Luis Troccoli

Influence of environmental variables and reproduction on the gonadal fatty acid profile of tropical scallop Nodipecten nodosus.

We examined the influence of the reproductive cycle and environmental variables on the gonadal fatty acid profile in the tropical scallop Nodipecten nodosus. Individuals from a natural population in north-eastern Venezuela (Caribbean Sea) were sampled monthly during one year. The gonadosomatic index (GSI) and a visual assessment of gonadic status are also reported. The environmental conditions characterized by chlorophyll a, temperature and seston concentration were measured in parallel. The highest reproductive activity, with a GSI of 13-18%, was observed from November 2003 to April 2004, and a decrease in GSI, taken as an indication of three spawning periods, was recorded in October, January and May-June. The GSI was 5-8% outside these intervals. A similar trend was observed in maturity stage frequency. Statistical analysis (MDS-ANOSIM) established two different periods; one dominated by upwelling (January to July) and the other characteristic of non-upwelling conditions (August to December). The fatty acids 16:0, 22:6n-3, 20:5n-3 and 16:1n-7 were responsible for the differences between two periods and explained 50% of the observed variance. Accordingly, during the upwelling period, fatty acids such as 22:6n-3 were positively correlated with temperature, organic seston and bivalves in the spent sexual stage and inversely related to the GSI. Furthermore, individuals in the ripe sexual stage were positively related to 20:5n-3 and 18:3n-3, whereas chlorophyll a was directly related to 18:1n-7 and 16:1n-7. In the non-upwelling period, a significant and positive correlation was obtained between fatty acids such as 20:5n-3 and 22:6n-3 and the GSI and the bivalves in the ripe sexual stage, whereas these acids were inversely correlated with the spent sexual stage. In addition, chlorophyll a was positively related to 18:1n-9 and 18:2n-6. Changes in the gonadal fatty acid profile of N. nodosus were influenced by the environmental variables (exogenous factors) during the upwelling and non-upwelling periods and by reproductions (endogenous factors).

Microbial activity in surface sediments of Chacopata-Bocaripo lagoon axis, Sucre State, Venezuela.

The aim of this work was to evaluate the microbial activity of the surface sediments (0-10 cm) of the Chacopata-Bocaripo lagoon axis (Ch-BLA) through microbiological parameters: microbial biomass (Cmic) dehydrogenase activity (DHS), fluorescein diacetate hydrolysis (HFDA), arginine ammonification (AA) and biochemical parameters: phosphatase (PHa) and urease (URa) activity. They were determined during transition (July 2010) and upwelling (March 2011) periods. Total organic carbon (TOC) did not vary significantly (p⩾0.05) between climatic periods. All the parameters studied were higher in upwelling season: Cmic (191.79 mg Cmic kg(-1)), DHS (228.70 μg TFF g(-1) 24 h(-1)), HFDA (204.09 μg fluorescein g(-1) 24 h(-1)), AA (13.09 μg NH4-N g(-1) h(-1)), PHa (132.31 μg pNF g(-1) h(-1)), URa (12.90 μg NH4-N g(-1) h(-1)). They appear to be controlled by the availability and quality of nutrients in each climatic period, and were useful tools for evaluating changes in microbial activity in marine sediments.

Variación estacional y vertical de la biomasa del macrozooplancton en la bahía de Mochima, Estado Sucre - Venezuela, durante 1997 - 1998

The role of macrozooplankton in Mochima Bay was studied examining its biomass and its relationships with some environmental parameters during 1997 and 1998. ...

Seasonal change in macromolecular support of reproduction of the tropical scallop Nodipecten nodosus : evidence from lipid content and fatty acid profiles of four tissues

Departement deBiologie, Universite ´Laval, Quebec, P.Q. Canada G1K 7P4Changes in total lipids and fatty acid profiles (FAPs) of gonad, digestive gland, mantle and muscle of the tropical scallopNodipectennodosuswereexaminedduringcoastalupwellingandupwellingrelaxationperiods.Totallipidsweremostabun-dantindigestivegland,andintermediateinfemalegonad.Multidimensionalscalinganalysisofsimilarities(MDS-ANOSIM)andsimilaritypercentageanalyses(SIMPER)revealedsignificantchangesofFAPsofthefourtissuesduringtheupwellingandupwelling relaxation periods. During both periods, SIMPER analysis revealed an internal similarity index greater than 90%for FAP of each tissue. However, during upwelling the gonad-FAP showed a lower dissimilarity index with the digestivegland-FAP (10), than with muscle-FAP (11) or mantle-FAP (13). In general, during upwelling, the fatty acids 16:0, 18:0,16:1 n-7, 20:5n-3, 22:6n-3 and total PUFAn-3 explained 42 to 63% of variance between tissues; during upwelling relaxation,these fatty acids together with 14:0 and 18:1 n-7, explained 46 to 64% of variance. During upwelling period, MDS-ANOSIMshowed a close association between FAP of digestive gland and gonad, suggesting a rapid transfer of fatty acids between thesetissues, and consequently, that N. nodosus follows an opportunistic strategy during this period. In contrast, during upwellingrelaxation,theslowandcontinuousfallintotallipidcontentsofdigestivegland(SeptembertoNovember)andtheprogressivereduction of MDS distances between FAPs of digestive gland and gonad (August until November), suggest a gradual transferof lipids from digestive gland to gonad to support the gonad development observed during this period. This suggests thatN. nodosus switches to a conservative strategy during the upwelling relaxation period.Keywords: bivalve, Caribbean Sea, energy reserves, gonad, upwelling season

The Scientific Legacy of the CARIACO Ocean Time-Series Program

The CARIACO (Carbon Retention in a Colored Ocean) Ocean Time-Series Program station, located at 10.50°N, 64.66°W, observed biogeochemical and ecological processes in the Cariaco Basin of the southwestern Caribbean Sea from November 1995 to January 2017. The program completed 232 monthly core cruises, 40 sediment trap deployment cruises, and 40 microbiogeochemical process cruises. Upwelling along the southern Caribbean Sea occurs from approximately November to August. High biological productivity (320-628 g C m-2 y-1) leads to large vertical fluxes of particulate organic matter, but only approximately 9-10 g C m-2 y-1 fall to the bottom sediments (∼1-3% of primary production). A diverse community of heterotrophic and chemoautotrophic microorganisms, viruses, and protozoa thrives within the oxic-anoxic interface. A decrease in upwelling intensity from approximately 2003 to 2013 and the simultaneous overfishing of sardines in the region led to diminished phytoplankton bloom intensities, increased phytoplankton diversity, and increased zooplankton densities. The deepest waters of the Cariaco Basin exhibited long-term positive trends in temperature, salinity, hydrogen sulfide, ammonia, phosphate, methane, and silica. Earthquakes and coastal flooding also resulted in the delivery of sediment to the seafloor. The programs legacy includes climate-quality data from suboxic and anoxic habitats and lasting relationships between international researchers.

Densidad, biomasa y composición del zooplancton, en el estrato superficial de la cuenca de Cariaco, Venezuela

Resumen es: Con la finalidad de entender los procesos que determinan los cambios en la composicion y abundancia del zooplancton en la estacion de series de tiempo CA...

BIOMASA, DENSIDAD Y COMPOSICION ZOOPLANCTONICA DE LA BAHIA DE MOCHIMA, VENEZUELA

La biomasa, densidad y composicion del zooplancton de la bahia de Mochima fueron estudiadas durante 1998. Las muestras fueron recolectadas mensualmente en la entrada de la bahia (estacion A) y en la parte interna (estacion B) entre enero y diciembre de 1998. En cada estacion se realizaron calados oblicuos con una malla estandar de 300 micras y 0,25 m de diametro de boca a 0-5 y 10-15 m y a una velocidad de dos nudos durante 10 min. El indice de surgencia se calculo a partir de los datos de vientos. Se midio salinidad, temperatura del agua, concentracion de oxigeno disuelto, concentracion de clorofila a, biomasa y densidad del zooplancton; ademas se identificaron los organismos, en lo posible hasta especie. Los perfiles de temperatura mostraron un mayor tiempo de permanencia de aguas calidas superficiales en la estacion mas interna. Los valores mas altos de densidad zooplanctonica (4066 ind/m3) se registraron en el periodo febrero - mayo y luego los valores fueron relativamente bajos (< 200 ind/m3) entre junio-julio para ambas estaciones y entre octubre - diciembre para la estacion A. La mayor densidad zooplanctonica se midio en la estacion B y en la capa 10 - 15m. Cualitativamente, la comunidad zooplanctonica de las dos estaciones fue muy similar. Se identificaron 18 grupos zooplanctonicos, destacando por su abundancia relativa los copepodos, apendiculados, nauplios de balanidos y cladoceros en ambas estaciones. Estos ultimos dominaron entre los meses de julio - septiembre (periodo de aguas calidas) en las aguas internas de la bahia. La relacion entre el indice de surgencia y la temperatura del agua con la variacion en la densidad y composicion zooplanctonica reflejo una fuerte influencia de los factores abioticos