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Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs), characterized by their high mobility and environmental persistence, bioaccumulation, and trophic transfer. Considering the highly migratory nature and longevity of the whale shark, this species can be considered as an early warning bioindicator of regional contamination from the marine environment. This work investigated the concentration of twenty OCPs in thirty whale shark skin biopsies, collected between 2014 and 2015 in Bahía La Paz (Gulf of California, Mexico). Mean detected OCP levels were 33.99 ± 105.23 ng/g dw (dry weight), and ΣChlordane, ΣDrin, and ΣHCH showed the highest concentrations. Statistically differences in mean OCP concentration were not found by sex and size. PC1 and PC2 accounted for 68.1 % and 16.1 % of the total variance, respectively. The presence of higher levels of some pesticides than their corresponding metabolites suggests recent applications related to agricultural activity in the surrounding areas of Baja California peninsula.

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Landfills are sources of soil, water, and air pollution due to the release of toxic compounds such as metals and metalloids. In both tropical and temperate environments, scavenger birds such as the Black Vulture (Coragyps atratus) that have learned to use these sites as a feeding area are probably exposed to metals, metalloids and other "persistent bioaccumulative toxic substances (PBTs)" released in open dumpsite (OD) and sanitary landfill (SL). The objective of this study is to evaluate the presence and distribution of toxic metals (Al, Sn, Hg, Cu, Pb, Cd, Cr) and As in OD and SL from urban, semi-urban and rural localities in Campeche, México, using molting feathers of C. atratus as bioindicators. A total of 125 Black Vulture primary and secondary wing feathers were collected from OD and SL. Metals were determined by voltammetry through acid digestion. The highest levels of metals occurred in landfills in urban, semi-urban, and rural localities. The elements with the highest concentrations were Al, with an average of 35.67 ± 33.51 µg g-1 from rural environments, and As, with 16.20 ± 30.06 µg g-1 from the urban localities. Mercury was the only element that had a very homogeneous distribution between the three environments we studied. In general, Pb, Hg, Cu and Cd were the elements that presented the lowest concentrations with 0.32 ± 0.35, 0.16 ± 0.22, 0.14 ± 0.31 and 0.06 ± 0.10 µg g-1, respectively regardless of any particular location or environment. Black Vultures from dumpsites are good bioindicators of what humans consume in urban, semi-urban, and rural environments. However, the conservation of vultures is of great importance since these scavenger birds perform ecosystem services by feeding on decomposing organic material.

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Coastal lagoons are ecosystems that are considered providers of a variety species of commercial value to the humans. However, they are currently threatened by a variety of anthropogenic-derived impacts, including environmental pollution by microplastics (MPs). For these reasons, it is necessary to identify suitable biomonitors for monitoring MP activities in aquatic environments and for estimating human ingestion of MPs from the consumption of commercial shellfish species. Therefore, our aims were to identify the anthropogenic activities that supply MPs into a coastal lagoon in the southern Gulf of Mexico and their variety; to determine whether oysters (Crassostrea virginica) are suitable biomonitors to perform MPs monitoring activities and to conduct an estimation of how many MPs could a human consume by the ingestion of a commercial portion of oysters harvested in this coastal lagoon. Our results noted that MP concentrations from water and sediment collected in Laguna de Terminos were 210,000 and 11.3 times higher than values reported in other protected areas worldwide. MPs chemical composition revealed that fishing and urban activities supply mainly polyethylene (21.1 %), poly (butadiene) diol (12.6 %) and polyethylene terephthalate (9.5 %). It was also determined that oysters did not reflect the spatial distribution of MPs within the study area and that a human could consume up to 806.1 MPs per 237.1 g serving of an oyster cocktail. Finally, a coastal lagoon polluted with MPs increases the risk of affecting species used for human consumption.

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Environmental contaminants with chemical origins, such as organochlorine pesticides (OCPs) have major impacts on the health of marine animals, including sea turtles, due to the bioaccumulation of those substances by transference throughout the food chain. The effects of environmental pollution on the health of marine turtles are very important for management strategies and conservation. During recent decades, the south Gulf of Mexico and the Yucatan Peninsula have suffered from increasingly frequent disturbances from continental landmasses, river systems, urban wastewater runoff, port areas, tourism, industrial activities, pesticides from agricultural use, and other pollutants, such as metals, persistent organic pollutants (POPs) and hydrocarbons (from the oil industry activities), which contaminate water and sediments and worsen the environmental quality of the marine ecosystem in this region. In this study, we assessed the concentrations of OCPs in the blood and eggs of 60 hawksbill turtles (Eretmochelys imbricata) nesting at the Punta Xen turtle camp, and their effects on the nesting population's reproductive performance: specifically, maternal transfer and embryonic development were analyzed. Hematologic characteristics, including packed cell volume, white blood cell count, red blood cell count, and haemoglobin levels, and plasma chemistry values, including creatinine, blood urea nitrogen, uric acid, triglyceride, total cholesterol and glucose, were also measured. The general health of the turtles in this study, as well as their levels of urea, serum creatinine, glucose, uric, acid, cholesterol, and triglyceride, fell within normal ranges and was similar to other normal values, which could indicate the turtles' good energy levels and body conditions for nest-building activity, with all of the turtles able to successfully come ashore to nest. All the same, the obtained results also indicate that OCPs affect the nesting and reproductive performance of the hawksbill turtles, as well as their fertility and the development of the population of eggs and reproductive performance, specifically in terms of maternal transference and embryonic development. There were significant differences in the concentrations of OCPs (ΣHCHs and ΣDienes) between maternal blood and eggs, indicating that these chemicals are transferred from nesting females to eggs and, ultimately, to hatchlings. OCPs may, therefore, have an effect on the health and reproductive performance of hawksbill turtles, both in terms of their fertility and egg development. Conservation strategies need to be species-specific, due to differences in feeding, and address the reasons for any decline, focusing on regional assessments. Thus, accurate and comparable monitoring data are necessary, which requires the standardization of monitoring protocols.

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Levels of booster biocides (Irgarol, diuron, chlorothalonil, dichlofluanid and DCOIT), organotins (TBT, DBT, MBT, TPhT, DPhT and MPhT) and antifouling paint particles (APPs) were assessed in sediments of sites under the influence of maritime activities along the coastal zone of the Yucatán Peninsula, Mexico. Imposex incidence and organotin levels were also evaluated in seven caenogastropod species. The incidence of imposex was detected in five species from sites nearby fishing harbors and marinas, including the first reports to Gemophos tinctus and Melongena bispinosa. Butyltins levels were higher than phenyltins in gastropod tissues, sediments, and APPs. Regarding booster biocides, chlorothalonil was the most frequently detected compound and DCOIT was the most abundant biocide in sediments. DCOIT levels were registered in APPs from fishing harbors and marina areas. In addition, the highest levels of TBT, Irgarol, diuron and DCOIT exceeded the threshold limits set by international sediment quality guidelines, indicating that toxic effects could be expected in some of the studied areas, thus being a potential threat to marine life. Based on such outputs, Mexico urgently needs to adopt restrictive actions aiming at conserving the rich biological heritage of the Yucatán Peninsula.

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To describe the phytoplankton species composition, spatio-temporal distribution and habitats during different seasons along the central coast of the state of Campeche, Mexico, southeastern Gulf of Mexico, eight shallow-water (ca 1 m) sites from the city of Campeche Southwest to Villamar were monitored monthly from September 2016 to June 2017 by taking water-bottle samples. Average water temperature varied between 22.2 and 30.9°C and average salinity between 26.6 and 35.0. The Kolmogorov-Smirnov test, the Bartlett's test and canonical correspondence analyses were applied. Sixteen potentially harmful microalgal species were found: five species are bloom-forming, nine are potentially toxic to humans, and two affect aquatic organisms. At all sampling sites, massive algal proliferations occurred in June (beginning of rainy season) caused by the dinoflagellates Heterocapsa sp. (2.6 × 105 cells/L) and Blixaea quinquecornis (2.0 × 104 cells/L) and from October to March (windy season) by the cyanobacterium Trichodesmium sp. (2.6 × 105 cells/L).

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Polycyclic aromatic hydrocarbons (PAHs) are petroleum components that, when dissolved in the aquatic environment, can disrupt normal animal physiological functions and negatively affect species populations. Gambusia yucatana is an endemic fish of the Yucatán Peninsula that seems to be particularly sensitive to the presence of PAHs dissolved in the water. Here, we examined PAH effects on gene expressions linked to endocrine disruption and biotransformation in this species. Specifically, we examined the expression of vitellogenin I (vtg1), vitellogenin II (vtg2), oestrogen receptor α (esr1), oestrogen receptor ß (esr2), aryl hydrocarbon receptor (AhR) and the cytochrome P4503A (CYP3A) genes. We exposed G. yucatana to different concentrations of PAHs (3.89, 9.27, 19.51 µg/L) over a period of 72 h and found changes associated with reproduction, such as increases in hepatic expression of vtg, esr, AhR and CYP3A, mainly at concentrations of 9.27 and 19.51 µg/L. Our results also indicate that benzo[a]pyrene was probably the main PAH responsible for the observed effects. The genes examined here can be used as molecular markers of endocrine-disrupting compounds, as the PAHs, present in the environment, as gene expression increases could be observed as early as after 24 h. These biomarkers can help researchers and conservationists rapidly identify the impacts of oil spills and improve mitigation before the detrimental effects of environmental stressors become irreversible.

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This study identified and determined organochloride pesticide (OCs) concentrations in hair samples from children at two elementary schools: one exposed to fumigations in agricultural fields, the other unexposed. Three concentrations of OCs levels in the hair were compared (high, medium, low), and total nuclear abnormalities in buccal cells were determined: micronuclei (MNi), condensed chromatin, karyorrhexis, pyknosis, binucleate cells, karyolysis, lobed nuclei, and apoptosis. No significant differences were found for the presence of MNi between the schoolchildren from the exposed and unexposed schools, but the prevalence of OCs in both schools was over 50%, as well as the frequencies of MNi in the children were over 58%. Findings show a significant difference between the frequency of MNi in the total sample of schoolchildren (exposed school + unexposed school) in relation to the concentration of OCs detected in their hair. The children from exposed school that showed the higher concentrations of OCs in hair had higher levels of genotoxic damage in the buccal cells; compared against children with lower concentrations of OCs. The most frequent nuclear abnormalities in the exposed children were lobed nuclei (79.4%), binucleate cells (66.66%), apoptosis (65.07), and MNi (58.7%). We determined the prevalence ratio (PR) and prevalence odds ratio (POR) for the presence of MNi in buccal cells in relation to the OCs concentrations in the hair samples. Both ratios were high for MNi [PR 3.93, 95% confidence interval (CI) 1.97-7.84, p = 0.0003; and POR 7.97, 95% CI 2.62-24.28, p = 0.0003], indicating a 7.97 times greater risk that the exposed children will present > 0.2% of MNi when OCs concentrations exceed 0.447 µg/g. These indicators may be useful biomarkers of genotoxic damage in children exposed to persistent, highly-toxic compounds. Results suggest the potential risk to which those schoolchildren are exposed on a daily basis due to fumigations in nearby agricultural fields.

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Organochlorine pesticides (OCPs) have been used for many decades, both for the control of pests in agriculture and for the control of vectors of human and animal diseases. Several recent studies have reported significant concentrations of these compounds in multiple environmental substrates due to their persistence, as well as the effect they have on ecosystem health, human health, and wildlife populations. In the present study, organochlorine pesticide residues were determined and quantified in 260 blood samples from different populations of the Virginia opossum (Didelphis virginiana) from 11 rural ex-henequen sites of the state of Yucatan, Mexico. The organochlorine groups detected, following an order of predominance and concentration, were: ΣDienes (0.0557 ppm) > ΣDDTs (0.0481 ppm) > ΣEndosulfans (0.0376 ppm) > and ΣHCHs (0.0319 ppm). The highest levels of OCPs were recorded in the opossums captured in the towns of Chicxulub and Cacalchen. In 6 of the 11 localities, the OCPs detected in the opossums showed significant differences in concentration, whereas the opossums in 4 of the 11 localities did not present this difference. The results confirm the presence and persistence of OCPs in the rural environmental of Yucatan due to both the misuse and abuse of the OCPs by rural populations. In addition, the synanthropic characteristics and abundant populations of D. virginiana in the Yucatecan region make it a good candidate to serve as a biomonitor of environmental pollution in the Yucatan Peninsula. This could aid in assessing the effects exposure to pesticides and other contaminants have on the health of the Yucatecan population, whether short, medium, or long term.

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The impact of microplastics on wildlife is a recent problem for which methods to evaluate exposure still need development. Being able to identify and quantify microplastics (particles < 5 mm) in the gastric contents of live crocodiles allows us to evaluate exposure, at both individual and population level, and also its contribution as transporter of other contaminants. The method was validated to determine and quantify microplastics in crocodile stomach contents recovered during an experiment where a known amount of this contaminant was given to crocodiles via oral administration. Through stomach flushing we were able to recover more than 80 % of the total volume of microplastic administrated to each crocodile. In summary, the method used during the experiment consists of 1) immobilization of the crocodile; 2) extraction of microplastics from stomach contents obtained through stomach flushing; 3) separation, identification and quantification of recovered microplastic fragments using microscopy and FTIR. •Low cost method that uses a small number of materials, does not take long to produce results and can easily be performed in the field or the laboratory.•Effective in extracting stomach contents (95 %).•High (>80 %) and good (>60 %) recovery efficiencies within two and four days after ingestion of microplastics by crocodiles.

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Microplastics (MPs) are part of a global problem affecting all countries including those with smaller populations. Coastal sediments are a reservoir of pollutants generated in basins. Phthalate esters (PAEs) are used as additives to make plastics stronger and more flexible. Urban ecosystems are the most susceptible to receive and transport pollutants. In this study, we determined the presence of MPs and PAEs in coastal sediments and in an urban and natural drainage system, known as the "Ria" in San Francisco de Campeche city. Plastics were detected in all samples taken from both regions, with plastics ranging in size from 0.3 to 5 mm in diameter. This indicates that they are particles of plastics, paints, and fibers, which may come from boats and nylon nets or synthetic products. The greatest abundance of MPs was detected on the coast with quantities of 1392 items/m2 (dry weight), which is double than that seen in the urban channel. As for PAEs, the highest concentrations were determined in two sites: M7A with 18.292 µg g-1 dw and PE with 21.702 µg g-1 dw, with the Ría channel being the area with the highest concentration of PAEs totaling 49.315 µg g-1 dw. The amounts of MPs detected in the sediments of the coast and the Ria vary significantly among the sites (p = 0.001) and seasons (p = 0.001), with the rainy season being the season where the greatest amount of MPs were detected. Likewise, the concentrations of ∑PAEs varied significantly among seasons (p = 0.0002) and sampling sites (p = 0.0001), with the west sub-basin being the site where the greatest concentration of PAEs was detected. A strong correlation was found between the ∑PAEs and MPs, which indicates that the conditions of the system favor the release and extended presence of PAEs on the coast.

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The karstic aquifer of Yucatan features a high permeability, therefore, all contaminants placed in the soil surface, can reach it through infiltration along with the rain water. The purpose of the present study is to determine the spatial distribution of the aromatic hydrocarbons in the underground water of Merida City. Fifty wells inside the city were sampled. The sampling took place during the dry season, from October 2007 to March 2008. Liquid-liquid Hydrocarbon extraction was performed using hexane and purification was made by previously packed chromatography columns. Regarding the occurrence of polynuclear aromatic hydrocarbon (PAHs) traces, 28 water samples (56%) contained residues of these compounds. The following PAHs presented the highest concentrations: benzo(a)anthracene y benzo(k)fluoranthene 13.26 and 7.88 µg L-1 respectively. Only three of the sampled wells showed levels above those allowed by EPA and WHO norms. The origin of these compounds is mainly pyrogenic.

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ABSTRACT Cyanobacteria inhabit hypersaline, marine and freshwater environments. Some toxic and non-toxic species can form harmful blooms. The aim of this study was to identify potentially harmful cyanobacterial species in the oyster banks of Términos Lagoon, the southeastern Gulf of Mexico. Six sample sites (up to 2-m depth) were monitored monthly from August 2012 to September 2013. Water temperature, salinity, pH, dissolved oxygen saturation (% DO), inorganic nutrients and abundance of cyanobacteria were determined. Temperature and salinity were characterized by marked seasonal differences (26.8 to 30.6 °C and 6.1 to 19.5, respectively). The pH values (ranging from 7.1 to 8.4) and the % DO (88.4 to 118.2 %) suggest a predominance of photosynthetic activity in the windy season (October-February). Elevated nutrient contents are associated with the period of increased river discharge, determined by water circulation and biogeochemical processes. Fourteen taxa were identified, of which Anabaena sp., Merismopedia sp., Oscillatoria sp. and Cylindrospermopsis cuspis produced blooms. Cyanobacterial abundances were on the order of magnitude of 106 cells L-1 in October 2012 at stations S1-S6, with an average value of 3.2x105 cells L-1 and a range of 2000 to 3.1x106 cells L-1 throughout the study period; however, they showed a remarkable absence during the windy season (October to January). Anabaena sp. and C. cuspis reached abundances of 1.9x106 and 1.3x106 cells L1, respectively. The latter caused the temporary closure of oyster Crassostrea virginica harvesting for 15 days in October 2012.

RESUMEN Las cianobacterias habitan en ambientes hipersalinos, marinos y de agua dulce. Algunas especies tóxicas y no tóxicas pueden formar florecimientos nocivos. El objetivo de este estudio fue identificar las especies de cianobacterias potencialmente nocivas en los bancos ostrícolas de laguna de Términos, sureste del Golfo de México. Seis sitios de muestreo (hasta 2 m de profundidad) fueron monitoreados mensualmente de agosto de 2012 a septiembre de 2013. Se midió la temperatura del agua, salinidad, pH, saturación de oxígeno, nutrientes inorgánicos y abundancia de cianobacterias. La temperatura y la salinidad se caracterizaron por marcadas diferencias estacionales (26,8 a 30,6 °C y 6,1 a 19,5, respectivamente). Los valores de pH (de 7,1 a 8,4) y la saturación de oxígeno disuelto (de 88,4 a 118,2 %) sugieren un predominio de la actividad fotosintética en la temporada de nortes (octubre-enero). Las concentraciones elevadas de los nutrientes están asociados al periodo de mayor descarga de los ríos, determinados por la circulación y los procesos biogeoquímicos. Se identificaron 14 taxa, de los cuales Anabaena sp., Merismopedia sp., Oscillatoria sp. y Cylindrospermopsis cuspis formaron florecimientos. Las abundancias de cianobacterias fueron del orden de magnitud de 106 células L-1 en octubre de 2012 en las estaciones S1-S6, con un valor promedio de 3.2x105 células L-1 y un rango de 2000 a 3.1x106 células L-1 a lo largo del periodo de estudio. Sin embargo, mostraron una ausencia notable durante la temporada de nortes (octubre a enero). Anabaena sp. y C. cuspis alcanzaron abundancias de 1.9x106 y 1.3x106 células L-1, respectivamente. Este último causó el cierre temporal de la colecta del ostión Crassostrea virginica durante 15 días en octubre de 2012.

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To obtain plasma biochemistry values, blood was collected for 47 nesting females of apparently healthy Eretmochelys imbricata sea turtles using sodium heparin as an anticoagulant. Blood samples were collected in April-Jun for two years (nesting season). Hematologic characteristics, including packed cell volume, white blood cell counts, red blood cell count and hemoglobin level; and plasma chemistry values, including creatinine, blood urea nitrogen, uric acid, triglyceride, total cholesterol, and glucose were measured. The data generated from this study may be useful for clinical assessment of health and disease of wild hawksbill sea turtles on nearshore habitats in the Gulf of Mexico, thus contributing to a conservation of this species.

Para obter valores da bioquímica plasmática, foram coletadas amostras de sangue durante a desova de 47 tartarugas marinhas fêmeas aparentemente saudáveis da espécie Eretmochelys imbricata, utilizando heparina sódica como anticoagulante. Amostras de sangue foram coletadas durante dois anos entre os meses de abril e junho (época de nidificação). Mediu-se os parâmetros hematológicos (incluindo hematócrito, contagem de glóbulos brancos e vermelhos e nível de hemoglobina) e os valores da bioquímica plasmática (incluindo creatinina, ureia, ácido úrico, triglicérides, colesterol total e glicose). Os dados gerados a partir deste estudo podem ser úteis para a avaliação clínica de saúde e de doença em tartarugas-de-pente em habitats próximos ao litoral no Golfo do México, contribuindo para a conservação dessa espécie.

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The use of pesticides in Mexican agriculture creates an interest in learning about the presence of these substances in different environmental matrices. Glyphosate (GLY) is an herbicide widely used in the state of Campeche, located in the Mayan zone in the western Yucatan peninsula. Despite the fact that GLY is considered a non-toxic pesticide to humans, its presence in water bodies through spillage, runoff, and leaching are a risk to human health or biota that inhabit these ecosystems. In the present study, glyphosate residues were determined in groundwater, bottled drinking water, and the urine of subsistence farmers from various localities of the Hopelchén municipality in Campeche. Determination of GLY was carried out using Enzyme-Linked Immunosorbent Assay (ELISA). The highest concentrations of GLY were observed in the groundwater (1.42 µg/L) of Ich-Ek and urine (0.47 µg/L) samples of subsistence farmers from the Francisco J. Mújica communities. The glyphosate concentrations in groundwater and bottled drinking water indicate an exposure and excessive use of glyphosate in these agricultural communities. This is one of the first studies that reports glyphosate concentration levels in human urine and bottled drinking water in México and in the groundwater in the Yucatan Peninsula as part of a prospective pilot study, to which a follow-up will be performed to monitor this trend over time.

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Data on the impact of environmental pollution on the homeostasis of sea turtles remains scarce, particularly in the Southern Gulf of Mexico. As many municipalities along the coastline of the Yucatan Peninsula do not rely on a waste treatment plant, these organisms could be particularly vulnerable. We searched for relationships between the presence of organochlorine pesticides (OCP) and the level of several oxidative and pollutant stress indicators of the hawksbill sea turtle (Eretmochelys imbricata) during the 2010 nesting season at Punta Xen (Campeche, Mexico). Of the 30 sampled sea turtles, endosulfans, aldrin related (aldrin, endrin, dieldrin, endrin ketone, endrin aldehyde) and dichlorodiphenyldichloroethylene (DDT) families were detected in 17, 21 and 26, respectively. Significant correlation existed between the size of sea turtles with the concentration of methoxychlor, cholinesterase activity in plasma and heptachlors family, and catalase activity and hexachlorohexane family. Cholinesterase activity in washed erythrocytes and lipid peroxidation were positively correlated with glutathione reductase activity. Antioxidant enzyme actions seem adequate as no lipids damages were correlated with any OCPs. Future studies are necessary to evaluate the effect of OCPs on males of the area due to the significant detection of methoxychlor, which target endocrine functioning and increases its concentration with sea turtles size.

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Persistent organic pollutants (POPs) are dispersed all over the world while polycyclic aromatic hydrocarbons (PAHs) are released into the environment from pyrogenic and petrogenic sources and are not very mobile or persistent. The aim of this study was to identify POPs and PAHs from eggs of Least and Sooty Terns nesting in two protected marine areas with different anthropogenic impacts in the southern Gulf of Mexico. ΣHCHs were higher in Terminos in 2010 and higher in Alacranes in 2011. ΣDienes and ΣDDTs were higher in 2011 in both study sites. ΣEndosulfan was higher in Terminos than in Alacranes in both years. ΣDienes, ΣDDT and ΣHeptachlor were the highest in both species both years. Acenaphtylene and Fluoranthene were higher in Terminos while Pyrene was higher in Alacranes. No differences were present within species between years. In 2011 PAHs in eggs could have reflected the BP oil spill input.

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In this study we quantified and compared bioaccumulated OCPs in target fish species Cichlasoma urophthalmus (Mayan cichlid) and Oreochromis niloticus (Nile tilapia) and sediment in two lentic systems neighboring areas with different land use (Xnoha = agricultural/Mocu = nature reserve). Fish at both sites showed the same number of pesticide compounds (17) while in sediment were 17 and 20, respectively. ∑chlordane concentrations were significantly higher in Xnoha in both fish and sediment (1.0 and 0.17 µg/g, respectively). Here higher concentrations of o,p'DDT were found in fish than in sediments, this was similarly demonstrated in Mocu but to a lesser extent. The proportion of endosulfan sulfate was lower in Xnoha (<20 %) than in Mocu (<50 %) compared to the original product. Detected concentrations of ∑DDT and chlordane exceed international permissible limits. Results indicate that OCPs were present in both aquatic systems regardless of the differences in land use.

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Organochlorine pesticides and PCB (POPs) concentrations were determined in the blood and eggs of green and hawksbill turtles. We compared concentrations between species, analyzed the relationship between turtle size and the POPs concentrations and the relationship between the concentrations in the blood of the nesting turtles and their eggs. We expected higher concentrations in the hawksbill turtle because of its higher trophic level, but concentrations were not higher in all the cases. Significant differences were found in δ-HCH blood concentrations. Lindane, heptachlor epoxide and PCB 101 concentrations were significantly higher in the hawksbill eggs. The relationship between the size of the turtles and the POP concentrations in the eggs of the hawksbills showed a negative correlation. No correlation was found between the size of the female and concentrations in the blood. In eggs, only the hawksbill turtles exhibited negative correlation in the concentration of mirex and PCB 44 and size.

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Amphibians are good models for monitoring contaminants in ecosystems because they transfer xenobiotic substances throughout trophic networks. We quantified bioaccumulated POCs by capturing and sacrificing ninety-one frogs (Charadrahyla taeniopus and Ecnomiohyla miotympanum) from four riverine forests immersed in agriculture and pasture lands in the La Antigua, Veracruz, Mexico watershed. The concentrations of ∑DDTs, ∑HCHs, ∑Endosulphans, ∑Heptachlors, ∑Drines, and ∑Chlordanes were measured by gas chromatography and compared between species, sites and seasons. In E. miotympanum the concentration of ∑HCHs was highest at 4,746.46 µg/g, while in C. taeniopus that of the ∑DDTs was highest at 2,637.10 µg/g. Concentrations of ∑Endosulphans, ∑HCHs, ∑Chlordanes and ∑Drines differed between the two species, and were always higher in E. miotympanum. In E. miotympanum the concentration of ∑Drines differed between sites, while for C. taeniopus ∑Heptachlors differed between seasons and ∑Drines among sites. These findings indicate that the two frog species even bioconcentrate POCs that are banned and may disrupt their reproduction. The effect however may vary according to the site and the frog species.

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