Trends in the size of mesozooplankton during the last 25 years at A Coruña (N Spain)

Temporal changes in the mean individual size and in the abundance of taxonomical groups of different size of mesozooplankton (200-2000 µm) were investigated in samples collected in the shelf waters of A Coruña (N Spain) since 1988. An overall decreasing trend in the average size of individuals, indicated by the biomass (dry weight) to abundance ratio was observed. Most of this decrease can be attributed to the increase in the dominance of copepods of small size ( 1 mm) were found. Indeed, some species of large size showed increasing trends in abundance during the study period. Nevertheless these trends were small at linear scales and most species did not show significant linear trends during the study period. The observed trends in zooplankton were related to weak changes in sea surface temperature and upwelling intensity during the studied period. This suggests that the effects of the general warming of the surface ocean on plankton are weakened in regions of coastal upwelling.IEO (RADIALES

COMPOSICION y ABUNDANCIA DEL MICROZOOPLANCTON EN LA PLATAFORMA CONTINENTAL GALLEGA

Se ha estudiado la composición y abundancia del microzooplancton (20-200 mm) en dos estratos de profundidad (0-15 y 15-30 m) en un total de 16 estaciones de muestreo situadas sobre la plataforma continental gallega, durante tres campañas oceanográficas realizadas en verano, otoño y primavera. Los estadios larvarios de organismos holoplanctónicos y meroplanctónicos dominan en la comunidad del microzooplancton. Entre ellos destacan las larvas nauplius de copépodo, cuya abundancia relativa es mayor en primavera (87%) que en verano (40%) y otoño (52%), y las larvas de lamelibranquio que son más abundantes en verano (13%) y otoño (10%) que en primavera (2.5%).Los valores extremos de las abundancias del microzooplancton fueron de 1 y 82 ind 1-1• Las abundancias medias en primavera y verano fueron de 25 y 20 ind 1-1 respectivamente, mientras que en otoño la media fue de 8 ind 1-1• Las larvas nauplius no presentan una distribución de abundancias localizada en una zona determinada de la plataforma continental, en cambio, las larvas de lamelibranquio son más abundantes en las estaciones situadas frente alas Rías de Vigo y Arosa que en las situadas frente a la Ría de Muros, Cabo Vilano y La Coruña.Postprin

Zooplankton composition and distribution off the coast of Galicia, Spain

During June and September 1984, zooplankton samples were collected with other hydrographic and biological data along the Galician coast (NW of Spain). In June copepods contributed -60% to the total zooplankton community, with larvaceans, siphonophores and cladocerans also abundant. In September >90% of the zooplankton sampled were copepods. The dominant species of copepods in both June and September were Acartia e/ausi, Paracalanus parvus and Temora longicornis. The meroplankton was dominated by echinoderms, bryozoans, barnacle larvae and bivalve larvae. In June the average zooplankton biomass was 31.08 mg e m-3; the September average was 41.69 mg e m-3 The relationship between the slopes of the regression equations (biomass versus abundance) suggests that the zooplankton assemblage in June was composed by larger animals than in September. The major concentration of zooplankton was between O and SO m, with both June and September daytime surface samples having 6-7 times the amount of organisms than the lower water column (50-100 m). There were no distinct differences in total zooplankton abundances at the inshore and offshore stations; however, the inshore stations often had a higher percentage of meroplankton than the offshore stations. In June zooplankton abundance at the northern transects and the western transects was similar. In September there were greater concentrations of zooplankton in the western Galician shelf as compared with the northern shelf. These differences in the horizontal distribution of the zooplankton were related to upwelling events.Postprin

Diversity and abundance of planktonic communities in the deep waters off the galician coast (NW Spain)

Comunicación oralPlanktonic communities play pivotal roles within marine ecosystems, affecting their structure, functioning and services. Although they have been extensively studied in the epipelagic ocean, the knowledge about these communities in the dark ocean is rather short. In this study, we explored patterns of abundance and biomass of a wide variety of taxonomic groups from the prokaryotes to mesozooplankton in the epi-, meso- and bathypelagic waters off the Galician coast. As expected, ciliate and zooplankton abundances are depleted in the bathypelagic waters relative to abundances of prokaryotes and nanoflagellates. The rate of decrease of zooplankton biomass with depth is twice as that of prokaryotes and nanoflagellates, indicating that relative contribution of mesozooplancton to the total plankton biomass decreases with depth. Overall, the diversity of prokaryotes in the dark ocean is almost as high as in the epipelagic layer, although the phylotypes are different. The major fraction of epipelagic ciliates belongs to alloricate genera, whereas tintinnids dominate the deep ciliate populations. Small copepods were dominant in the epi- and meso-pelagic zone. By contrast, foraminiferans, big copepods and myctophic fishes were more abundant in the deep ocean

Stable nitrogen isotope studies of the pelagic food web on the Atlantic shelf of the Iberian Peninsula

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Recent changes in the pelagic ecosystem of the Iberian Atlantic in the context of multidecadal variability

Trends in ecosystem variables of the Eastern North Atlantic shelf near the Iberian Peninsula were analysed in relation to regional climate and oceanographic variability. In addition, detailed changes in oceanographic properties (surface temperature, upwelling and poleward current activity) and biological components (plankton and pelagic consumers) in the period 1989-2005 were compared with the main trends and multidecadal periods observed in time series dating back to 1950. In contrast to previous studies, the North Atlantic Oscillation did not appear as the main influence in the climate of the North Iberian region, while East-West and subtropical gradients were the dominant modes. Climatic oscillations at decadal scales were paralleled by similar oscillations in oceanographic and biological variables, but the latter appeared weakly related to climate. Time- lags of up to 5 years in the biological response may partly explain these relationships. The main planktivorous fish species (sardine and anchovy) alternate in periods of 10-15 years of relative dominance, in synchrony with equivalent species around the world. In contrast, plankton cycles appear greatly modified after 1990 in coincidence with shifts in climatic and oceanographic variables. Subregional variability indicated divergent trends in biological variables, particularly the zooplankton increase off A Coruña and the decrease in the Bay of Biscay since 1990. Such divergences are related to direct and indirect effects of global changes in this transitional upwelling region

Vertical variability of trophic positions of zooplankton in the deep Ocean

Zooplankton plays a key role in oceanic ecosystems. However, the trophic ecology of organisms in deep layers of the ocean is poorly known. In this study we analyze the variability of trophic positions of zooplankton collected across three ocean basins in the epi-, meso and bathypelagic domains. Stable carbon and nitrogen isotopes were used as indicators of the sources of nutrients and positions within the food web. The enrichment in heavy nitrogen isotopes with depth and the correlation between surface and deep samples revealed that deep zooplankton was supported by local epipelagic production, subsequently processed through the water column. In addition the nitrogen isotope enrichment of carnivores vs. omnivores was consistent across ocean biomes and water layers, suggesting a similar trophic structure of the pelagic food web in the deep ocean despite variations in the nitrogen sources. Siphonofora, Chaetognata and Myctophida were the top predators while Calanoid Copepoda and Mysidacea displayed the lowest trophic positions. In contrast, carbon isotopes did not show significant variations with depth or trophic groups implying low influence of coastal production in deep ocean food webs

Zooplancton

La influencia de factores climáticos y oceanográficos sobre el zooplancton de la región norte y noroeste de la Península Ibérica fue analizada mediante cinco series temporales de observaciones de abundancia, composición específica y biomasa. Las series incluyeron la región oceánica próxima, representada por el área estándar F4 del Continuous Plankton Recorder entre 1960 y 2006, así como series costeras de Galicia (Vigo y A Coruña) y el mar Cantábrico (Cudillero, Gijón, Santander), muestreadas desde la década de 1990. En el océano se detectó un incremento interanual en biomasa y número de especies de copépodos entre 1960 y 1986, mientras que en la costa se detectaron incrementos en la abundancia y biomasa de algunas especies en Vigo y disminuciones de otras en A Coruña y Santander en los últimos años. Ninguna de las series del Cantábrico mostró tendencias ni ciclos en los valores interanuales de biomasa durante el periodo de observación. El plancton gelatinoso (medusas y tunicados) no mostró un patrón común a escalas locales, con incrementos en las medusas en Vigo y en los tunicados en A Coruña. La influencia climática y oceanográfica sobre este tipo de zooplancton parece resultar de modificar la proporción entre copépodos y plancton gelatinoso a partir de un efecto más directo del clima y las condiciones oceanográficas sobre los primeros. En Galicia el número y diversidad de especies de copépodos y su biomasa se incrementaron con la temperatura mientras que en el mar Cantábrico sólo se incrementaron en abundancia y ocupación espacial las especies de aguas cálidas (como Temora stylifera) mientras que las especies oportunistas típicas de afloramiento (como Acartia clausi) disminuyeron. La modulación local de los efectos del clima y del afloramiento sobre el zooplancton de la región sugiere la existencia de interacciones no lineales a largo plazo que favorecerían el mantenimiento e incluso el incremento de biomasa y diversidad de zooplancton a pesar de la tendencia a la disminución en el afloramiento observada en las últimas décadas.The influence of climatic and oceanographic factors on zooplankton in the northern and northwestern region of the Iberian Peninsula was analysed using five time-series of abundance, species composition and biomass. The series included the nearby ocean region, represented by the standard area F4 of the Continuous Plankton Recorder between 1960 and 2006, as well as coastal series from Galicia (Vigo and A Coruña) and the Mar Cantábrico (Cudillero, Gijón and Santander) sampled from the 1990s. An increase in biomass and species number of copepod species was detected in the oceanic region between 1960 and 1986. In the coast, however, the abundance and biomass of some species also increased in Vigo but decreased for other species in A Coruña and Santander in recent years. No long term trends or cycles were detected in any of the Mar Cantábrico biomass series. Gelatinous plankton (medusae and tunicates) did not show any common trend at local scales, having increased medusae in Vigo and tunicates in A Coruña. Climate and oceanographic factors appear to influence the ratio between copepods and gelatinous zooplankton through a larger effect of the environment on copepods. Temperature increased the number and diversity of copepod species in Galicia whereas in the Mar Cantábrico only warm tolerant species (as Temora stylifera) increased in abundance and spatial distribution while opportunistic species typical of upwelling waters (as Acartia clausi) decreased. Local modulation of climate and upwelling effects on zooplankton suggest non-lineal interactions favouring the sustaining and even increase of zooplankton biomass and diversity despite the decadal decrease of upwelling in this region

Taxonomic versus trophic structure of mesozooplankton: a seasonal study of species succession and stable carbon and nitrogen isotopes in a coastal upwelling ecosystem

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