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Search Results: 1 - 10 of 224119 matches for " Roberto Millán-Nú?ez "
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Changes in the Composition and Abundance of Phytoplankton in a Coastal Lagoon of Baja California, México, during 2011  [PDF]
María Fernanda Gracia-Escobar, Roberto Millán-Nú?ez, Enrique Valenzuela-Espinoza, Adriana González-Silvera, Eduardo Santamaría-del-ángel
Open Journal of Marine Science (OJMS) , 2015, DOI: 10.4236/ojms.2015.52014
Abstract: A time series with weekly sampling was conducted from February 20, to December 16, 2011 at a station in the interior of the San Quintín Bay to estimate seasonal changes in the composition and abundance of phytoplankton. Water temperature was recorded and the upwelling index was calculated for the period. Phytoplankton abundance was estimated and phytoplankton were identified by using an inverted microscope and the CHEMTAX program. There were 16 positive phytoplankton anomalies during the year, but only three were considered to be blooms. The blooms were dominated by diatoms and were recorded in the winter, spring and summer. Different genera composed 80% of the total phytoplankton abundance of each of the blooms. The first bloom consisted of diatoms of the genera Pseudo-nitzschia sp. (15.7%), Skeletonema sp. (14.6%), Eucampia sp. (7%), and Navicula sp. (7%); a haptophyte of the genus Imantonia sp. (13.1%); and dinoflagellates of the genus
Changes in the Abundance and Composition of Phytoplankton in a Coastal Lagoon during Neap-Spring Tide Conditions  [PDF]
María Fernanda Gracia-Escobar, Roberto Millán-Nú?ez, Adriana González-Silvera, Eduardo Santamaría-del-ángel, Víctor F. Camacho-Ibar, Charles C. Trees
Open Journal of Marine Science (OJMS) , 2014, DOI: 10.4236/ojms.2014.42010
Abstract:

The objective of this work was to estimate the changes in abundance and composition of phytoplankton in a coastal lagoon in Baja California, México during neap-spring tide conditions. Sampling was conducted from the 7th to the 16th of October 2004. Surface water was collected at 18 stations distributed across the bay during day time at high tide. Also, a time series was collected at a fixed station; surface water was collected every two hours from 8:00 to 18:00. High temperatures, low salinities and low nutrient concentrations at the oceanic end indicated weak or non upwelling conditions during this period. The phytoplankton community was characterized using an inverted microscope and the chemical taxonomy program CHEMTAX, based on pigment concentration estimated by high performance liquid chromatography (HPLC). The phytoplankton concentration was two times lower during this period than during periods of upwelling in the same year. Cryptophytes and diatoms were the most abundant groups estimated by CHEMTAX. Statistical analyses of the effect of tidal conditions on phytoplankton composition indicate that Zone A is strongly affected by tides, and that tidal effects are lessened at the inner zones. Differences in phytoplankton abundance between zones and between tidal conditions indicate that phytoplankton distribution is patchy in the lagoon.

Macronutrient uptake and carotenoid/chlorophyll a ratio in the dinoflagellate Amphidinium carteri Hulburt, cultured under different nutrient and light conditions
Valenzuela-Espinoza, Enrique;Millán-Nú?ez, Roberto;Santamaría-del-ángel, Eduardo;Trees, Charles C.;
Hidrobiológica , 2011,
Abstract: population growth, macronutrient (,) uptake and carotenoids/chlorophyll a ratio we determined in amphidinium carteri hulburt, cultured under conditions of continuous light (50, 150, 300 and 750 μmol quanta m-2 s-1) and three nutrient concentrations nano3/nah2po4 at 441.5/18.1 μm (low) 883/36.3 μm (medium) and 1766/72.6 μm (high). both nutrient and irradiance had a significant effect (p < 0.05) on cellular abundance during the period of culture, except for the fourth and seventh day for nutrients (p > 0.05). in cultures under low nutrient condition, no- and po4- were almost depleted by the fifth day and in cultures with medium nutrient this condition occurred in the sixth day; whereas, at high nutrient condition the nutrients were not depleted. we concluded that a. carteri had higher growth rates and nutrient consumption at 300 μmol quanta m-2 s-1 during the first five days and in general the effect of nutrients on the pigment ratios was not significant (p > 0.05). however, the average peridinin/chla ratio decreased up to 72% from the lowest and the highest irradiance. the opposite was observed for the average of diadinoxanthin/chla ratio that increased almost two-fold, and the averages dinoxanthin and diatoxanthin to chla ratios that increased from low to high irradiances. the average diatoxanthin/chla ratio at 750 μmol quanta m-2 s-1 increased up to 2.7-fold from the exponential to the stationary phase only in the low and medium nutrient concentration. likewise, the average peridinin, dinoxanthin and diatoxanthin to chla ratios were not significantly different at 50 and 150 μmol quanta m-2 s-1. these results indicate important changes in average carotenoids/chla ratios in a. carteri cultured under different irradiances.
Macronutrient uptake and carotenoid/chlorophyll a ratio in the dinoflagellate Amphidinium carteri Hulburt, cultured under different nutrient and light conditions Consumo de macronutrientes y proporción de carotenoides/clorofila a en el dinoflagelado Amphidinium carteri Hulburt, cultivado bajo diferentes condiciones de luz y nutrientes
Enrique Valenzuela-Espinoza,Roberto Millán-Nú?ez,Eduardo Santamaría-del-ángel,Charles C. Trees
Hidrobiológica , 2011,
Abstract: Population growth, macronutrient (,) uptake and carotenoids/chlorophyll a ratio we determined in Amphidinium carteri Hulburt, cultured under conditions of continuous light (50, 150, 300 and 750 μmol quanta m-2 s-1) and three nutrient concentrations NaNO3/NaH2PO4 at 441.5/18.1 μM (low) 883/36.3 μM (medium) and 1766/72.6 μM (high). Both nutrient and irradiance had a significant effect (p < 0.05) on cellular abundance during the period of culture, except for the fourth and seventh day for nutrients (p > 0.05). In cultures under low nutrient condition, NO- and PO4- were almost depleted by the fifth day and in cultures with medium nutrient this condition occurred in the sixth day; whereas, at high nutrient condition the nutrients were not depleted. We concluded that A. carteri had higher growth rates and nutrient consumption at 300 μmol quanta m-2 s-1 during the first five days and in general the effect of nutrients on the pigment ratios was not significant (p > 0.05). However, the average peridinin/Chla ratio decreased up to 72% from the lowest and the highest irradiance. The opposite was observed for the average of diadinoxanthin/Chla ratio that increased almost two-fold, and the averages dinoxanthin and diatoxanthin to Chla ratios that increased from low to high irradiances. The average diatoxanthin/Chla ratio at 750 μmol quanta m-2 s-1 increased up to 2.7-fold from the exponential to the stationary phase only in the low and medium nutrient concentration. Likewise, the average peridinin, dinoxanthin and diatoxanthin to Chla ratios were not significantly different at 50 and 150 μmol quanta m-2 s-1. These results indicate important changes in average carotenoids/Chla ratios in A. carteri cultured under different irradiances. Se evaluaron el crecimiento poblacional, consumo de macronutrientes (,) y proporción de carotenoides/clorofila a en Amphidinium carteri Hulburt, cultivado durante 7 días, bajo condiciones de luz continua: 50, 150, 300 y 750 μmol quanta m-2 s-1 y tres concentraciones de nutrientes NaNO3/NaH2PO4 (441.5/18.1 μM (bajo); 883/36.3 μM (medio) y 1766/72.6 μM (alto). La abundancia celular fue significativamente afectada (p < 0.05) tanto por el nivel de nutrientes como por la irradianza durante el periodo de cultivo, excepto para el nivel de nutriente en el cuarto y séptimo día. En los cultivos con bajo nutriente, el se agotaron casi totalmente al quinto día, y en cultivos con medio nutriente ocurrió al sexto día; mientras que en alta concentración de nutrientes, éstos no se agotaron. Se concluye que A. carteri tuvo la mayor tasa de crecimiento y
Variability in the Light Absorption Coefficient by Phytoplankton, Non-Algal Particles and Colored Dissolved Organic Matter in the Northern Gulf of California  [PDF]
Stella P. Betancur-Turizo, Adriana G. González-Silvera, Eduardo Santamaría-Del-ángel, Roberto Millán-Nú?ez, Eduardo Millán-Nú?ez, Héctor García-Nava, Víctor M. Godínez, Laura Sánchez-Velasco
Open Journal of Marine Science (OJMS) , 2017, DOI: 10.4236/ojms.2018.81002
Abstract:
Variability of the optical properties of the northern Gulf of California (México) were analyzed for the first time based on six cruises performed from spring to summer (March to September) between 2008 and 2013. The changes observed in the absorption by three seawater components (phytoplankton, detritus and chromophoric dissolved organic matter or CDOM) were analyzed in relation to changes in bio-optical regions and composition of the phytoplankton community (determined based on phytoplankton pigments). Two regions with unique bio-optical characteristics were identified separated by a narrow transition zone: the Upper Gulf of California (UGC) and Northern Gulf of California (NGC). Despite the temporal changes in their spatial distribution they maintained particular characteristic. UGC is characterized by an average Chla of 1.78 mg/m3, the dominance of microphytoplankton (diatoms and dinoflagellates) and a stronger contribution of detritus to total light absorption. NGC is characterized by an average Chla of 0.7 mg/m3 and the predominance of picophytoplankton, characterized by the dominance of zeaxanthin (marker pigment for cyanobacteria) and/or chlorophyll b (marker pigment for green algae), along with a co-dominium by CDOM and phytoplankton to light absorption. Results indicate that Case II waters can be very different when evaluating the individual contribution by phytoplankton, detritus and CDOM to total light absorption what has to be considered for the selection of bio-optical models for each specific region what can also help to a better definition of the related uncertainties.
Avifauna de Campo Morado, Guerrero, México Avifauna of Campo Morado, Guerrero, Mexico
Octavio R. Rojas-Soto,Adán Oliveras de Ita,Roberto Carlos Almazán-Nú?ez,Adolfo G. Navarro-Sigüenza
Revista mexicana de biodiversidad , 2009,
Abstract: Se presenta una lista de 124 especies de aves para la región de Campo Morado, Guerrero, México, con información sobre el estatus estacional, categoría de riesgo y endemismo. Se resaltan 15 registros sobresalientes, ya sea porque son nuevos para el estado, o porque amplían su distribución geográfica y/o modifican su distribución estacional conocida. Además se discute la importancia de la localidad dentro de la cuenca del río Balsas. We report a list of 124 bird species from Campo Morado, Guerrero, Mexico, with information on seasonality, risk categories, and endemism. Fifteen records are noteworthy, as they are new state records, expand significantly their known geographical distribution, and/or modify their seasonal status within the area. We also highlight the importance of the study area within the Balsas River Basin.
Información adicional sobre la avifauna de la Sierra Norte de Guerrero, México
ALMAZáN-Nú?EZ, R. Carlos;
Acta zoológica mexicana , 2009,
Abstract: a systematic list of birds recently observed at the sierra norte, guerrero, mexico is presented. the information was gathered during field work carried out from july 2001 to september 2002 and october 2007. 101 species belonging in 13 orders and 34 families were observed. i reported 21 additional records for the avifauna of the sierra norte, of which some species have been previously mentioned for this region, but there is not confirmation of its presence with precise dates and localities. the sierra norte richness increased to 175 species of birds; however, the magnitude of species increment suggests the necessity of more inventories for a more precise knowledge on species' distribution.
INFORMACIóN ADICIONAL SOBRE LA AVIFAUNA DE LA SIERRA NORTE DE GUERRERO, MéXICO
R. Carlos ALMAZáN-Nú?EZ
Acta zoológica mexicana , 2009,
Abstract: Se presenta una lista sistemática de las aves registradas en la Sierra Norte de Guerrero, México. La información fue recopilada durante el trabajo de campo llevado a cabo durante Julio de 2001 a Septiembre de 2002 y Octubre de 2007. Se registró un total de 101 especies pertenecientes a 13 órdenes y 34 familias. Se reportan 21 registros adicionales para la avifauna de la Sierra Norte, de los cuales algunas especies habían sido previamente mencionadas para esta región, pero no existía confirmación de su presencia con fechas y localidades precisas. La riqueza de aves de la Sierra Norte aumentó a 175 especies; sin embargo, la cantidad de especies incrementadas sugiere la necesidad de inventarios detallados para un conocimiento más preciso sobre la distribución de las especies.
Respuesta
Millán Nú?ez Roberto
Ciencias marinas , 2005,
Abstract:
Avifauna de Campo Morado, Guerrero, México
Rojas-Soto, Octavio R.;Oliveras de Ita, Adán;Almazán-Nú?ez, Roberto Carlos;Navarro-Sigüenza, Adolfo G.;Sánchez-González, Luis Antonio;
Revista mexicana de biodiversidad , 2009,
Abstract: we report a list of 124 bird species from campo morado, guerrero, mexico, with information on seasonality, risk categories, and endemism. fifteen records are noteworthy, as they are new state records, expand significantly their known geographical distribution, and/or modify their seasonal status within the area. we also highlight the importance of the study area within the balsas river basin.
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