Carlos Pereira
Universidad Central de Venezuela, Postgrado de Ecología, Graduate Student
- Doctor of Science, Ecology mention; MSc. Sanitary Engineering, water quality mention; BSc. Marine Biologistedit
Microphytobenthos is a community that groups benthic photosynthetic microorganisms. In Venezuela and the other countries in the Caribbean Sea, this group has been scarcely studied, so its diversity is unknown. This study aims to describe... more
Microphytobenthos is a community that groups benthic photosynthetic microorganisms. In Venezuela and the other countries in the Caribbean Sea, this group has been scarcely studied, so its diversity is unknown. This study aims to describe the spatial and temporal variations of its composition and abundance in the central coastal zone of Venezuela. Samplings were conducted monthly from June 2014 to March 2015, in random stations at depths less than 20 m. Richness and abundance data were processed through multivariate hypothesis tests (Anosim – SIMPER – nMDS). A total of 327 species were identified, with a dominance of diatoms and dinoflagellates, without significant spatial and temporal variations. In terms of abundance, the most representative group was diatoms (68 %), followed by cyanobacteria (28 %). The microfitobenthos presented a temporal variability in which the highest densities were reached between July and August, while the rest of the months presented similar abundances. Thus, standard abundances were obtained in all the samples according to that found in other areas of the world, with notable differences between the microphytobenthos of the evaluated substrates, and a high and constant specific richness throughout the year.
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El fitoplancton es un indicador excelente de la calidad del agua y de la condición del ambiente. Con la finalidad de identificar las especies de microalgas indicadoras de las condiciones hidrográficas de la zona marina y costera de una... more
El fitoplancton es un indicador excelente de la calidad del agua y de la condición del ambiente. Con la finalidad de identificar las especies de microalgas indicadoras de las condiciones hidrográficas de la zona marina y costera de una playa ubicada en la zona central de Venezuela y la variabilidad espacial y temporal de su estructura comunitaria, se realizaron 13 muestreos mensuales durante el período entre abril de 2010 – abril de 2011. Se recolectaron muestras de fitoplancton y se estimaron variables fisicoquímicas de interés para la calidad del agua. La comunidad fitoplanctónica estuvo representada por 168 especies o morfotipos distribuidos en 94 diatomeas, 55 dinoflagelados, ocho clorofitas, cinco euglenofitas y un flagelado, y se evidenciaron cambios temporales en su estructura comunitaria, relacionados con el aporte de aguas continentales durante las épocas de máximas precipitaciones y un ascenso de aguas profundas durante los primeros meses del año. Se evidencia una diversid...
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Phytoplankton is an excellent indicator of water quality and the environmental conditions. In order to identify the microalgae species that are indicators of the hydrographic conditions of the marine and coastal area of a beach located... more
Phytoplankton is an excellent indicator of water quality and the environmental conditions. In order to identify the microalgae species that are indicators of the hydrographic conditions of the marine and coastal area of a beach located in the central zone of Venezuela and to understand the spatial and temporal variability of its community structure, 13 monthly samplings were conducted from April 2010 to April 2011. Phytoplankton samples were collected and physicochemical variables of water quality were estimated. The phytoplankton community showed a richness of 168 species or morphotypes distributed in 94 diatoms, 55 dinoflagellates, 8 chlorophytes, 5 euglenophytes, and one flagellate. Temporary changes were evidenced in its community structure, related to the contribution of continental waters during periods of maximum rainfall and a deep water ascent during the first months of the year. There was a high biological diversity of this community with a variety of species that included benthic, planktonic, coastal, estuarine, and oceanic microalgae. Additionally, the species Trichodesmium thiebautii, Pseudonitzschia serieta, Asterionellopsis glacialis, Chaetoceros socialis, Thalassiosira nordeskioldii, and Tripos massiliensiswere identified as bioindicators of the environmental conditions of the area, due to their relationship with specific physicochemical variables and their ability to differentiate the community spatially and temporally.
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Meiobenthos is a sediment-dwelling community with various taxonomic groups ranging in size from 63 to 500 μm. As a matter and energy link between primary producers and macrofauna, they have other functions in the ecosystem. Since this... more
Meiobenthos is a sediment-dwelling community with various taxonomic groups ranging in size from 63 to 500 μm. As a matter and energy link between primary producers and macrofauna, they have other functions in the ecosystem. Since this group has been scarcely studied in Venezuela, it was proposed to analyze the spatial and temporal variations in the composition and abundance of subtidal meiobenthos in the country’s central coast. Samplings were conducted monthly from June 2014 to March 2015. In each sampling campaign, 12 random stations were established, and three samples were taken at each using a cylindrical sampler of 5.0 cm internal diameter. Organisms were identified and counted using microscopes, and data was processed using hypothesis tests (ANOSIM) and multivariate analyzes (SIMPER, nMDS). Meiobenthos showed a richness of 164 morphotypes and 14 phyla, with a dominance of planktonic copepods and foraminifers, followed by cnidarians and mollusks. Out of the total species report...
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Punta de Piedras Lagoon is a coastal lagoon located south of Margarita Island, in the Venezuelan Caribbean Sea. This lagoon has ecological and economic importance for the inhabitants of nearby communities. Currently, the urban and... more
Punta de Piedras Lagoon is a coastal lagoon located south of Margarita Island, in the Venezuelan Caribbean Sea. This lagoon has ecological and economic importance for the inhabitants of nearby communities. Currently, the urban and industrial development in its surroundings represents a potential source of pollutants, providing concentrations of nutrients that could affect the ecological balance of the area. The trophic status of Punta de Piedras Lagoon was evaluated using various trophic indices. The concentrations of chlorophyll-a and nutrients (ammonium, nitrites, nitrates, and orthophosphates) were estimated in 10 stations with a monthly frequency from February 2005 to January 2006.
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Se presenta una contribución al conocimiento de la biología del cangrejo violinista Minuca rapax, mediante un estudio morfométrico y de parámetros de crecimiento poblacional en el caño Francés del río San Juan, estado Monagas. El análisis... more
Se presenta una contribución al conocimiento de la biología del cangrejo violinista Minuca rapax, mediante un estudio morfométrico y de parámetros de crecimiento poblacional en el caño Francés del río San Juan, estado Monagas. El análisis morfométrico se realizó con muestras obtenidas en cuatro campañas entre 2012 y 2013. Se analizó la proporción sexual y las relaciones talla-peso, y se estimaron los parámetros de crecimiento poblacional mediante el uso del programa FiSAT II. Se obtuvo un aumento progresivo de la abundancia de M. rapax durante las cuatro campañas. Espacialmente, se observó mayor abundancia en las estaciones más alejadas del caño principal. Se evidencia una población dominada por los machos, un aumento progresivo en el reclutamiento y una similitud en la estructura de tallas en ambos sexos. M. rapax presentó un crecimiento isométrico en el caso de los machos y alométrico en el caso de las hembras (usando la ecuación de Ricker). En cuanto a los parámetros de crecimiento, se obtuvo una longitud asintótica (L∞ = 20,62 mm para las hembras y L∞ = 21,89 para los machos) similar a la estimada en otros estudios con otras poblaciones de M. rapax; pero una tasa de crecimiento y edad límite mayor. La población presentó curvas de crecimiento en longitud y peso diferentes para ambos sexos.
A contribution to the knowledge of the biology of the mudflat fiddler Minuca rapax is presented through a study about morphometry and population growth in Caño Francés, San Juan river, Monagas state. The morphometric analysis was carried out with samples obtained in four campaigns in 2012 and 2013. The sexual proportion and length-weight relationships were analyzed and population growth parameters were estimated using the program FiSAT II. A progressive increase in the abundance of M. rapax was obtained during the four seasons. Spatially, greater abundance was observed in the stations further away from the main stream. There is evidence of a population dominated by males, a progressive increase in recruitment, and similarity in the size structure in both sexes. M. rapax showed allometric growth in females and isometric growth in males (using the Ricker equation). Regarding growth parameters, an asymptotic length was obtained (L∞ = 20.62 mm for females and L∞ = 21.89 for males), similar to that estimated in other studies with other populations of M. rapax; but with a higher growth rate and age limit. The population presented different growth curves in length and weight for both sexes.
A contribution to the knowledge of the biology of the mudflat fiddler Minuca rapax is presented through a study about morphometry and population growth in Caño Francés, San Juan river, Monagas state. The morphometric analysis was carried out with samples obtained in four campaigns in 2012 and 2013. The sexual proportion and length-weight relationships were analyzed and population growth parameters were estimated using the program FiSAT II. A progressive increase in the abundance of M. rapax was obtained during the four seasons. Spatially, greater abundance was observed in the stations further away from the main stream. There is evidence of a population dominated by males, a progressive increase in recruitment, and similarity in the size structure in both sexes. M. rapax showed allometric growth in females and isometric growth in males (using the Ricker equation). Regarding growth parameters, an asymptotic length was obtained (L∞ = 20.62 mm for females and L∞ = 21.89 for males), similar to that estimated in other studies with other populations of M. rapax; but with a higher growth rate and age limit. The population presented different growth curves in length and weight for both sexes.
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Macroalgae of the marine subtidal area of the Miranda state, Venezuela Marine macroalgae have an important role in the ecology of aquatic ecosystems because they contribute to primary productivity and provide food and habitat for many... more
Macroalgae of the marine subtidal area of the Miranda state, Venezuela Marine macroalgae have an important role in the ecology of aquatic ecosystems because they contribute to primary productivity and provide food and habitat for many species. The study of these communities in the Miranda state has been scarce and they have mainly focused on the intertidal zone, so an inventory of macroalgae in the subtidal zone between Chirimena and Puerto Francés was considered. To do this, samplings were done monthly from June 2014 to March 2015 at twelve randomly selected stations between 5 and 25 m deep. Macroalgae were identified in the laboratory using microscopes and specialized literature. A total of 119 species of macroalgae were identified, dominated by the Rhodophyta phylum, followed by Ochrophyta phylum. Two increases in species richness were observed during the study time: the first of them was associated with the intensity of the trade winds during the first months of the year which promote upwelling in the Venezuelan coast. This was evidenced by the presence of some indicator species of this phenomenon. The second increase occurred at the beginning of the rainy season followed by a decrease during the months with maximum rainfall. With this inventory, a total of 45 unreported species for the Miranda state, and Gayliella taylorii, Gayliella fimbriata and Rhodymenia divaricata species for the Venezuelan coast were registered.
RESUMEN: Las macroalgas marinas tienen un papel importante en la ecología de los ecosistemas acuáticos, ya que además de contribuir con la productividad primaria, proporcionan alimento y hábitat a muchas especies. Los estudios de estas comunidades en el estado Miranda han sido escasos y enfocados fundamentalmente en la zona intermareal, por lo que se planteó realizar un inventario de las macroalgas de la zona submareal entre Chirimena y Puerto Francés. Para ello, se realizaron muestreos mensuales desde junio de 2014 hasta marzo de 2015 en doce estaciones seleccionadas aleatoriamente entre 5 y 25 m de profundidad. La identificación de las macroalgas se realizó en el laboratorio con el uso de microscopios y claves especializadas. Se identificaron 119 especies de macroalgas dominadas por el phylum Rhodophyta, seguido por el phylum Ochrophyta. Se observaron dos aumentos del número de especies durante el periodo de estudio. El primero asociado a la intensidad de los vientos alisios durante los primeros meses del año, los cuales promueven la surgencia costera, y que se evidenció con la presencia de especies indicadoras de este fenómeno. El segundo aumento del número de especies ocurrió al principio de la época de lluvias, con una disminución posterior durante los meses con máximas precipitaciones. Con este inventario, se contribuyó con 45 especies no reportadas para el estado Miranda y las especies Gayliella taylorii, Gayliella fimbriata y Rhodymenia divaricata para la costa venezolana.
RESUMEN: Las macroalgas marinas tienen un papel importante en la ecología de los ecosistemas acuáticos, ya que además de contribuir con la productividad primaria, proporcionan alimento y hábitat a muchas especies. Los estudios de estas comunidades en el estado Miranda han sido escasos y enfocados fundamentalmente en la zona intermareal, por lo que se planteó realizar un inventario de las macroalgas de la zona submareal entre Chirimena y Puerto Francés. Para ello, se realizaron muestreos mensuales desde junio de 2014 hasta marzo de 2015 en doce estaciones seleccionadas aleatoriamente entre 5 y 25 m de profundidad. La identificación de las macroalgas se realizó en el laboratorio con el uso de microscopios y claves especializadas. Se identificaron 119 especies de macroalgas dominadas por el phylum Rhodophyta, seguido por el phylum Ochrophyta. Se observaron dos aumentos del número de especies durante el periodo de estudio. El primero asociado a la intensidad de los vientos alisios durante los primeros meses del año, los cuales promueven la surgencia costera, y que se evidenció con la presencia de especies indicadoras de este fenómeno. El segundo aumento del número de especies ocurrió al principio de la época de lluvias, con una disminución posterior durante los meses con máximas precipitaciones. Con este inventario, se contribuyó con 45 especies no reportadas para el estado Miranda y las especies Gayliella taylorii, Gayliella fimbriata y Rhodymenia divaricata para la costa venezolana.
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En los ecosistemas rocosos costeros, los anfípodos cumplen un papel importante al representar un vínculo entre los productores primarios y organismos de niveles tróficos superiores. No obstante, son pocos los estudios que han abordado la... more
En los ecosistemas rocosos costeros, los anfípodos cumplen un papel importante al representar un vínculo entre los productores primarios y organismos de niveles tróficos superiores. No obstante, son pocos los estudios que han abordado la estructura comunitaria y dinámica de este grupo. Considerando estos aspectos, en esta investigación se planteó como objetivo determinar las variaciones espaciales y temporales de la estructura comunitaria de los anfípodos en dos localidades costeras de Venezuela, y su relación con las variables abióticas salinidad, precipitación, temperatura, pH, oxígeno disuelto, amonio, nitritos, nitratos y fosfatos. Se realizaron muestreos mensuales de los organismos para estimar la abundancia y riqueza de la comunidad de anfípodos en las playas Caracolito y Caimán, desde junio de 2014 hasta junio de 2015. Se registró un total de 20 especies, representantes de 10 familias de anfípodos. Las especies más abundantes fueron Hyale pygmaea, Elasmopus pectinicrus y Amphitoe marcuzzii. No se encontraron diferencias estadísticamente significativas en la riqueza de especies entre meses o playas. Se observó una variabilidad temporal de la abundancia total de individuos en ambas localidades, con la mayor densidad en agosto (618 ± 3 ind/100 cm 2) y la menor en diciembre (48 ± 2 ind/100 cm 2). Los patrones de abundancia se relacionan con las variables fisicoquímicas temperatura y salinidad, lo que sugiere que la comunidad de anfípodos puede ser sensible a las fluctuaciones de las condiciones ambientales. Palabras clave: Caribe sur, crustáceos, peracáridos, plataforma rocosa, variabilidad temporal.
Amphipod community dynamics in two rocky shores of Miranda state, Venezuela In rocky shores ecosystems, amphipods play an important role by representing a link between primary producers and organisms at higher trophic levels. However, there are very few studies on the community structure and dynamics of this group. Considering these aspects, the objective of this research was to know the spatial and temporal variations of the community structure of amphipods in two coastal localities of Venezuela and their relationship with the abiotic variables salinity, precipitation, temperature, pH, dissolved oxygen, ammonium, nitrite, nitrate, and phosphate. Monthly samples of the abundance and richness of the amphipod community were carried out on the Caracolito and Caimán beaches between June 2014 and June 2015. A total of 20 species were recorded, representing 10 families of amphipods. The most abundant species were Hyale pygmaea, Elasmopus pectinicrus, and Amphitoe marcuzzii. No significant differences were found in species richness between months or beaches. A temporal variability of the total abundance of individuals was observed in both locations, with the highest density in August (618 ± 3 ind / 100 cm2) and the lowest in December (48 ± 2 ind / 100 cm2). Also, a relationship was found between the abundance patterns and the physicochemical variables temperature and salinity, which suggests that the amphipod community is sensitive to fluctuations in environmental conditions.
Amphipod community dynamics in two rocky shores of Miranda state, Venezuela In rocky shores ecosystems, amphipods play an important role by representing a link between primary producers and organisms at higher trophic levels. However, there are very few studies on the community structure and dynamics of this group. Considering these aspects, the objective of this research was to know the spatial and temporal variations of the community structure of amphipods in two coastal localities of Venezuela and their relationship with the abiotic variables salinity, precipitation, temperature, pH, dissolved oxygen, ammonium, nitrite, nitrate, and phosphate. Monthly samples of the abundance and richness of the amphipod community were carried out on the Caracolito and Caimán beaches between June 2014 and June 2015. A total of 20 species were recorded, representing 10 families of amphipods. The most abundant species were Hyale pygmaea, Elasmopus pectinicrus, and Amphitoe marcuzzii. No significant differences were found in species richness between months or beaches. A temporal variability of the total abundance of individuals was observed in both locations, with the highest density in August (618 ± 3 ind / 100 cm2) and the lowest in December (48 ± 2 ind / 100 cm2). Also, a relationship was found between the abundance patterns and the physicochemical variables temperature and salinity, which suggests that the amphipod community is sensitive to fluctuations in environmental conditions.
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Meiobenthos is a sediment-dwelling community with various taxonomic groups ranging in size from 63 to 500 µm. As a matter and energy link between primary producers and macrofauna, they have other functions in the ecosystem. Since this... more
Meiobenthos is a sediment-dwelling community with various taxonomic groups ranging in size from 63 to 500 µm. As a matter and energy link between primary producers and macrofauna, they have other functions in the ecosystem. Since this group has been scarcely studied in Venezuela, it was proposed to analyze the spatial and temporal variations in the composition and abundance of subtidal meiobenthos in the country's central coast. Samplings were conducted monthly from June 2014 to March 2015. In each sampling campaign, 12 random stations were established, and three samples were taken at each using a cylindrical sampler of 5.0 cm internal diameter. Organisms were identified and counted using microscopes, and data was processed using hypothesis tests (ANOSIM) and multivariate analyzes (SIMPER, nMDS). Meiobenthos showed a richness of 164 morphotypes and 14 phyla, with a dominance of planktonic copepods and foraminifers, followed by cnidarians and mollusks. Out of the total species reported, 84 are strictly benthic. Regarding abundance, there was a greater representation of foraminifera, followed by nematodes and mollusks, with values higher than those reported for tropical areas. Spatially, no differences were found in the composition and abundance of this community. However, two maximums were found throughout the study period, one starting in June until reaching maximum densities between August and October and the second one in February.
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Zooplankton is a community that occupies a key position in pelagic food webs as a link between primary producers and the highest trophic levels. It has been scarcely studied in the central area of Venezuela. In this survey, we analyze... more
Zooplankton is a community that occupies a key position in pelagic food webs as a link between primary producers and the highest trophic levels. It has been scarcely studied in the central area of Venezuela. In this survey, we analyze spatial and temporal variations of composition and density of zooplankton, and its relationship with the environmental conditions of the coastal zone between Chirimena and Puerto Francés, Miranda state, Venezuela. Sampling was carried out monthly from June 2014 to March 2015, by performing horizontal trawls with a standard zooplankton net. To analyze the results, hypothesis tests and multivariate analyses were applied. The surveyed area showed two seasons: rainy and drought, which by themselves do not explain the temporal variation of the estimated variables. This zooplankton community had a richness of 121 species with representatives of 12 phyla, a typical feature of the coastal zooplankton community in the Caribbean Sea. The most representative organisms in terms of richness were copepods, cnidarians, and decapods. Zooplankton abundance had maximum values between June and September with an average of 98 ± 25 ind/m 3 and the lowest between February and March with an average of 23 ± 13 ind/m 3 , which are characteristic densities of oligotrophic waters.
Resumen: El zooplancton ocupa una posición clave en las tramas tróficas pelágicas como nexo entre los productores primarios y los niveles tróficos más altos. Esta comunidad ha sido escasamente estudiada en la zona central de Venezuela, por lo que se planteó analizar las variaciones espaciales y temporales de la composición y densidad del zooplancton, así como su relación con las condiciones ambientales de la zona costera ubicada entre Chirimena y Puerto Francés, estado Miranda. Los muestreos fueron realizados mensualmente desde junio de 2014 hasta marzo de 2015, mediante arrastres horizontales en la superficie. Para el análisis de los resultados, se hicieron pruebas de hipótesis y se aplicaron análisis multivariados. La zona evaluada presentó condiciones ambientales en las que dominan dos épocas: lluvia y sequía, que por sí solas no explican la variación temporal de las variables biológicas estimadas. El zooplancton estuvo representado por 117 especies de 12 phyla, típica de ambientes costeros del mar Caribe. Los organismos más representativos en términos de riqueza fueron los copépodos, cnidarios y decápodos. La densidad presentó sus máximos entre junio y septiembre con una media de 98 ± 25 ind/m 3 y sus mínimos entre febrero y marzo con una media de 23 ± 13 ind/m 3 , las cuales son densidades características de aguas oligotróficas. Palabras claves: Distribución, abundancia, ecología marina, Venezuela, zooplancton.
Resumen: El zooplancton ocupa una posición clave en las tramas tróficas pelágicas como nexo entre los productores primarios y los niveles tróficos más altos. Esta comunidad ha sido escasamente estudiada en la zona central de Venezuela, por lo que se planteó analizar las variaciones espaciales y temporales de la composición y densidad del zooplancton, así como su relación con las condiciones ambientales de la zona costera ubicada entre Chirimena y Puerto Francés, estado Miranda. Los muestreos fueron realizados mensualmente desde junio de 2014 hasta marzo de 2015, mediante arrastres horizontales en la superficie. Para el análisis de los resultados, se hicieron pruebas de hipótesis y se aplicaron análisis multivariados. La zona evaluada presentó condiciones ambientales en las que dominan dos épocas: lluvia y sequía, que por sí solas no explican la variación temporal de las variables biológicas estimadas. El zooplancton estuvo representado por 117 especies de 12 phyla, típica de ambientes costeros del mar Caribe. Los organismos más representativos en términos de riqueza fueron los copépodos, cnidarios y decápodos. La densidad presentó sus máximos entre junio y septiembre con una media de 98 ± 25 ind/m 3 y sus mínimos entre febrero y marzo con una media de 23 ± 13 ind/m 3 , las cuales son densidades características de aguas oligotróficas. Palabras claves: Distribución, abundancia, ecología marina, Venezuela, zooplancton.
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ABSTRACT: Phytoplankton is a biotic community that together with phytobenthos, constitutes the base of aquatic trophic webs, being responsible for most of the primary oceanic production. Knowledge about its composition makes it possible... more
ABSTRACT: Phytoplankton is a biotic community that together with phytobenthos, constitutes the base of aquatic trophic webs, being responsible for most of the primary oceanic production. Knowledge about its composition makes it possible to complement water quality evaluations as microalgae are excellent indicators of environmental conditions. In this study, it was proposed to analyze the community structure of microphytoplankton and its association with physical and chemical variables of the coastal zone between Cabo Codera and Paparo, including two important rivers, in Brión municipality of Miranda state. Phytoplankton samples were taken with trawls and bottles at six stations from April 2010 to April 2011 to estimate the composition and abundance of microalgae. Physical and chemical variables of the water were estimated. A total of 140 species were identified, distributed in diatoms (66%), dinoflagellates (27%), chlorophytes (2%), cyanobacteria (2%), euglenophytes (2%), and flagellates (1%). A distribution of organisms defined by the continent-ocean pattern was observed, in which the fluvial stations were mostly represented by diatoms, while a high percentage of dinoflagellates was observed in the marine stations in some months. The richness and biodiversity index were higher in the marine stations than in the fluvial ones. It was observed that the coastal upwelling influences the distribution of the marine microphytoplankton during the first months of the year, while in the high rainfall season, the contribution of the rivers influences its composition.
RESUMEN: El fitoplancton es una comunidad biótica que junto al fitobentos constituyen la base de las tramas tróficas acuáticas, siendo responsables de la mayor parte de la producción primaria oceánica. Conocer su composición permite complementar las evaluaciones de calidad del agua, ya que son indicadores excelentes de las condiciones ambientales. En este trabajo, se planteó analizar la estructura comunitaria del microfitoplancton y su asociación con variables físicas y químicas de la zona marina y costera entre Cabo Codera y Paparo, incluyendo dos ríos importantes, en el municipio Brión del estado Miranda. Muestras de fitoplancton fueron obtenidas con redes de arrastre y botellas en seis estaciones durante el período abril 2010-abril 2011 para la estimación de la composición y abundancia de las microalgas. Variables físicas y químicas del agua fueron estimadas. Un total de 140 especies fueron identificadas, distribuidas en diatomeas (66 %), dinoflagelados (27 %), clorofitas (2 %), cianobacterias (2 %), euglenofitas (2 %) y flagelados (1 %). Se observó una distribución de los organismos definida por el patrón continente-océano, en la que las estaciones fluviales estuvieron representadas en su mayoría por diatomeas, mientras que en las estaciones marinas, se observó un porcentaje alto de dinoflagelados en algunos meses del año. La riqueza y el índice de biodiversidad fueron más altos en las estaciones marinas que en las fluviales. Se pudo apreciar que la surgencia costera incide sobre la distribución del microfitoplancton marino durante los primeros meses del año, mientras que en la época de altas precipitaciones, el aporte de los ríos influye sobre su composición. Palabras claves: comunidad, ecología marina, fitoplancton, mar Caribe, microalgas marinas.
RESUMEN: El fitoplancton es una comunidad biótica que junto al fitobentos constituyen la base de las tramas tróficas acuáticas, siendo responsables de la mayor parte de la producción primaria oceánica. Conocer su composición permite complementar las evaluaciones de calidad del agua, ya que son indicadores excelentes de las condiciones ambientales. En este trabajo, se planteó analizar la estructura comunitaria del microfitoplancton y su asociación con variables físicas y químicas de la zona marina y costera entre Cabo Codera y Paparo, incluyendo dos ríos importantes, en el municipio Brión del estado Miranda. Muestras de fitoplancton fueron obtenidas con redes de arrastre y botellas en seis estaciones durante el período abril 2010-abril 2011 para la estimación de la composición y abundancia de las microalgas. Variables físicas y químicas del agua fueron estimadas. Un total de 140 especies fueron identificadas, distribuidas en diatomeas (66 %), dinoflagelados (27 %), clorofitas (2 %), cianobacterias (2 %), euglenofitas (2 %) y flagelados (1 %). Se observó una distribución de los organismos definida por el patrón continente-océano, en la que las estaciones fluviales estuvieron representadas en su mayoría por diatomeas, mientras que en las estaciones marinas, se observó un porcentaje alto de dinoflagelados en algunos meses del año. La riqueza y el índice de biodiversidad fueron más altos en las estaciones marinas que en las fluviales. Se pudo apreciar que la surgencia costera incide sobre la distribución del microfitoplancton marino durante los primeros meses del año, mientras que en la época de altas precipitaciones, el aporte de los ríos influye sobre su composición. Palabras claves: comunidad, ecología marina, fitoplancton, mar Caribe, microalgas marinas.
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Punta de Piedras Lagoon is a coastal environment, close to an important urban development on Margarita Island, which influences on the physicochemical characteristics of its waters. With the purpose of knowing its hydrographic conditions,... more
Punta de Piedras Lagoon is a coastal environment, close to an important urban development on Margarita Island, which influences on the physicochemical characteristics of its waters. With the purpose of knowing its hydrographic conditions, a study was carried out over a year with monthly samplings, in which 10 stations were established to measure the variables: temperature, salinity, suspended organic and inorganic matter, dissolved oxygen, chlorophyll-a, pheopigments, ammonia, nitrites, nitrates, and phosphates. Temporarily, it was observed that the variability of hydrographic conditions was associated with atmospheric conditions. Spatially, homogeneity of the distribution of temperature and salinity was noticed, while the other variables, with the exception of dissolved oxygen, presented higher concentrations in a channel located in the south of the lagoon, which presents little exchange of water with the rest of the lagoon and sewage inputs. Additionally, positive relationships between nitrogenous nutrients and rainfall were obtained, which were negatively associated with wind, salinity, and phosphates. Negative relationship between dissolved oxygen and organic matter suggests oxidative processes while a negative relationship between chlorophyll-a and dissolved oxygen indicates consumption by phytoplankton. These results demonstrate the influence of rainfall and coastal upwelling on the hydrography of this body of water.
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In communities on the central coast of Venezuela, massive poisonings occur that cause fish mortality and effects on the health of people and domestic animals. To understand the dynamics of these phenomena, it is necessary to know the... more
In communities on the central coast of Venezuela, massive poisonings occur that cause fish mortality and effects on the health of people and domestic animals. To understand the dynamics of these phenomena, it is necessary to know the community structure of phytoplankton during events. With the support of the community, samples of phytoplankton were collected during three massive poisonings that occurred in 2010, 2014, and 2015. And also, physicochemical variables of the water were determined. As a result, a diverse community was obtained with the presence of diatoms, dinoflagellates, cyanobacteria, and euglenophytes with significant differences in the composition in each event. However, in the three massive poisonings, an overgrowth of dinoflagellates of the genus Ostreopsis coincides, accompanied by the euglenophyte Eutreptiella gymnastica, which are widely known for their toxic effects on algal blooms when they reach densities greater than 1,000 cell/liter. When comparing these conditions with those in which there is no intoxication, it can be seen that the proportion of the density of Ostreopsis spp with respect to the rest of the dinoflagellates exceeds 50%, which could serve as an indicator during harmful algal blooms of these species.
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Modified tannins are used as deflocculant additives in the formulation of water-based drilling fluids (WBDF) for drilling operations in any scenario. Due to their high heavy metals content, these additives are toxic and hazardous for any... more
Modified tannins are used as deflocculant additives in the formulation of water-based drilling fluids (WBDF) for drilling operations in any scenario. Due to their high heavy metals content, these additives are toxic and hazardous for any environmental scenario. Deflocculant efficiency of unmodified tannins (UDT) extracted from fruit pods of ''dividivi'' (Caesalpinia coriaria) as an additive for WBDF was assessed. Raw materials for UDT elaboration come from the rural and sustainable exploitation of natural occurring dividivi trees, growing in dry tropical forests in Anzoátegui state (Orinoco Oil Belt, eastern Venezuela). The tannins extract, in the form of dividivi fruit powder, contains 47.0 % of total tannins (hydrolyzable tannins plus condensed tannins), of which 67.4 % corresponds to hydrolyzable tannins. Dividivi tannins in WBDF showed nine (9) times deflocculant efficiency than heavy metals commercial modified tannins. Moreover, commercial modified tannins do not improve their deflocculant efficiency with increased tannin content. Ecotoxicological studies were carried out for WBDF formulations with UDT, using freshwater microalgae Scenedesmus dimorphus as chronic toxicity bioindicator. Toxicity bioassays performed with these microalgae did not show significant effects on its population growth. The EC 50 values resulted in over 100,000 mg L-1 , and these formulations were therefore considered non-toxic. Values of LC 50 obtained this time with Poecilia reticulata, as acute toxicity bioindicator are around 100,000 mg L-1 , with no significant effects on population mortality. Thus, WBDF formulated with UDT can be considered non-toxic formulations for populations of this freshwater fish. From the social perspective, the use of UDT in WBDF fosters organized communities economical activities based on the maintenance of a sustainable supply chain for processing fruits in a quantity enough to obtain three thousand seven hundred fifty kilograms (3750 Kg). The UDT so obtained was used as deflocculant in four (4) oil wells producing excellent performance and relevant savings compared with commercial modified tannin.
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Como parte de una estrategia de conservación del Refugio de Fauna Silvestre Isla de Aves, el cual representa una zona geoestratégica para la República Bolivariana de Venezuela, las instituciones de investigación del país realizan campañas... more
Como parte de una estrategia de conservación del Refugio de Fauna Silvestre Isla de Aves, el cual representa una zona geoestratégica para la República Bolivariana de Venezuela, las instituciones de investigación del país realizan campañas anuales para conocer la biodiversidad de la isla. Uno de los componentes biológicos más importantes es el fitoplancton, ya que, a pesar de que sustenta las redes tróficas pelágicas marinas y es parte esencial del ciclo de los nutrientes, no ha sido estudiado en esta zona, por lo que se presenta en este documento, un inventario del fitoplancton marino. Para ello, se realizaron arrastres con una red cónica de fitoplancton en julio de 2011 y 2012. En laboratorio, se estimó la abundancia por el método de Utermölh, con un microscopio invertido y claves ta-xonómicas. La comunidad estuvo representada por 191 especies distribuidas en 121 diatomeas, 58 dinoflagela-dos, 6 cianobacterias, 3 euglenofitas y 3 silicoflagelados. Finalmente, destacamos que la zona marino costera de la isla se caracteriza por una comunidad fitoplanctónica diversa, con abundancias características de aguas oligotró-ficas de ecosistemas coralinos y procesos de mezcla de la columna de agua. Palabras clave: Caribe venezolano, ecología marina, fito-plancton, Isla de Aves, microalgas.
As part of a conservation strategy for the Wildlife Refuge "Isla de Aves", which represents a geostrategic zone for the Bolivarian Republic of Venezuela, several research institutions conduct studies every year to learn about the island's biodiversity. One of the most important biological components is phytoplankton, since although it sustains marine pelagic trophic networks and is an essential part of the nutrient cycles; it has not been studied in this area, so an inventory of marine phytoplankton was accomplished. Here, we carried out several trawls with a conical phyto-plankton net in July 2011 and July 2012. In the laboratory , abundance was estimated by the Utermölh method, with an inverted microscope and specialized bibliography. The community was represented by 191 species distributed in 121 diatoms, 58 dinoflagellates, 6 cyanobacteria, 3 eugleophytes and 3 silicoflagellates. The coastal marine zone of the island is characterized by a diverse phyto-plankton community, with characteristic abundances of oligotrophic waters of coral ecosystems and processes of mixing the water column.
As part of a conservation strategy for the Wildlife Refuge "Isla de Aves", which represents a geostrategic zone for the Bolivarian Republic of Venezuela, several research institutions conduct studies every year to learn about the island's biodiversity. One of the most important biological components is phytoplankton, since although it sustains marine pelagic trophic networks and is an essential part of the nutrient cycles; it has not been studied in this area, so an inventory of marine phytoplankton was accomplished. Here, we carried out several trawls with a conical phyto-plankton net in July 2011 and July 2012. In the laboratory , abundance was estimated by the Utermölh method, with an inverted microscope and specialized bibliography. The community was represented by 191 species distributed in 121 diatoms, 58 dinoflagellates, 6 cyanobacteria, 3 eugleophytes and 3 silicoflagellates. The coastal marine zone of the island is characterized by a diverse phyto-plankton community, with characteristic abundances of oligotrophic waters of coral ecosystems and processes of mixing the water column.
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Toxic effects of Venezuelan delayed coke were evaluated by using representative organisms from terrestrial, freshwater and marine ecosystems; for instance, Skeletonema costatum (marine micoralgae), Litopenaeus vannamei (shrimp),... more
Toxic effects of Venezuelan delayed coke were evaluated by using representative organisms from terrestrial, freshwater and marine ecosystems; for instance, Skeletonema costatum (marine micoralgae), Litopenaeus vannamei (shrimp), Scenedesmus dimorphus (freshwater microalgae), Poecilia reticulata (freshwater minnow), Medicago sativa (alfalfa seeds) and Eisenia foetida (earthworms). Bioassays were conducted following available international standards for each species by using composed or single samples of venezuelan delayed coke produced by upgrading extra heavy oil from Faja Petrolífera del Orinoco "Hugo Chavez". Values of EC 50 and LC 50 higher than 1,000 mg/L for microalgae, alfalfa seeds and fishes were obtained. For shrimps and earthworms, LC 50 values were higher than 30,000 mg/L and 71% respectively, indicating absent of potential toxicity under evaluated conditions. Low environmental hazards for those ecosystems are envisaged, due to exposure venezuelan petcoke. INDTRODUCTION The Bolivarian Republic of Venezuela is an important oil producer with large reservoirs of heavy and extra heavy oils that need to be upgraded, resulting in products with different market values, among them petroleum coke. Petroleum coke is primarily composed by carbon, with approximately 9-12 % of volatile matter, 0.1 to 0.3 % of ash and 2.5 to 5.5 % of sulfur. Additionally contains some metals such as iron, nickel, vanadium and others. Its chemical composition depends on the feedstock used in delayed coking process [1]. Petroleum coke is produced in large quantities, thus Venezuela is the second largest producer in the world. This product is mainly exported for its use in energy production, but recently, some initiatives propose alternative uses as row material in metallic alloys production, filtering materials and others [2]. Exploitation plans for the Faja Petrolífera de Orinoco "Hugo Chávez", and the world tendency to exploitation of non conventional heavy and extra heavy oil reservoirs with high sulfur content, allow predicting an increasing on petroleum coke production at world scale. Since Venezuelan delayed coke has high sulfur, heavy metals and volatile matter content; is
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Las investigaciones en materia de conservación de la naturaleza muchas veces pasan desapercibidas por la población general, cuyas preocupaciones se enfocan más en resolver sus problemáticas del día a día, quedando estas iniciativas y sus... more
Las investigaciones en materia de conservación de la naturaleza muchas veces pasan desapercibidas por la población general, cuyas preocupaciones se enfocan más en resolver sus problemáticas
del día a día, quedando estas iniciativas y sus resultados dentro de las discusiones y el temario de la academia y la comunidad científica.
Sin embargo, cada habitante de este orbe influye directamente en las condiciones de los diferentes ecosistemas tanto positiva como negativamente– y por ende, la difusión de todas estas aportaciones contribuyen a que entre todos seamos partícipes activos para que nuestro paso por el planeta no cree una cicatriz imborrable.
En este sentido, hemos realizado esta publicación con el fin de hacer llegar a la mayor cantidad posible de personas, los resultados obtenidos durante los dos años de ejecución de Proyecto Orbicella Morrocoy, el cual fue posible gracias al apoyo financiero de la Fundación Segré a través del programa EDGE of Existence de la Sociedad Zoológica de Londres.
El objetivo principal del proyecto fue verificar el estatus de los arrecifes coralinos, en especial de las especies del género Orbicella, luego de 24 años del fatídico evento de mortandad masiva que acabó con hasta el 90% la cobertura coralina del parque, pero no solo se enfocó en ámbito biológico, sino que paralelamente se dirigieron esfuerzos a indagar sobre el conocimiento de los pobladores y usuarios de esta área protegida acerca de los corales, así como a aportarle saberes a los prestadores de servicios de la zona para de esta manera convertirlos en multiplicadores de estos conocimientos y plantar en ellos la semilla de importancia de la conservación de estos invaluables ecosistemas.
No queda más que invitarlos a hacer suyo este material, servirse de el para llevar a otros la conciencia de preservar el planeta para el beneficio del presente y futuro de la vida en la tierra y convertirse en embajadores
de un Morrocoy para disfrutar, no para depredar.
del día a día, quedando estas iniciativas y sus resultados dentro de las discusiones y el temario de la academia y la comunidad científica.
Sin embargo, cada habitante de este orbe influye directamente en las condiciones de los diferentes ecosistemas tanto positiva como negativamente– y por ende, la difusión de todas estas aportaciones contribuyen a que entre todos seamos partícipes activos para que nuestro paso por el planeta no cree una cicatriz imborrable.
En este sentido, hemos realizado esta publicación con el fin de hacer llegar a la mayor cantidad posible de personas, los resultados obtenidos durante los dos años de ejecución de Proyecto Orbicella Morrocoy, el cual fue posible gracias al apoyo financiero de la Fundación Segré a través del programa EDGE of Existence de la Sociedad Zoológica de Londres.
El objetivo principal del proyecto fue verificar el estatus de los arrecifes coralinos, en especial de las especies del género Orbicella, luego de 24 años del fatídico evento de mortandad masiva que acabó con hasta el 90% la cobertura coralina del parque, pero no solo se enfocó en ámbito biológico, sino que paralelamente se dirigieron esfuerzos a indagar sobre el conocimiento de los pobladores y usuarios de esta área protegida acerca de los corales, así como a aportarle saberes a los prestadores de servicios de la zona para de esta manera convertirlos en multiplicadores de estos conocimientos y plantar en ellos la semilla de importancia de la conservación de estos invaluables ecosistemas.
No queda más que invitarlos a hacer suyo este material, servirse de el para llevar a otros la conciencia de preservar el planeta para el beneficio del presente y futuro de la vida en la tierra y convertirse en embajadores
de un Morrocoy para disfrutar, no para depredar.