Micronuclei in embryos of eight seabird species in northwestern Mexico: A biomarker of exposure to coastal pollution?

The micronucleus (MN) test may be used to evaluate genome instability in birds and the potential of different species to function as biomarkers of genotoxicity. However, little is known regarding genome instability in seabird embryos or the instability present among embryonic development stages. Therefore, the present study aimed to describe the frequencies of micronucleated erythrocytes (MNE) and micronucleated polychromatic erythrocytes (MNPCE) in blood samples collected from the embryos of eight seabird species nesting on the coast of Sinaloa, Mexico. An additional description of blood cell maturation along with embryo development during incubation was conducted based on the proportion of polychromatic erythrocytes (PCE), and the potential relationships between metals (Hg and Cd concentrations in egg content) and the MN frequencies in embryo blood were evaluated. The PCE proportion appears to decline as incubation advances (initial stage > intermediate stage > advanced stage), and the values varied between species (Suliformes/Pelecaniformes < Charadriiformes: Laridae), which may be related to differences among incubation periods and reproductive strategies. Interspecific variation in the MNPCE frequency was found in embryos showing advanced development, which could be related to both variations in life-history traits and ecological factors and not Hg or Cd exposure. The genomic instability values in this study are the first to be reported for embryos of seabird species nesting in a subtropical coastal region.

Detection of microplastic particles in scats from different colonies of California sea lions (Zalophus californianus) in the Gulf of California, Mexico: A preliminary study.

Microplastics (MPs, < 5 mm in size) are highly bioavailable to many taxa within the marine ecosystem, either ingested directly or indirectly through trophic transfer from polluted prey. The ingestion analysis of these MPs from top predators, such as pinnipeds in Mexico, is relatively unexplored. Forty-eight scats from California sea lions were collected on six rookeries along the Gulf of California. From these scat samples, 294 suspected MPs particles were classified and chemically analyzed; 34% were synthetic and semi-synthetic, and 66% were non-synthetic. Blue-colored polyethylene terephthalate fibers were the most common type of MP registered. During laboratory work, multiple contamination control measures were implemented. Although the ingestion pathway is still unknown, our results support the other authors that suggest the potential trophic transfer of MPs to top predators and incidental ingestion while foraging. The particles documented here provide important baseline information for future MP research in the Gulf of California.

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.

A comparison of pesticide residues in soils from two highly technified agricultural valleys in northwestern Mexico.

A pesticide characterization is presented for two highly technified valleys in northwest Mexico: Culiacan Valley (CV) in Sinaloa and Yaqui Valley (YV) in Sonora. Approximately 250,000 kg of active ingredients are used every year, half of which are considered highly hazardous pesticides. Legacy pesticides are still present in the soils of these valleys. The aim of the present study was to identify and quantify a wide variety of pesticides in soils and correlate their concentrations with historical and current use. Agricultural soils from both valleys were sampled and analyzed using accelerated solvent extraction and subsequent quantification by gas chromatography with selective detectors. The most frequently detected pesticides (mean, µg g-1) in CV were organochlorines (0.1967), organophosphates (0.0928), synthetic pyrethroids (0.2565), organonitrogen (0.0552), and miscellaneous pesticides (0.1851). In YV, the most frequently detected pesticides were organochlorines (0.8607), organophosphates (0.0001), synthetic pyrethroids (0.0124), and miscellaneous pesticides (0.0009). The pesticides were more diverse in CV compared to those of YV, which was based on the types of crops produced. Both locations presented highly hazardous pesticides, including concentrations above the action levels established by the Canadian Soil Quality Guide. A follow-up risk assessment is recommended to assess potential effects.

Evaluation of the genotoxic effect of heavy metals in pigeons from urban and rural habitat in Monterrey, Mexico, using the chromatin dispersion assay.

PURPOSE: Evaluate genotoxic effect of heavy metals on Pigeon Erythrocytes (PE) from urban and rural habitat (outside of the city) in Monterrey, Mexico, using the chromatin dispersion assay. MATERIALS AND METHODS: We quantified metals concentrations (Cd, Hg, Cu and Pb) in tail feathers of 22 pigeons from an urban and a rural site in northeastern Mexico. DNA damage in peripheral blood erythrocytes was measured by chromatin dispersion assay in 13 pigeon living in urban habitat and in nine living in rural habitat as the control. MicroNucleus (MN) test was used to confirm levels of DNA damage. RESULTS: Birds in urban habitat had highest concentrations in feathers for all the metallic elements analysed with respect to birds in rural habitat. Concentrations of Cu and Hg showed a significant increase (p < 0.05). Our results showed a significant increase of DNA damage in urban-habitat pigeons compared with that of pigeons in rural area. These results were confirmed by a MN test. CONCLUSIONS: Our preliminary findings demonstrate that PE examination via chromatin dispersion assay is a reliable, precise and inexpensive morphological bioassay for evaluating environmental genotoxicity associated with heavy metals. Further studies for evaluating the individual participation of contaminants in DNA damage are needed.

Synthesis of alginate-polycation capsules of different composition: characterization and their adsorption for [As(iii)] and [As(v)] from aqueous solutions.

The uptake of arsenite [As(iii)] and arsenate [As(v)] by functionalized calcium alginate (Ca-Alg) beads from aqueous solutions was investigated. Ca-Alg beads were protonated with poly-l-lysine (PLL) or polyethyleneimine (PEI) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide (EDC/NHS) or glutaraldehyde (GA) as crosslinking agents. Four types of protonated beads were prepared: Ca-Alg-EDC/NHS (PLL or PEI) and Ca-Alg-GA (PLL or PEI). Fourier transform infrared spectroscopy in total attenuated reflection mode (FTIR-ATR), analysis showed presence and increased intensity of bands corresponding to OH, NH, CH2 and CH3 groups in modifications with both polycations. In addition, thermogravimetric analysis and atomic force microscopy of all modified capsules showed an increase in thermal stability and uniformity of the capsules, respectively. Ca-Alg-EDC/NHS-PLL beads had the maximum adsorption capacity of [As(v)] (312.9 ± 4.7 µg g-1 of the alginate) at pH 7.0 and 15 minute exposure, while Ca-Alg-EDC/NHS-PEI beads had the maximum adsorption capacity of [As(iii)] (1052.1 ± 4.6 µg g-1 of alginate). However, all these EDC containing beads were degraded in the presence of citrate. Ca-Alg-GA-PEI beads removed 252.8 ± 9.7 µg of [As(v)] µg g-1 of alginate and 524.7 ± 5.3 de [As(iii)] µg g-1 of alginate, resulting the most stable capsules and suitable for As removal.

Review of California sea lion (Zalophus californianus) abundance, and population dynamics in the Gulf of California

Introduction: The life history of the California sea lion (Zalophus californianus) in the Gulf of California is marked by a series of important events influencing and modifying its population growth, distribution, and evolution. Despite the fact that this population has been studied since the 1950s, research has been rather punctual and fragmentary. Before 2010, there are only a few surveys conducted simultaneously in all rookeries, thus there is no reliable information on key aspects of life cycle, population trend and potential threats. In the present work we conducted a review of California sea lion life history and environmental changes in the Gulf of California thorough a collation survey data encompassing the last 37 years. Objective: Our aim was focused on identifying short- and long-term processes potentially acting on the population, and hopefully improve knowledge about the population trend and status using different points of view. Methods: We collected and analyzed population survey data from different sources since the 1970s to 2018: published papers, master's and doctoral thesis, in addition to technical reports. The survey data are organized in sections corresponding with crucial population life history events. Results: Considering a long-time period the population size appears to be stable with zero growth. Cyclic interannual fluctuation seem to denote a certain dependence with climatic factors, not directly with El Niño, but with sea surface temperature anomalies that determine prey availability. However, many doubts persist about the incidence of different local environmental factors on gender and age, particularly related with juvenile recruitment and female survival rate. Conclusions: In conclusion, more information is required based on seasonal surveys, life cycle, regional environmental variation. Statistical errors need to be assessed and monitoring methods should be standardized and must be considered to ascertain short- and long-term population and colony spatial-temporal patterns.

Introducción: El lobo marino de California (Zalophus californianus) en el Golfo de California se caracteriza por una serie de eventos que influyen en el crecimiento, evolución y distribución de la población. Los estudios poblacionales iniciaron en 1950, aunque las investigaciones fueron puntuales y fragmentadas. Antes de 2010 existen pocos censos simultáneos de las 13 colonias de lobos marinos, con los cuales se obtuvo información sobre el ciclo de vida, la tendencia poblacional y las potenciales amenazas de estos organismos. Objetivo: En esta investigación se presenta un resumen de 37 años de historia de investigaciones del lobo marino de California y del ecosistema del Golfo de California. Métodos: Se realizó un análisis de los procesos de corto y largo plazo que actúan sobre la población, revelando aspectos poco conocidos. Se recolectaron y analizaron datos para el periodo de 1970 al 2018: artículos, tesis de posgrado y reportes técnicos, que fueron organizados en secciones relacionadas con eventos ambientales cruciales para la población. Resultados: A largo plazo, la población parece estar estable y presenta fluctuaciones interanuales cíclicas que evidencian dependencia con factores climáticos como anomalías de temperatura superficial del mar regional que determinan un cambio en la disponibilidad de presas para los lobos marinos. No es claro el posible efecto que factores ambientales locales puedan ocasionar en las diferentes clases de edad y por sexos, en particular sobre el reclutamiento de juveniles y la tasa de supervivencia de las hembras. Conclusiones: El presente trabajo identifica las prioridades de información para esta población y ofrece recomendaciones como el monitoreo estandarizado y la consideración de variaciones espacio-temporales locales.

Mercury Concentration, DNA Methylation, and Mitochondrial DNA Damage in Olive Ridley Sea Turtle Embryos With Schistosomus Reflexus Syndrome.

Schistosomus reflexus syndrome (SR) is a rare and lethal congenital malformation that has been reported in the olive ridley sea turtle (Lepidochelys olivacea) in Mexico. Although the etiology remains unclear, it is presumed to be genetic. Since embryonic development in sea turtles largely depends on environmental conditions, we investigated whether sea turtle total mercury content participates in the etiology of SR. Given that several toxins are known to affect both DNA methylation and/or mitochondrial DNA (mtDNA) copy number, we also probed for associations of these parameters to SR and mercury exposure. We measured the levels of each variable in malformed olive ridley sea turtle embryos (either with SR or other non-SR malformations) and embryos without malformations. Malformed embryos (with or without SR) showed higher mercury concentrations compared to normal embryos, while only embryos with SR showed higher levels of methylation compared to embryos without malformations and those with other malformations. Furthermore, we uncovered a positive correlation between mercury concentrations and DNA methylation in SR embryos. With respect to mtDNA copy number, no differences were detected across experimental groups. Because of sample size limitations, this study is an initial attempt to understand the association of environmental toxins (such as mercury) and epigenetic alterations (DNA methylation) in the etiology of SR in sea turtles.

O-hexyl O-2,5-dichlorophenyl phosphoramidate as a substrate for domestic and sea bird serum A-esterases: Hydrolysis levels, Cu2+- and Zn2+-dependence and stereoselectivity.

O-Hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) induces delayed neuropathy in hens. It has been used as a tool to identify new A-esterase activities in animal tissues. This study shows the EDTA-resistant, Cu2+- and Zn2+-dependent hydrolysis of racemic HDCP in domestic and sea bird serum using UV/Vis spectrophotometry and chiral chromatography. The results clearly show a significant (p ˂ 0.05) Cu2+- and Zn2+-dependent HDCP hydrolysis in the serum of all bird species versus EDTA, except for the Zn2+-dependent HDCPase activity from Yucatecan quail serum. The ratio of Cu2+/Zn2+ hydrolysis varied between 1 and 7 (intraspecies) and 15.6 (interspecies). EDTA affected the Cu2+- and Zn2+-dependent HDCPase activity in the range of 37-95% and 40-50%, respectively. HDCP hydrolysis activated by Cu2+ was significantly (p ˂ 0.05) stereoselective (R-(+)-HDCP ˃ S-(-)-HDCP) in chicken and sea bird serum. Its R-(+)-HDCP/S-(-)-HDCP ratios were 6.8 and 1.6-2.8, respectively. EDTA-resistant and zinc-dependent HDCP hydrolysis were not stereospecific in all bird sera tested. The present ex vivo study reinforces the idea that bird sera have HDCPase activity that is sensitive to divalent metals, resistant to EDTA and possibly associated with the protein albumin.

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.

Mercury Levels and Risk Implications Through Fish Consumption on the Sinaloa Coasts (Gulf of California, Northwest Mexico).

Fish consumption is the major source of mercury to humans. Fetuses and children are the most sensitive groups of populations to the effects of mercury. Consequently, fish consumption by pregnant women, children, and women of childbearing age is of concern because of the effects of mercury exposure on human health. To assess mercury exposure in a population in northwest Mexico, the allowed daily consumption of fish (which indicates the maximum daily amount of fish that can be consumed without causing adverse noncarcinogenic effects) was calculated for the general population (GP) and fishing-related population (FRP). The studied groups for both sectors of the population were children A (3-10 years old), children B (11-15 years old), women of childbearing age (16-40 years old), and the rest of the population (men ≥16 years old, and women ≥41 years old). Mercury content in canned and frozen tuna, smoked marlin, tilapia, Pacific sierra, dolphinfish, and bullseye puffer ranged from 0.01 to 0.23 µg/g wet weight; none of the values were above the limit set by Mexico. Regarding mercury concentrations and rates of fish consumption, the GP consumes 1.7-2.7 times the allowed daily consumption, and the FRP consumes 1.6-3.9 that limit. The risk analysis showed the children A and B groups from the GP and adults of FRP to be the highest percentage of the population at risk (approximately 35%). These results highlight the need for adequate strategies that consider mercury exposure as part of public health policies associated with fish consumption in Mexico.

Mercury concentrations in seafood and the associated risk in women with high fish consumption from coastal villages of Sonora, Mexico.

Mercury concentrations in the ocean have increased considerably since the industrial revolution and will continue to increase in the next 50 years. Therefore, it is important to monitor Hg levels in fish and to evaluate the health risks in populations with high fish consumption. In the present study, a total of 238 samples of commercial fish and shellfish, were analyzed from the Central Gulf of California, Mexico. Concentrations of total Hg in fish ranged from < DL (detection limit) up to 1.22 µg g-1, with a mean of 0.15 ±â€¯0.19 µg g-1, the majority of the samples were lower than the maximum permissible level. To evaluate the risk, a total of 110 food frequency questionnaires were applied to women (16-68 years old) from 15 coastal fishing villages of Sonora. Results indicated a high seafood consumption at these communities (mean = 307 g day-1), and a high hazard risk (HQ = 6.2) due to methyl mercury ingestion. It is recommended to limit seafood consumption in pregnant women to 4 portions of fish per week, preferably of low mercury concentrations so that all the benefits of seafood consumption are obtained without the negative health effects of methyl mercury.

Persistent organic pollutants (POPs) in populations of the clam Chione californiensis in coastal lagoons of the Gulf of California.

This study examines the potential public health risk due to the massive use of organochlorine pesticides (OCs) in agriculture in the Gulf of California. Specimens of the clam Chione californiensis were collected from three coastal lagoons (Yavaros, Altata and Reforma). Sites were classified as polluted/nonpolluted based on the presence/absence of OCs as an indicator of the persistence of these pollutants; in polluted sites, the time elapsed since pesticide application (past or recent) was estimated. Screening values (SV) for protecting human health as per the U.S. Environmental Protection Agency (EPA) were used for risk assessment. OCs detected were ranked according to frequency of occurrence as follows: γ-chlordane (75%) > endrin (54%) > aldrin (48%) > heptachlor, and dichlorodiphenyl-trichloroethane (DDE) (37%) > ß-heptachlor epoxide (30%) > lindane (α-BHC, δ-BHC) and endosulphan I (≤ 6%). Specifically, OCs detected at the highest concentration were heptachlor in Yavaros (0.0168 µgg(-1)) and Altata (0.0046 µgg(-1)), and aldrin in Reforma (0.0019 µgg(-1)). ß-Heptachlor epoxide in Altata and Reforma was the only OC with a concentration exceeding the EPA Screening Value. From our results and based on the monthly consumption limit set forth by EPA, the maximum safe consumption of clams to avoid a carcinogenic risk derived from ß-heptachlor epoxide in the fishing villages of Yavaros and Altata is 4 servings per month (1 serving = 0.227 kg) by a 70-kg person. These findings suggest that concentrations of OCs and their isomers in C. californiensis populations reflect environmental persistence as well as recent inputs of OCs into coastal lagoons in the Gulf of California.

Local and interannual variations in mercury and cadmium in eggs of eight seabird species of the Sinaloa coast, México.

Mercury (Hg) and cadmium (Cd) concentrations in eggs of 8 seabird species inhabiting 5 coastal ecosystems in Sinaloa, México were determined during 2 breeding seasons (2012 and 2013): blue-footed booby (Sula nebouxii), brown booby (Sula leucogaster), double-crested cormorant (Phalacrocorax auritus), magnificent frigatebird (Fregata magnificens), brown pelican (Pelecanus occidentalis), royal tern (Thalasseus maximus), laughing gull (Leucophaeus atricilla), and Heermann's gull (Larus heermanni). The interspecific differences found in the concentrations of both metals were attributed to the diet and foraging ecology of the species. The highest Hg concentrations were detected in piscivorous species (brown pelican, 0.42 µg/g; brown booby, 0.31 µg/g; blue-footed booby, 0.26 µg/g; and double-crested cormorant, 0.23 µg/g); whereas species with more varied diets presented the highest Cd concentrations (Heermann's gull, 0.31 µg/g; laughing gull, 0.27 µg/g; and magnificent frigatebird, 0.27 µg/g). Cadmium concentrations were significantly greater in 2013 than 2012 for most species, and brown pelican and laughing gull also had higher Hg concentrations in 2013 in Santa María Bay, suggesting a relationship as a result of the changes either in oceanographic conditions or in continental runoff. Mercury concentrations in brown pelican and Cd concentrations in Heermann's gull and laughing gull were above threshold levels for adverse effects on reproduction and survival. Environ Toxicol Chem 2016;35:2330-2338. © 2016 SETAC.

Concentrations of DDE in blubber biopsies of free-ranging long-beaked common dolphin (Delphinus capensis) in the Gulf of California.

Long-beaked common dolphins (Delphinus capensis) in the Gulf of California have been exposed to persistent contaminants that originated in large agricultural areas near the coast. Live common dolphins were sampled by remote dart biopsies to determine concentrations of tDDT in blubber. Life stage and initial gender identification was determined by field observations. Gender was confirmed by genetic analysis of the skin. Concentration of tDDT in blubber was analyzed by gas chromatography. The 16 samples collected consisted of: 2 adult males, 6 adult females, and 8 juveniles. 4,4'-DDE was detected in most of the samples with 4,4'-DDD and 4,4'-DDT under detection levels. Concentrations of DDE varied from non-detectable to 87.3 µg/g lipid weight with a median of 16 µg/g lipid weight. The highest concentration was detected in an immature female. No differences were detected between gender or life stage but this could be attributed to small sample size. We recommend continued sampling of D. capensis blubber biopsies from the Gulf of California in order to relate these levels with affected in vitro biomarkers such as mixed function oxidase activity.

Isopods of the genus Ligia as potential biomonitors of trace metals from the gulf of California and pacific coast of the Baja California peninsula.

Supralittoral and high intertidal coastal zones are exposed to pollution from both marine and terrestrial sources and undergo higher deposition rates than the subtidal zone. It is therefore important to identify organisms for this section of the coastal area that can be tolerant to contaminants. The aim of this study was to determine if supralittoral isopods of the genus Ligia can be used as biomonitors, since they are abundant and widely distributed. For this purpose, concentrations of trace elements were determined in Ligia isopods in toto from 26 locations across the Gulf of California and Pacific coast of the Baja California peninsula, which were collected during the summers of 2009 and 2010. The concentrations of trace elements followed the order of; Zn≥Cu>As>Cd>Pb>Hg. Elevated concentrations of copper (up to 1010 µg/g) were detected in Ligia from Santa Rosalía (SRo), a locality where industrial mining of copper has historically occurred. Industrial and municipal sewage discharges appear to have contributed to the high concentrations of zinc (326 µg/g) and lead (144 µg/g) found in organisms from Guaymas location. The high mercury concentration in organisms from Mazatlán (M) (2.01 µg/g) was associated with a thermoelectric plant. Natural sources of metals were also detected; coastal upwelling appears to be associated with high cadmium concentrations in Ligia from Punta Baja (PB) (256 µg/g) in the Pacific coast, whereas hydrothermal vents may have contributed to high concentrations of arsenic at Ensenada (E) (61 µg/g). Our results suggest that Ligia isopods reflect the natural and anthropogenic inputs of trace metals in the environment and could potentially be used as biomonitor organisms of the intertidal rocky shores of the Gulf of California and Pacific coast.

Heavy metals in the habitat and throughout the food chain of the Neotropical otter, Lontra longicaudis, in protected Mexican wetlands.

Top predators like the Neotropical otter, Lontra longicaudis annectens, are usually considered good bioindicators of habitat quality. In this study, we evaluated heavy metal contamination (Hg(tot), Pb, Cd) in the riverine habitat, prey (crustaceans and fish), and otter feces in two Ramsar wetlands with contrasting upstream contamination discharges: Río Blanco and Río Caño Grande in Veracruz, Mexico, during the dry, the wet, and the nortes seasons. Most comparisons revealed no differences between sites while seasonal differences were repeatedly detected for all of the compartments. Higher concentrations of Pb during the dry season and of Cd during the wet season in otter feces mirrored differences detected in the most seasonally consumed prey. Compared with fecal methylmercury values reported for the European otter (0.25-0.75 mg kg(-1)) in unprotected areas, the Hg(tot) levels that we measured were lower (0.02-0.17 mg kg(-1)). However, Pb (117.87 mg kg(-1)) and Cd (9.14 mg kg(-1)) concentrations were higher (Pb, 38.15 mg kg(-1) and Cd, 4.72 mg kg(-1)) in the two Ramsar wetlands. Protected areas may shelter species, but those with water-linked diets may suffer the effect of chemicals used upstream.

Heavy metal levels in marine mollusks from areas with, or without, mining activities along the Gulf of California, Mexico.

To assess the safety for human consumption of commercially important bivalves harvested from areas with or without mining activities, we compared the levels of heavy metals in mollusks collected from different coastal environments along the Gulf of California. We sampled the mussel Mytilus edulis and the clams Laevicardium elatum and Megapitaria squalida (June 2004) and the clam Chione californiensis (November 2006). Concentrations of cadmium, lead, nickel, zinc, iron, copper, and manganese in the soft tissue of the mollusks were measured by atomic absorption spectrophotometry. Based on dry weight, the highest average concentrations of iron, copper, and cadmium were found in clams from Loreto (572, 181, and 4.66 mg/kg, respectively); that of nickel, in mussels from San Luquitas (12.2 mg/kg); that of zinc, both in mussels from San Luquitas and in clams from Golfo de Santa Clara (94.3 and 91.8 mg/kg, respectively); and those of lead and manganese in clams from the Golfo de Santa Clara (9.2 and 3.68 mg/kg, respectively). Although mollusks were taken from coastal areas of the Gulf of California, which are considered to be contaminated by mining activities, the heavy metals in the sediments apparently were in a chemical form that had low bioavailability for the bivalves feeding in those areas. The interplay of oceanographic conditions and the chemical composition of anthropogenic inputs into the environment is not well understood. Thus, these factors or their interaction could potentially result in increased concentration and bioavailability of such metals in areas without effluent generated by mining activities.

Concentration of contaminants in breeding bird eggs from the Colorado River Delta, Mexico.

Organic contaminants (organochlorine [OC], organophosphorus [OP] pesticides and polychlorinated biphenyls [PCBs]), and metals (As, Cd, Hg, Pb, and Se) are a concern to avian health in the Colorado River delta, Mexico. We determined concentrations of contaminants in eggs of three breeding species of birds from the delta (mourning doves [Zenaida macroura], burrowing owls [Athene cunicularia], and marsh wrens [Cistothorus palustris]). We collected 27 eggs of mourning doves, eight eggs of burrowing owls, and 18 eggs of marsh wrens for analyses. Polychlorinated biphenyls, OC, and OP pesticides were analyzed by gas chromatography equipped with an electron capture detector, and metals were analyzed by inductively coupled plasma mass spectrometry. The non-ortho PCB congeners (PCB 77 and 126) were found in mourning dove and burrowing owl eggs at concentrations in which hatchability can be affected. Mean selenium concentration found in marsh wren eggs (5.6 microg/g dry wt) exceeded the level of concern. Arsenic and Cd were found at higher than normal concentrations, Hg concentrations did not exceed the level of concern in any of the species, and Pb concentrations were higher in eggs of species subject to hunting. With the exception of lead, marsh wren eggs contained the highest metal concentrations.