations showed a clear positive correlation with trophic level (r = 0.73, p = 0.06) as well as the delta(15)N values of the rookeries (r = 0.79, p = 0.033). This was explainable via the process of biomagnification, although other elements did not follow the same tendency. High Cu concentrations in the hair (18 and 47 microg g(-1); ANOVA, p < 0.05) were observed at San Pedro Mártir and San Esteban, where the consumption of squid is higher than at other localities (approximately 17% and approximately 27% of the diet, respectively). Se and Hg concentrations correlated positively (r = 0.73, p = 0.038), probably the result of detoxification processes, a phenomenon previously reported in marine mammals. In light of the high degree of philopatry among sea lions in the Gulf and their pups' dependence exclusively upon their mother's milk during the first months of life, the analysis of trace metals in the easily sampled hair of the pups, offers an indirect way of monitoring the toxicology of the sea lion populations.
Asunto(s)
Conducta Alimentaria , Cabello/química , Leones Marinos/metabolismo , Oligoelementos/análisis , Animales , Cobre/análisis , Hierro/análisis , Plomo/análisis , Mercurio/análisis , Selenio/análisis , Zinc/análisisRESUMEN
Commercial and subsistence fisheries pressure is increasing in the Gulf of California, Mexico. One consequence often associated with high levels of fishing pressure is an increase in bycatch of marine mammals and birds. Fisheries bycatch has contributed to declines in several pinniped species and may be affecting the California sea lion (Zalophus californianus) population in the Gulf of California. We used data on fisheries and sea lion entanglement in gill nets to estimate current fishing pressure and fishing rates under which viable sea lion populations could be sustained at 11 breeding sites in the Gulf of California. We used 3 models to estimate sustainable bycatch rates: a simple population-growth model, a demographic model, and an estimate of the potential biological removal. All models were based on life history and census data collected for sea lions in the Gulf of California. We estimated the current level of fishing pressure and the acceptable level of fishing required to maintain viable sea lion populations as the number of fishing days (1 fisher/boat setting and retrieving 1 day's worth of nets) per year. Estimates of current fishing pressure ranged from 101 (0-405) fishing days around the Los Machos breeding site to 1887 (842-3140) around the Los Islotes rookery. To maintain viable sea lion populations at each site, the current level of fishing permissible could be augmented at some sites and should be reduced at other sites. For example, the area around San Esteban could support up to 1428 (935-2337) additional fishing days, whereas fishing around Lobos should be reduced by at least 165 days (107-268). Our results provide conservation practitioners with site-specific guidelines for maintaining sustainable sea lion populations and provide a method to estimate fishing pressure and sustainable bycatch rates that could be used for other marine mammals and birds.
Asunto(s)
Conservación de los Recursos Naturales , Leones Marinos/fisiología , Animales , Ecosistema , Explotaciones Pesqueras , México , Modelos Biológicos , Dinámica Poblacional , ReproducciónRESUMEN
No hay duda de que el hombre ha provocado cantidad de extinciones, sobre todo en el medio terrestre. En el mar, en cambio, comprobar más allá de la duda razonable que el último representante de una especie ha desaparecido de la faz de la tierra es una tarea más difícil. En el presente trabajo se muestran los resultados más importantes de una rigurosa revisión de las extinciones marinas documentadas durante los últimos 200 años. Se encontró que ~50 por ciento de las extinciones y extirpaciones de especies marinas resultan dudosas porque no se considera información crítica acerca de su distribución espacio-temporal, o bien la evidencia que se utiliza para evaluarlas es insuficiente o inadecuada. Se concluye que 1) el hombre es capaz de eliminar especies marinas, en particular aquellas que naturalmente son más propensas a la extinción; 2) las extinciones registradas en el mar son menos frecuentes que las del medio terrestre, y a pesar de que existe una tendencia positiva en el número promedio de extinciones documentadas durante los siglos XIX y XX, la tendencia de las extinciones registradas es negativa en los últimos 100 años; 3) antes de declarar una especie como extinta, la evidencia que apoya tal declaración debe ser evaluada con todo el rigor científico; y 4) declarar de manera prematura la extinción de especies, pudiera afectar negativamente los propios esfuerzos que se inviertan para la conservación.