Resumen. Los copépodos, como uno de los principales grupos que componen el zooplancton marino, juegan un papel importante por su posición en la red trófica. Se evaluó la biomasa de copépodos en un vórtice ciclónico durante 2 estaciones climáticas contrastantes en la bahía de La Paz, al sur del golfo de California, la cual se caracteriza por una alta productividad biológica. Durante 2 campañas oceanográficas en invierno de 2006 y verano de 2009, se determinó la estructura física de la columna de agua mediante un CTD y se recolectaron muestras de zooplancton mediante arrastres oblicuos. Se utilizaron datos de satélite para visualizar los patrones de distribución de clorofila a (Cla). Los resultados mostraron un vórtice ciclónico en ambas estaciones, con un diámetro de ~25 km y velocidades geostróficas >50 cm·s-1 en su periferia, con elevada Cla (~3 mg·m-3 en invierno). La máxima biomasa de calanoides ocurrió en invierno, con hasta 6.6 mg·100 m-3 en el oeste de la bahía, cerca de la costa; además, su distribución coincidió con el patrón de Cla y circulación, ya que formó un anillo siguiendo la periferia del vórtice, con un segundo pico cerca de la conexión con el golfo. Los valores medios de biomasa de copépodos mostraron un patrón de alternancia calanoides-ciclopoides entre invierno y verano dentro del vórtice ciclónico, con más biomasa de calanoides que ciclopoides en invierno y lo contrario en verano. Los resultados resaltan el impacto del vórtice en el ecosistema planctónico a través de su influencia sobre las condiciones hidrográficas en la columna de agua. Otros factores, como las interacciones ecológicas, la dinámica poblacional y los hábitos alimenticios, también pueden jugar un papel importante. El comportamiento alimentario es afectado por altas concentraciones de Cla, que representan una fuente de alimento para copépodos observados alrededor del vórtice.

Abstract. As one of the main groups comprising marine zooplankton, copepods play an important role due to their position in the trophic web. We assessed the copepod biomass in a cyclonic eddy during 2 contrasting seasons in the Bay of La Paz, southern Gulf of California, which is characterized by high biological productivity. Two oceanographic expeditions took place in the winter of 2006 and the summer of 2009; a CTD probe was used to determine the physical structure of the water column, and oblique zooplankton hauls collected zooplankton samples. Satellite data were used to visualize the chlorophyll a (Chla) distribution patterns. The results showed a well-defined cyclonic eddy in both seasons, with a diameter of ~25 km and geostrophic velocities >50 cm·s-1 in its periphery. At the edges of the eddy, Chla was high, reaching ~3 mg·m-3 in winter. The maximum calanoid copepod biomass occurred in winter, reaching 6.6 mg·100 m-3 in the western bay close to the coast; moreover, their distribution corresponded well with the Chla and circulation patterns, forming a belt shape following the periphery of the eddy, with a second peak close to the connection with the gulf. The mean values of copepod biomass exhibited a pattern with alternating calanoids-cyclopoids between winter and summer within the cyclonic eddy, with calanoid biomass higher than cyclopoid biomass in winter, which was the opposite of summer. The results highlight the impacts of the eddy on the planktonic ecosystem through its influence on the hydrographic conditions in the water column. Other factors, such as ecological interactions, population dynamics, and feeding habits, may also play a role. Feeding behavior is affected by the high concentrations of Chla, which represent a source of food for copepods observed around the eddy.

Resumen Se analizó la abundancia, diversidad y distribución de eufáusidos y su relación con procesos hidrodinámicos entre febrero de 2011 y octubre de 2012 en el cañón de Campeche, sur del golfo de México. Se muestrearon un total de 55 estaciones para las cuales se utilizaron redes de arrastre horizontales para capturar organismos de zooplancton y variables ambientales (temperatura, salinidad y oxígeno). Los niveles de fluorescencia del fitoplancton se registraron a diferentes profundidades. Se identificaron 24 especies de eufáusidos de los géneros Euphausia, Nematobrachion, Nematoscelis, Stylocheiron y Thysanopoda. Stylocheiron carinatum fue abundante en febrero y octubre; la etapa de furcilia fue siempre la más abundante. El análisis batimétrico permitió la regionalización en 4 zonas; la zona III (eje y cabecera del cañón) tuvo mayor diversidad de eufáusidos a 100 y 200 m de profundidad con 2.14 bits Ind-1 en febrero y 1.99 bits Ind-1 en octubre. La distribución espaciotemporal de los eufáusidos fue heterogénea en cuerpos de agua con temperaturas entre 15° y 22 °C y bajas concentraciones de oxígeno, que se distribuyeron fuera de las concentraciones máximas de clorofila-a (Chl-a) (2,127 mg m-3), y con afinidad por los frentes geostróficos entre los remolinos ciclónicos y anticiclónicos.

Abstract We analyzed the abundance, diversity, and distribution of euphausiids and their relationship with hydrodynamic processes from February 2011 to October 2012 in the Campeche Canyon in the southern Gulf of Mexico. Sampling was conducted at 55 oceanographic stations and zooplankton were captured using horizontal trawls. Environmental variables (temperature, salinity, and oxygen) and phytoplankton fluorescence were recorded at different depths. Twenty-four species of euphausiids representing the genera Euphausia, Nematobrachion, Nematoscelis, Stylocheiron, and Thysanopoda were identified. Stylocheiron carinatum was abundant in February and October, with the furcilia stage always the dominant one. Differences were observed among the 4 zones identified based on the bathymetric criteria; zone III (axis and head of the canyon) presented the highest diversity of euphausiids between 100 and 200 m with 2.14 bits Ind-1 in February and 1.99 bits Ind-1 in October. The spatial-temporal distribution of euphausiids was heterogeneous in water bodies with temperatures between 15 and 22 °C and low dissolved oxygen concentrations, which were distributed outside the maximum concentrations of chlorophyll-a (2,127 mg m-3) and had an affinity for the frontal regions between cyclonic and anticyclonic eddies.

ABSTRACT Marine zooplankton play key roles in the transfer of energy to higher trophic levels and the removal of CO2 from the atmosphere through the sedimentation of inorganic and organic carbon compounds included in their fecal pellets. Therefore, differences in the zooplankton groups driven by climate variations could influence the biogeochemical cycles at large oceanic scales. As a contribution to this topic, we analyzed the zooplankton groups in the Bay of La Paz, Gulf of California, Mexico, a highly dynamic basin characterized by its high biological productivity. We used information gathered during multidisciplinary research cruises in the summers of 2008 and 2009. The results showed differences in the hydrographic parameters between both summers, with a higher temperature recorded in 2009. The zooplankton groups showed that the calanoid copepods were the most abundant; however, there were important differences in the relative abundance of the rest of the analyzed groups as an effect of the temperature distribution along the study area, which was confirmed by multivariate statistical methods. These temperature changes were associated with increased gelatinous zooplankton (Cnidaria, Chaetognatha, Appendicularia, and Ctenophora) in 2009 in a region where the temperature was higher, possibly as a result of changes in food (phytoplankton) availability.

Abstract: Information on selected bio-optical properties and primary production values of the waters of the Bay of La Paz, southern Gulf of California, is reported during June 2004, a region characterized to have very rich biodiversity, including endemic and endangered species, with high ecological relevance. In-situ measurements of natural fluorescence and photosynthetically available radiation (PAR) enabled the subsequent calculation of the incident irradiance (E 0 ), the light extinction coefficient (k), compensation depth (Z c ) and critical depth (Z cr ). The results suggest the presence of light propitious conditions for phytoplankton community growth and net primary production, which are highly significant for the potential development of models of light penetration, ocean color, primary productivity, and analyses of organic carbon energy flow.

ABSTRACT The optical properties of the water column have a significant influence on phytoplankton growth. In this work, we report selected optical property values of the waters of two regions in the southern Gulf of Mexico. Measurements of natural fluorescence and photosynthetically available radiation (PAR) were made during a multidisciplinary research cruise, enabling the subsequent calculation of the light extinction coefficient (k), compensation depth (Zc), critical depth (Zcr), and compensation light intensity (Ec). The results revealed an interesting contrast between the two areas but also indicated the presence of optimal conditions for phytoplankton community growth and net primary production. These data, as reported here, could set the stage for the development of bio-optical models of light penetration, ocean color and primary productivity in the region, as well as for future analyses of organic carbon energy flow. However, many more studies are required to establish the possible seasonal variations in these parameters, which could be linked to the wide variability of the region.

Este estudo analisou o papel das forçantes barotrópica e baroclínicadas marés na agregação e dispersão do ictioplâncton no sul do Golfo do México. A amostragem do ictioplâncton e o cálculo dos parâmetros hidrográficos foram realizados durante Setembro de 1992 num ponto fixo de 180 m de profundidade, perto da quebra de plataforma (19º32'N - 92º38.5'W). Uma amostragem de tipo yoyo com CTD foi realizada durante 24 h e amostras biológicas foram tomadas a cada 2 h. Estas medidas foram combinadas com dados de densidade da água e velocidade obtidas de simulações do modelo do Sistema Regional de Modelo dos Oceanos (ROMS). Uma termoclina e duas haloclinas foram detectadas. O número de Froude aumentou com uma defasagem de 2 h com relação à maré barotrópica, sugerindo a existência de uma maré baroclínica. A agregação e a dispersão do ictioplancton mostraram variações verticais tanto em abundância quanto no número de taxa e larvas, com defasagem de 5 h em relação à máxima maré barotrópica e esteve em fase com a oscilação da termoclina. A oscilação vertical foi atribuída a um controle hidráulico forçado pela maré interna.

The role of vertical barotropic and baroclinic tidal forcing in the aggregation and dispersion of ichthyoplankton in the Southern Gulf of Mexico was analyzed in this study. Samplings of ichthyoplankton and the determination of hydrographic parameters were performed during September 1992 at a single point of 180 m depth, near the shelf break (19º32'N - 92º38.5'W). A 24 h CTD yo-yoing casting and biological samples were taken every 2 h and these measurements were combined with water velocity and density simulations from the Regional Ocean Model System (ROMS). One thermocline and two haloclines were depicted. The Froude number increased with a 2 h lag with respect to the maximal barotropic tide, suggesting the existence of a baroclinic tide. Aggregation and dispersion of the ichthyoplankton showed vertical oscillations in the abundance and the numbers of taxa and larvae with a 5 h lag with respect to the maximal barotropic tide and were in phase with the thermocline oscillation. The vertical oscillation was attributed to a hydraulic control forced by the internal tide.

A variabilidade intramaré, o fluxo de salinidade, a clorofila-a e material em suspensão foram avaliados em um canal superficial de maré tropical em uma lagoa costeira ao oeste do Golfo do México. Os dados de velocidade, temperatura e condutividade foram usados para cálculo dos fluxos durante três ciclos de velocidades das marés (tvc) sob condições extremas de descarga. A Clorofila-a e material em suspensão foram determinados abaixo em subsuperfície. Em ambas as estações (seca e chuvosa), o fluxo dominante foi durante o refluxo e com duração maior durante o fluxo de entrada. A máxima velocidade encontrada foi 0.30 m s-1 em maio (estação seca) e 0.60 m s-1 em setembro (estação chuvosa). Durante a época seca foram exportadas 7.56 Kg de clorofila-a, enquanto a importação foi de 3.32 Kg. Durante a temporada de chuva a média exportada (47.3 Kg) foi seis vezes maior que a importada (7.93 Kg). A concentração media de material em suspensão exportado durante a época de chuvas (111.3 Kg) foi 4.6 vezes maior (859 Kg) que durante estação de seca (184.7 Kg). A assimetria das marés é um mecanismo efetivo de transporte, introduzindo no rio águas relativamente quentes e mais salinas através do canal de maré.

Intratidal variability and flux of salt, chlorophyll-a and suspended materials were evaluated in a shallow tropical tidal channel linking a coastal lagoon to the western Gulf of Mexico. Velocity, temperature and conductivity were used to calculate the fluxes. Data were recorded during three tidal velocity cycles (tvc) under extreme river discharge conditions. Chlorophyll-a and suspended materials were determined below the surface. In both seasons (dry and rainy), the flow was ebb-dominated and with longer duration than when in flood. Maximum current velocities were 0.30 m s-1 in May (dry season) and 0.60 m s-1 in September (rainy season). In the dry season the mean chlorophyll-a export was of 7.56 Kg over tvc while the import was of 3.32 Kg. In the rainy season mean export (47.3 Kg) was 6 times greater than the import (7.93 Kg over tvc). Phytoplankton was dominated by organisms of marine origin. The mean of exported, suspended materials in the rainy season (111.3 Kg) was 4.6 times greater (859 Kg) than that in the dry season (184.7 Kg over tvc). Tidal velocity asymmetry is an effective mechanism of exportation, introducing relatively warm and saltier water into the river through the tidal channel.

We report the presence of two individuals of Crypturellus cinnamomeus, and provide photographic evidence of such records in Monumento Natural Cerro de la Silla and Sierra "Cerro de la Silla", which are natural protected areas at federal and state level respectively; both are part of the biological corridor of the Sierra Madre Oriental for Neotropical species. The information that we provide here about the records registered in May 27 and July 5 of 2011 is important because it constitutes a distributional range extension of a species protected under the category "subject to special concern" (Pr) by Mexican Laws (NOM-059-SEMARNAT-2010) and also because the species is recorded for the first time on both slopes of the Sierra de la Silla.

Reportamos la presencia de dos individuos de Crypturellus cinnamomeus y proporcionamos evidencia fotográfica de dichos registros en el Monumento Natural Cerro de la Silla y Sierra "Cerro de la Silla"; áreas naturales protegidas de competencia federal y estatal respectivamente que forman parte del corredor biológico de la Sierra Madre Oriental para especies neotropicales. La importancia de la información que proporcionamos aquí sobre los registros realizados el 27 de mayo y 5 de julio de 2011 radica en que constituyen una ampliación en la distribución de esta especie sujeta a protección especial (Pr) según la NOM-059-SEMARNAT-2010, y a que se registra por primera vez en ambas vertientes del macizo montañoso Sierra de la Silla.