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Mercury (Hg) bioaccumulation in deep-sea fauna (> 200 m depth) of the northern Mexican Pacific is unknown. We measured the total Hg concentration (THg µg/g wet weight) in 18 fish species, caught between 90 and 1100 m depth, in two ecoregions of the Mexican Pacific: The Gulf of California (GC) and the western coast of Baja California (BC), in the Southern Californian Pacific. We assessed spatial (ecoregion and depth) and biological (species, tissues, trophic position, sex and size) patterns of bioaccumulation. The highest THg concentrations were observed in liver (geometric mean: 1.28 ± 2.31 µg/g, range: < Method Detection Limit (MDL)–16.17 µg/g), followed by muscle (geometric mean: 0.34 ± 0.53 µg/g, range: < MDL–6.12 µg/g) and gonad (geometric mean: 0.29 ± 0.49 µg/g, range: < MDL–2.18 µg/g). The maximum limit established for human consumption (1 µg/g wet weight) was exceeded by 7.8% of the muscle samples and 31% exceeded the protection threshold for possible harmful effects in fish (0.2 µg/g wet weight). We observed that THg concentrations tended to increase at higher trophic levels, total lengths and condition factors. Our results indicate a clear differentiation of the mercury bioaccumulation patterns between GC and BC, where GC species (200–500 m) had consistently higher liver/muscle concentration ratios than those from BC (600–1100 m). Altogether, the findings presented in this study are possible evidence of differential scenarios of environmental contamination.

La determinacion de las actividades acetilcolinesterasa (AChE) y butirilcolinesterasa (BuChE) es ampliamente utilizada en estudios de monitoreo biologico para evaluar la exposicion a compuestos anticolinesterasicos y sus efectos. No obstante, se ha observado una amplia variabilidad en los valores considerados como normales para estas actividades enzimaticas, lo que puede deberse a diversos factores. Uno de los que puede tener mas influencia es la falta de parametros preanaliticos y analiticos estandarizados. En este sentido, el objetivo de este trabajo fue conocer, con una metodologia consensuada, los intervalos de las actividades AChE y BuChE en individuos no expuestos ocupacionalmente a compuestos anticolinesterasicos en diferentes estados de la republica mexicana. Se observo que el 22 % de los laboratorios participantes reportaron valores de actividad AChE dentro del rango considerado como normal. Respecto a la actividad BuChE, el 67 % reporto valores dentro del rango para una poblacion no expuesta a compuestos anticolinesterasicos. Los resultados revelaron una importante variabilidad en los valores de las actividades AChE y BuChE, que muestran la necesidad de capacitacion continua entre los analistas y la homogeneizacion de las metodologias.

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 ± 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.

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 Rosalia (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 Mazatlan (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.

For 12- and 13-membered macrocycles in which two amide linkages are integrated in the macrocyclic ring systems, the formation of 1:1 host–guest complexes with acetic and benzoic acids has been confirmed by NMR titrations. The complex formation occurs with the formation constants of 8–27 M− 1, under competition with the dimerisation of acid molecules. Benzoic acid tends to form more stable complexes than acetic acid. The binding force is due to a pair of hydrogen bonds, Ocarboxyl–H…O = Camide and C = Ocarboxyl…H–Namide, between the carboxyl group of a guest molecule and the amide group of a host molecule. The former bond is stronger than the latter, and defines the stability of the complexes. The formation of the pair of hydrogen bonds is accompanied by the conformational conversion of the amide group from the trans-form to the cis-form. The influence of such a conversion on the internal molecular motion is observed as a slight broadening of signal width. For 12- and 13-membered macrocycles in which two am...

El presente trabajo presenta la evidencia generada por el grupo de trabajo en los últimos quince años, sobre concentraciones de contaminantes y nutrientes provenientes de drenes agrícolas que descargan en humedales y bahías de Sonora. Las investigaciones se han realizado en el valle agrícola de Mexicali con 60 puntos de muestreo, en el valle del Yaqui con 30 sitios de colecta y en costas rocosas de Sonora y Baja California con 30 puntos de colecta, se muestreo agua, sedimento y biota. Los resultados indican niveles por encima de las normas establecidas de, coliformes fecales, nutrientes, algunos metales pesados como mercurio, plomo y selenio y plaguicidas organoclorados como DDE y endosulfán. También hemos observado que drenes agrícolas que descargan en lagunas dominadas por vegetación acuática (i. e. tule), presentan concentraciones de contaminantes y nutrientes significativamente menores a sitios desprovistos de esta vegetación, siendo que ambos sistemas están expuestos a los mismos contaminantes. Por lo anterior, estamos proponiendo que se considere como una opción viable, el uso de humedales artificiales como métodos para el tratamiento de drenes agrícolas en las zonas afectadas. Esta metodología ha probado ser eficiente para la remoción de nutrientes, DBO y sólidos suspendidos totales, en otros países y en el Instituto Mexicano de Tecnología del Agua, ya cuenta con casos de éxito utilizando humedales artificiales para el tratamiento de aguas residuales urbanas, por lo tanto, urgimos a la comunidad científica y gobierno de nuestro país a que se impulse esta tecnología en los drenes agrícolas de Sonora.