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Atmospheric concentrations of BTEX were measured in an urban site located in the vicinity of an oil storage-distribution facility in Paraiso, Tabasco, Mexico. Samples were collected during two seasons (nortes 2018 and dry 2019). The relative abundance of BTEX mean concentrations was: toluene (5.24 µg m−3) > ethylbenzene (3.92 µg m−3) > m, p-xylene (3.89 µg m−3) > benzene (2.43 µg m−3). BTEX concentrations had a clear diurnal and seasonal pattern, showing higher levels during the dry season due to differences in wind conditions, rainfall patterns and temperature. Statistical analysis showed significant positive correlations among BTEX, indicating that these compounds had common sources. Interspecies ratios revealed that BTEX were originated from sources beyond vehicular traffic and that they were influenced by the transport of local air masses. The assessment of lifetime cancer risk showed that the population in the study area is at possible risk of developing cancer.

The purpose of this study was to study the spatial and temporal variation of BTEX in the ambient air of Leon, Guanajuato, Mexico, to assess the inhalation health risk to the local population from exposure to these compounds. BTEX were monitored using passive samplers during two sampling seasons (rainy 2019 and cold dry 2020), and samples were analyzed by gas chromatography with flame ionization detection. BTEX ratios and meteorological analysis suggested that the concentrations were mainly influenced by vehicular and local sources located to the SE of the study area. The sum of average concentrations of BTEX in rainy and cold dry seasons were of 3.52 ± 0.36 µg m−3 and 4.11 ± 0.38 µg m−3, respectively. Mean concentrations were of 0.74, 1.59, 0.48, and 0.69 µg m−3, for benzene, toluene, ethylbenzene, and p-xylene, respectively. The highest levels of BTEX were found in sites with an urban land-use type of medium-intensity industrial zones with high population density. The lower BTEX concentrations found during the rainy season were probably due to higher solar radiation and temperatures that favored their photochemical degradation. Bi-variate and multivariate analysis showed that the BTEX species were strongly correlated with each other and with temperature and solar radiation, indicating that they originated from common sources. Benzene and toluene correlated strongly with CO and SO2, indicating that they could originate from vehicular exhaust emissions and high-sulfur fuel combustion sources. The health risk assessment showed that the Leon city adult population is at possible risk of developing cancer in their lifetime due to exposure to the measured benzene levels, but indicated no risk of contracting respiratory and cardiovascular diseases due to inhalation of BTEX. The results suggest the need for BTEX emissions reduction policies in the study area, as well as the establishment of a Mexican standard that regulates the maximum permissible limit of these pollutants in ambient air in order to protect the health of the population.

Short-term effects of air pollution on the number of hospital admissions in eight municipalities of the Metropolitan Area of Monterrey, Mexico, were assessed from 2016 to 2019 using a time-series approach. Air quality data were obtained from the Atmospheric Monitoring System of Nuevo Leon State (SIMA) which belongs to SINAICA (National System of Air Quality Information), providing validated data for this study. Epidemiological data were provided by SINAIS (National System of Health Information), considering admission by all causes and specific causes, gender and different age groups. Guadalupe had the highest mean concentrations for SO2, CO and O3, whereas Santa Catarina showed the highest NO2 concentrations. Escobedo and Garcia registered the highest levels for PM10. Only PM10 and O3 exceeded the permissible maximum values established in Mexican official standards. A basal Poisson model was constructed to assess the association between daily morbidity and air pollutants, from this, a second scenario in which daily mean concentrations of air pollutant criteria increase by 10% was considered. Most of pollutants and municipalities studied showed a great number of associations between an increase of 10% in their current concentrations and morbidity, especially for the age group between 5 and 59 years during cold months, excepting ozone which showed a strongest correlation during summer. Results were comparable to those reported by other authors around the world, however, in spite of relative risk index (RRI) values being low, they are of public concern. This study demonstrated that considering the nature of their activities, economically active population and students, they could be more vulnerable to air pollution effects. Results found in this study can be used by decision makers to develop public policies focused on protecting this specific group of the population in metropolitan areas in Mexico.

Short-term effects of air pollution on the health of residents in the Metropolitan Area of Monterrey, Mexico were assessed from 2012–2015 using a time-series approach. Guadalupe had the highest mean concentrations for SO2, CO and O3, whereas Santa Catarina showed the highest NO2 concentrations. Escobedo and Garcia registered the highest levels for PM10. Only PM10 and O3 exceeded the maximum permissible values established in the Mexican official standards. Most of pollutants and municipalities showed a great number of associations between an increase of 10% in their current concentrations and mortality, especially for people &gt, 60 years. Different scenarios resulting from climatic change were built (increases of 5–25% in daily mean temperature), but only the increase of 25% (5 °C) showed a significant association with air pollutant concentrations and mortality. All pollutants and municipalities showed significant increases in relative risk indexes (RRI) resulting from an increase of 5 °C when people &gt, 60 years was considered. Results were comparable to those reported by other authors around the world. The RRI were low but significant, and thus are of public concern. This study demonstrated that the elderly is strongly threatened not only by atmospheric pollution but also by climatic change scenarios in warm and semiarid places.

This work have like purpose quantitative estimates of the short-term effects of air pollution on the health of residents of five municipalities of the Metropolitan Area of Guadalajara, Mexico from 2012 to 2015 using time-series approach. Air Quality was assessed for CO, NO2, SO2, O3 and PM10. Tlaquepaque had the highest mean concentrations for CO (0.88 ppm), NO2 (24.55 ppb), SO2 (0.0036 ppm) and PM10 (53.81 µg m–3), whereas, Zapopan registered the highest mean value for O3 (25.06 ppb). Only PM10 and Ozone exceeded the maximum permissible values established in the Mexican official standards. SO2 presented the highest RRI values in MAG, especially for Zapopan and Tonala, for the majority of the population: 0–59 years and > 60 years. Regarding to CO, excepting Guadalajara and Tlaquepaque, associations were not significant in the most of studied municipalities. The increase of risk as percentage for NO2 was 1.77% for 0–59 years in Guadalajara and Tlaquepaque, 1.87% by respiratory causes in Tlaquepaque, 1.73% > 60 years in Tonala, and 1.25% for 0–59 years in Zapopan. The association between daily mortality and increased O3 levels were significant, however, values were low for all studied municipalities. Finally, regarding to PM10, only Zapopan and Tonala showed statistical significance. This study cannot predict if reductions in criteria pollutants levels would have an important effect on a reduction in daily mortality, however, considering the large size of population exposed, even when observed associations were small but significant, RRI values found are of public concern. Keywords: Relative risk index; Mortality; Megacities; Criteria air pollutants; Mexico.

Emission factors and personal exposure measurements were obtained in the working environment of a brick kiln yard in the municipality of Victoria de Durango, Mexico. Two kinds of kiln were evaluated; one was a fixed traditional kiln (FTK); the other was a local variation of an improved kiln called the ecological Marquez brick kiln (MK2). To distinguish it from the original design, we call it the Marquez kiln Durango (MKD). Ambient emission gases of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and non-methane hydrocarbons (NMHC) were continuously followed using Fourier transform infrared spectrophotometry (FTIR). Elemental carbon (EC) and organic carbon (OC) ambient emissions were sampled on quartz filters and analyzed by chemical coulombimetry. Personal exposure to CO was continuously followed using portable monitors, and personal exposure to inhalable particles with diameters of generally 2.5 μm and smaller (PM2.5) was obtained using Teflon filters in portable particle samplers followed by gravimetric analysis. Results show that the FTK emits more PM2.5, EC, and OC per cooking stage than the MKD. In terms of PM2.5 emission factors, relative to the FTK, the MK2 is 61% smaller and the MKD emission factor is 39% smaller. Against our expectations, the MKD showed higher work environment exposure levels. This is due to the untested changes to the original MK2 design and a mismanagement of the operation processes. Personal exposure to CO and PM2.5 of local brick kiln workers was about three times higher than indoor exposure from the use of three-stone wood cookstoves in Mexico. The analysis of emission plumes from FTK and MKD using a coupled emission model dispersion model allowed us to evaluate the impacts, transport, and deposition area of the particle matter in the area surrounding Durango Brickyard (DB).

Levels of BTEX (benzene, toluene, ethylbenzene, and p-xylene) were determined in ambient air of an urban site located at the center of Mexico (Leon City in Guanajuato State) during two climatic seasons of 2018 (summer and autumn). Ethylbenzene (11.86 &micro, g m&minus, 3) and toluene (11.85 &micro, 3) showed the highest median concentrations during the study period. BTEX concentrations did not show a diurnal pattern but a seasonal trend was observed for benzene and toluene at a significant level of &alpha, = 0.05. Bi-variate and multivariate analysis showed significant positive correlations (at &alpha, = 0.05) among BTEX (excepting benzene), indicating common sources for toluene, ethylbenzene, and p-xylene and a different origin for benzene. A meteorological study was also conducted in order to determine the origin of air masses that could influence the BTEX concentrations in the study site. Finally, it was found that all BTEX species presented hazard quotient values (HQs) &lt, 1, indicating that there is no risk of non-cancer during the studied period. Lifetime cancer risk due to benzene exposure for the adult and child populations studied were estimated to be 7 in 1,000,000 and 1 in 100,000, respectively.

Trace metal concentrations in PM10 were measured in an urban&ndash, industrial site in Le&oacute, n, Mexico in three different seasons. PM10 were collected in quartz fiber filters of 47 mm diameter using low volume equipment operating with a controlled flow of 5 L min&minus, 1 over 24 h. Mass concentrations were gravimetrically determined and it was found that PM10 samples showed values in excess of the Mexican standard and the established values by WHO during cold dry and warm dry seasons. Morphology of selected particles was studied by SEM-EDS analysis, and the elemental composition was determined. Collected samples were analyzed by atomic absorption spectrometry in order to quantify ambient air concentrations of some trace metals (Cu, Co, Zn, Cd, Fe, Mg, and Mn). Median concentrations of trace metals showed the maximum value for iron (3.079 &mu, gm&minus, 3) and the minimum value for Cd (0.050 &mu, 3) over the entire period. From the meteorological analysis, it was found that sources located SW and ESE of the sampling site contributed to the levels of trace metals in PM10 in the studied site. The health risk assessment found that the population of Le&oacute, n is at increased lifetime risk of experiencing cancer because of exposure to these concentrations of PM10 and their trace metal content.

Atmospheric black carbon concentrations were measured at two urban sites (Mexico City and Monterrey), one suburban site (Juriquilla) and one high-altitude site (Altzomoni) in Mexico during 2015 and part of 2016. Black carbon concentrations were compared against other criteria gases finding a strong correlation with carbon monoxide at the urban sites. The carbon monoxide-black carbon correlation for the Mexico City site is 0.77. Urban sites had an average black carbon concentration of above 2.5 μg m−3, the suburban site 0.75 μg m−3, and the high-altitude site 0.27 μg m−3. Compared to other studies, the average levels are comparable, and the urban and suburban locations showed a trend towards increased atmospheric black carbon concentrations at year end. Other urban places (Guadalajara, Cuernavaca, and Iztapalapa) reported black carbon concentrations, but for less than a year. For the first time, a Latin-American country (Mexico) measured black carbon continuously at several sites for a year applying the same data quality assurance.

We measured meteorological parameters and environmental concentrations of hydrogen sulfide (H 2 S) and criteria pollutants at Cerro Prieto, Mexico, from May to July 2010. In addition, non-condensable gases from vent stacks at Cerro Prieto geothermal power plant were sampled and analyzed by gas chromatography–mass spectrometry. A dispersion model, which was validated with environmental measurements, was applied to H 2 S. Criteria pollutants never exceeded the Mexican air quality standards. Results from dispersion modeling were compared against measured concentrations showing acceptable agreements for Chi square goodness of fit ( χ 2 ) in the 95% significance level ( α = 0.05), at afternoons and evening events when boundary layer is decreasing and wind speed is less than 5.5 m s −1 . Determination coefficient of curve fitting for computed concentrations at less than 4 km from the source was 0.513 and farther 0.568. This study was the first to measure criteria pollutants and H 2 S in Cerro Prieto area.

Capture and emission of carbon dioxide of three species ( Buddleia cordata , Senecio praecox and Echeveria gibbiflora ) in the Reserva Ecologica del Pedregal de San Angel (Ecological Reserve of the Pedregal de San Angel), were estimated. CO 2 sampling was carried out in 2010 during the dry (February, March, April and November) and rainy seasons (July to October). On the dry season B. cordata and S. praecox captured 16.14 and 3.25 kg CO 2 , respectively, whereas E. gibbiflora emitted 45.76 kg CO 2 . In the rainy season the exchange of CO 2 was different for the three species. In the dry season, the photosynthetic rate was 22 pmol CO 2 m –2 s –1 for B. cordata, 27 pmolCO 2 m –2 s –1 for S. praecox and 29 pmolCO 2 m –2 s –1 for E. gibbiflora. In the rainy season they were 6, 5.25 and 3 pmol CO 2 m –2 s –1 , respectively. In addition, MODIS data were used to estimate the normalized difference vegetation index (NDVI), indicating that the intensity of greenery at the site increased during the rainy months. This paper explains the contribution of studied plants to the carbon cycle of an ecosystem located within an urban area, and the relationship of environmental variables such as temperature, density photosynthetic photon flux and relative humidity in the capture or emission of CO 2 . This work provides valuable information about the carbon cycle dynamics on urban ecosystems, which can be useful in future studies for climate change mitigation.

espanolLa biomasa zooplanctonica es reconocida como un importante indicador de la produccion secundaria; su variacion espacio-temporal en zonas neriticas es afectada particularmente por las descargas de los rios, por lo que se analiza el efecto espacio temporal de las descargas de aguas continentales en la distribucion de la biomasa zooplanctonica en el sur del Golfo de Mexico, en 5 areas frente a las costas de Veracruz, Tabasco y Campeche. El material analizado proviene de 534 muestras recolectadas en diferentes estaciones climaticas entre 1984 y 2001. Los volumenes de descargas de 5 regiones hidrologicas se obtuvieron de la base de datos gubernamentales. Los resultados muestran que las variaciones de la biomasa durante las estaciones del ano en las diferentes areas son muy similares al patron de las descargas. Los mayores valores de biomasa ocurren enfrente de las costas de Tabasco y los menores frente a Veracruz, donde se tienen las mayores y menores descargas de aguas continentales respectivamente. La variacion de la biomasa depende de las descargas, no solo en terminos de un ciclo anual, sino tambien directamente relacionada con el tamano del volumen vertido al oceano. El analisis de arbol permitio concluir que en el sur del Golfo de Mexico sobre la parte externa de la plataforma y zona oceanica, la biomasa siempre es baja, independiente de la estacion del ano o del area de que se trate. La mayor biomasa ocurre sobre la plataforma en profundidades bajas, pero su magnitud varia dependiendo del area y de la epoca. La biomasa frente a Campeche no depende de las descargas de aguas continentales sino se genera sobre la plataforma de Yucatan. EnglishZooplankton biomass is recognized as an important indicator of secondary production, its spatial and temporal variation in neritic zones is particularly affected by discharges of the rivers, and the spatial-temporal effect of continental water discharges on the distribution of zooplankton biomass in the southern Gulf of Mexico was analyzed for 5 areas off the coasts of Veracruz, Tabasco and Campeche. The analyzed material was obtained from 534 samples collected during different climatic seasons from 1984 to 2001. The discharge volumes of 5 hydrological regions were obtained from the government's data base. The results obtained indicated that biomass variation throughout the seasons in the different areas was very similar to the pattern of discharges. The greater biomass values were recorded off Tabasco and the lower values off Veracruz, where the greater and lower continental water discharges were recorded respectively. Biomass variation depended on the discharges, not only in terms of an annual cycle, but was also directly related to the volumes discharged into the ocean. A Tree analysis made it possible to conclude that biomass is always low on the outer shelf and oceanic region of the southern Gulf of Mexico, independently of the season of the year or of a particular area. A greater biomass was recorded on the shallow shelf, with a magnitude that varied in relation to the area and season. The biomass off Campeche did not depend on the continental water discharges, but was generated on the Yucatan shelf.

"El estudio de los gases de efecto invernadero, como el bióxido de carbono (CO2) y el metano (CH4), tiene una relevancia de carácter global y su acumulación en la atmósfera por actividades humanas afecta el balance radiativo de la Tierra. Las lagunas costeras se consideran reservorios importantes de carbono, pero no es claro si contribuyen como fuentes o sumideros. Este trabajo presenta una estimación de los flujos de CO2 y CH4 en agua-aire en las lagunas de Chautengo y Tres Palos en Guerrero, México, durante la época de secas y también analiza el papel de esos cuerpos de agua en la emisión o captura de carbono, según sus condiciones ambientales. En Chautengo el promedio de captura de CH4 fue 8.7 mg/m2/día y la emisión 15.4 mg/m2/día. La captura de CO2 fue 1001.7 mg/m2/día y la emisión 2241.5 mg/m2/día. En Tres Palos el promedio de captura de CH4 fue 127.7 mg/m2/día y la emisión 1483.3 mg/m2/día. La captura de CO2 presentó un valor promedio de 1475 mg/m2/día y la emisión 95 mg/m2/día. Chautengo presentó un equilibrio entre la captura y emisión de CH4 y CO2, así que podría considerarse un cuerpo de agua neutro en función de los flujos de gas superficial. La laguna de Tres Palos se puede considerar como fuente de CH4 y sumidero de CO2 durante el periodo de estudio. En agua de fondo, la laguna de Chautengo presentó 28 mg/L de carbono inorgánico (CI) promedio y 18 mg/L orgánico (CO). En Tres Palos, las concentraciones en fondo fueron 25 mg/L de CI y 28 mg/L de CO."

"El laboratorio de Zooplancton del Instituto de Ciencias del Mar y Limnología de la UNAM, ha estudiado por más de 25 años el ictioplancton del sur del Golfo de México. Los objetivos han sido determinar qué especies existen, dónde se distribuyen, cuál es su abundancia, qué comunidades forman, cuál es y a qué se debe su variación espacio-temporal. Se ha registrado la presencia de al menos 306 especies, 283 géneros y 120 familias de larvas de peces. La diversidad de especies y la abundancia de larvas aparecen como parámetros opuestos; la mayor densidad de organismos ocurre en áreas costeras y en plataforma media y disminuye hacia la zona oceánica; la diversidad en cambio es mayor en áreas oceánicas, al borde de la plataforma continental y se reduce hacia estaciones costeras. En general, la distribución de la abundancia de las larvas tiene un patrón recurrente y está determinada por las áreas y épocas de desove de las especies, por la disponibilidad de alimento y los procesos físicos, principalmente corrientes, descargas de agua continental y mezcla. La distribución de las larvas en la columna de agua parece depender del hábitat de sus adultos, aquellas cuyos adultos viven la zona costera se encuentran primordialmente en los primeros 30 m; las de origen oceánico ocupan generalmente capas con profundidades mayores a 50 m. Todas tienden a una mayor dispersión en la columna durante la noche. Se ha determinado la presencia recurrente de cuatro comunidades: a) Costera, b) Nerítica Interna, c) Nerítica Externa y d) Oceánica."

Se analizó estacionalmente la biomasa zooplanctónica (BZ) y la densidad ictioplanctónica (DI) en la columna de agua sobre la plataforma continental del sur del Golfo de México, para determinar sus patrones de distribución vertical y establecer si existe una relación entre ambos componentes. Se muestrearon cinco niveles de profundidad: 0-6 m, 6-12 m, 12-18 m, 45-55 m y 95-105 m. El patrón de distribución vertical de la BZ y de la DI fue similar en todas las épocas de muestreo, con la mayor concentración de organismos en los niveles superficiales y la más baja en los niveles más profundos. Estos resultados sugieren que la columna de agua en el área de estudio puede estar dividida en una capa superficial (0 a 18 m) y una capa profunda (45 a 100 m) y que las diferencias estacionales pueden ser atribuidas a los procesos de mezcla. Esta diferencia entre las capas superficiales y las profundas ocurre porque, en general, las capas superficiales de la columna de agua son las más productivas. La relación entre la BZ y la DI fue positiva y significativa (ANCOVA, P

Se analiza la influencia de El Niño Oscilación del Sur (ENSO) sobre la variación de la abundancia de las larvas del pez Bregmaceros cantori en el sur del Golfo de México. El estudio se desarrolló entre 1987 y 1996, usando 20 cruceros oceanográficos. La abundancia de B. cantori fue relacionada con: (1) la anomalía de la temperatura superficial del mar (SSTA) del Océano Pacífico central ecuatorial, (2) la temperatura promedio de la capa superficial de 30 m, de datos de las campañas, (3) las descargas de aguas continentales con datos provenientes de la estación hidrológica mas cercana al área de estudio. Hubo una alta variabilidad de la abundancia de larvas de B. cantori a través del tiempo, pero no se registró un patrón estacional. Durante el periodo de estudio ocurrieron tres eventos de El Niño: 1987, 1992 y 1995. Los análisis estadísticos indicaron diferencias significativas en la abundancia de larvas entre los años de El Niño y años normales, sin el evento de El Niño. Se encontraron altas abundancias de B. cantori en los periodos de El Niño en comparación con los años normales. Es posible que las mayores abundancias de larvas de B. cantori durante años de El Niño estén asociadas con relaciones depredador-presa.

Environmental context Dimethylsulfide (DMS), the main biogenic sulfur compound in the atmosphere, is produced by the marine biosphere and plays an important role in the atmospheric sulfur cycle. This study recorded the spatial variability of DMS and dissolved and particulate dimethylsulfoniopropionate (DMSP) in the water column of the southern Gulf of Mexico. The results suggest that the spatial variability of DMS and DMSP is directly related to the hydrodynamics of the study area. Abstract The spatial variability of dimethylsulfide (DMS) and dissolved and particulate dimethylsulfoniopropionate (DMSPd and DMSPp) was recorded in the southern Gulf of Mexico at three different depths (10, 30 and 60m) in January 2013. DMS and DMSP values were recorded through solid-phase microextraction coupled to gas chromatography. Average concentrations of DMS (2.8±1.5nM), DMSPd (1.7±0.9nM) and DMSPp (352±157nM) were significantly correlated with chlorophyll-a concentrations and the depth of the mixed layer. Vertical concentration profiles were similar, indicating a well-mixed water column with a thermocline at a depth of 50–100m. Average DMS sea-to-air flux was 5.0±1.7µmolm–2day–1. The greatest fluxes were recorded at the stations in the western region of the study area, owing to the combined effect of high DMS concentrations (3.7–7.21nM) and a high wind speed (4.4–6.8ms–1). The greatest concentrations were recorded at the stations nearest the coast. The distribution of DMS and DMSP was apparently related to the oceanic hydrodynamics.

Coagulation and fibrinolysis tests were performed in 14 patients with hydatidiform mole before any significant therapy was given and again, after evacuation of the mole, in eight instances. The results were compared with those found in a group of ten volunteers with normal pregnancies. The most frequent abnormalities in the problem cases were a shortening of the partial thromboplastin time and a prolongation of the thrombin time. From a total of seven cases with complete hematologic profiles before and shortly after evacuation of the mole, five showed important drops in platelets and fibrinogen. The most altered profiles occurred after expulsion of the mole in cases with important previous uterine activity. The findings suggested a latent state of hypercoagulability with higher turn over rate of fibrinogen and increased levels of fibrinogen-fibrin degradation products, that may exist even before the mechanism of expulsion begins. It was concluded that the alterations in coagulation and fibrinolysis seen in molar pregnancies most likely have a multifactorial pathogenesis, but the initiating causes must depend on several events taking place in the trophoblast itself and their consequences upon a very distorted intervillous blood circulation.

The potential differences in hematologic profiles of blood samples drawn simultaneously from the right utero-ovarian vein and from the upper extremity were investigated in four patients with uncomplicated molar pregnancy in stable obstetric conditions. The patients had undergone no previous chemotherapy and were scheduled for total abdominal hysterectomies. The dominant abnormalities in uterine venous blood were prolongation of thrombin time; shortening of activated partial thromboplastin time; positive protamine sulfate test; and increase in coagulation factors II and VII, with a tendency to low values in factor V. Peripheral samples gave almost parallel results in all altered and normal tests, except in one case with very striking differences in factors II, V, VII and X. Several local and systemic influences are discussed. It is concluded that molar pregnancy seems to have important systemic mechanisms affecting the stability of the blood coagulation homeostasis, which act in addition to those at a local level.

"Changes in the composition and abundance of fish larvae in the water column were analyzed throughout an annual cycle (1994-1995) in the southern Gulf of Mexico, in order to establish the difference between the habitat of the larvae and the effect of oceanographic events on larval vertical distribution. The study area comprised the continental shelf off Tabasco and Campeche in the southern Gulf of Mexico. Samples were collected at five water column levels: 0-6, 6-12, 12-18, 45-55 and 95-105 m. A total of 118 taxa were identified, 52 were dominant species, 33 were larvae of neritic parents and 19 were larvae of mesopelagic parents. The results indicate that the water column presented two layers above the 105 m depth: a surface layer (0-18 m) and a deep layer (45-105 m). The greatest density of larval species that inhabit neritic areas as adults was recorded in the surface layer (0-18 m), while larvae of which the parents inhabit mesopelagic areas were found in the deep layer (45-105 m). The mixing of the water column was the most important physical factor regarding the variation in the vertical distribution of the larvae of both groups, particularly in winter. However, the biology of each species and the habit to occupy a particular depth was the most important factor that determined their distribution in the water column."