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Isla E.,CSIC - Institute of Marine Sciences | Sane E.,CSIC - Institute of Marine Sciences | Homs P.,CSIC - Institute of Marine Sciences | Teixido N.,CSIC - Institute of Marine Sciences | Escribano R.,Center for Oceanographic Research in the Eastern South Pacific
Chemistry and Ecology

Seasonal differences in the concentration and biochemical composition of seston have been assessed for the first time in the Humboldt Current System off northern Chile (21°S). The study comprised four seasonal surveys in the Bay of Chipana, including the summer and winter of 2006 and 2007, when El Niño 2006 and La Niña 2007 developed. Protein, lipid, carbohydrate and biogenic silica contents were measured in samples collected at four selected depths. The highest protein, lipid and carbohydrate concentrations were found at the fluorescence maximum (between 10 and 15 m depth), whereas the highest biogenic silica concentration was found 1 m above the seabed. When El Niño started developing, every variable showed low values throughout the water column; however, the lowest values were found when La Niña conditions dominated, together with low oxygen concentrations. Samples collected within the oxygen minimum zone (65 m depth) showed the lowest values for the water column and the lowest seasonal variations. After the evident decline coincident with El Niño 2006, the abundance and biochemical quality (high protein and lipid contents) of seston recovered earlier in the surface layer (upper 15 m) than at other depths. © 2012 Copyright Taylor and Francis Group, LLC. Source

Morales C.E.,Center for Oceanographic Research in the Eastern South Pacific | Morales C.E.,University of Concepcion | Loreto Torreblanca M.,Center for Oceanographic Research in the Eastern South Pacific | Hormazabal S.,UdeC | And 3 more authors.
Progress in Oceanography

In the Humboldt Current System, the region off central-southern Chile has relatively high eddy kinetic energy, generating an extensive coastal transition zone (∼600 km offshore) in which coastally derived eddies are recurrent features. This energy might promote strong exchanges of water, biogeochemical properties, and plankton between the coastal upwelling band and the adjacent oceanic zone. In this study, the mesoscale structure of epipelagic copepod assemblages and its relationship to environmental variability and the eddy field in the coastal transition zone and oceanic areas off Concepción (34-39°S, 73-84°W) were investigated. Zooplankton samples were collected during cruises of opportunity carried out during the 2006 coastal upwelling season and the oceanographic conditions were derived from satellite data on sea surface height, temperature, and chlorophyll a. The use of cluster analyses and indicator species revealed two main copepod assemblages: (i) species with a mainly coastal distribution, the maximum in total abundance being found nearshore and (ii) species with a mainly oceanic distribution (beyond ∼500 km from the coast), where a secondary maximum was observed. Both types of assemblages, however, included species widely distributed in the coastal transition zone. An ordination analysis identified sea surface temperature and chlorophyll a as the main factors affecting the distribution of most species and the clustering of stations resembled the distribution of these variables. Some of the large calanoid species that are common in shelf waters were more abundant within nearshore eddies rich in chlorophyll a and other cyclonic eddies far offshore; however, the eddy field alone did not explain the copepod mesoscale distribution. Altogether, the wide distribution of shelf/slope copepod species in this region suggests that physical and biological mechanisms might be acting to extend the productive area of the coastal upwelling zone. © 2009 Elsevier Ltd. All rights reserved. Source

Morales C.E.,University of Concepcion | Morales C.E.,Center for Oceanographic Research in the Eastern South Pacific | Hormazabal S.,Pontifical Catholic University of Valparaiso | Correa-Ramirez M.,UdeC | And 6 more authors.
Progress in Oceanography

Mesoscale features are recurrently found in the Coastal Transition Zone (CTZ) off central-southern Chile (~35-40°S), a region characterized by seasonal wind-driven coastal upwelling. In this study, oceanographic data from two consecutive cruises carried out during the upwelling season (January 2009) were combined with satellite time series data in order to characterize the structure and evolution of mesoscale eddies and to explore their influence on phytoplankton structure and nutrient distribution, in the context of organic carbon exchanges between the coastal upwelling zone and the CTZ. Two coastally-generated, contiguous mesoscale eddies (~2months old) were characterized: a surface cyclonic eddy (CC1) and a subsurface anticyclonic eddy (AA1). The distributions of salinity and dissolved oxygen, together with nutrients, suggested that both eddies were sites of vertical injection of high nutrient concentrations from the Equatorial Subsurface Water mass (ESSW) into the upper layer in the CTZ. In addition, eddy AA1, in combination with an upwelling plume, was involved in the offshore advection of nutrients from the core of the ESSW located in the coastal zone. At shallow depths (<50m), both eddies displayed moderate chlorophyll-a concentrations (up to 1mgm -3 in CC1 and 3mgm -3 in AA1) compared with the coastal maximum values (up to 18mgm -3). The photosynthetic communities within the eddies were mostly dominated by small cells (picoplankton in CC1 and nanoplankton in AA1) in contrast to microplankton dominance in the coastal band. These results support the view that relatively young mesoscale eddies, both the surface cyclonic and subsurface anticyclonic types, which originate in the coastal band of EBC regions, are important as sites of elevated nutrient concentrations which, in turn, can promote enhanced chlorophyll-a levels in the CTZ. © 2012 Elsevier Ltd. Source

Riquelme-Bugueno R.,University of Concepcion | Riquelme-Bugueno R.,Center for Oceanographic Research in the Eastern South Pacific | Escribano R.,University of Concepcion | Escribano R.,Center for Oceanographic Research in the Eastern South Pacific | Gomez-Gutierrez J.,National Polytechnic Institute of Mexico
Marine Ecology Progress Series

Seasonal and inter-annual variability in population abundance, biomass, and somatic and molt production of the Humboldt Current krill Euphausia mucronata were studied during a monthly time series (August 2002 to June 2007) at Stn 18 (36° 30' S, 73° 07' W) off central-southern Chile. Experimental measurements in krill were performed at Stn 18 (in 2007 and 2008) and northern Chile (2010) in order to estimate vital rates for use in E. mucronata secondary production calculation at Stn 18. Coastal upwelling intensity was the main oceanographic process found to control E. mucronata population abundance and biomass production on seasonal and inter-annual time scales. Spawning peaks and population structure indicate that E. mucronata produces at least 2 generations per year. The main spawning period occurs during the austral spring when phytoplankton concentration is high. A second, less intense spawning period occurs at the end of the austral summer and early autumn. E. mucronata had a mean biomass of 100 mg C m-3 and an integrated annual secondary production of 2432 mg C m-3 yr-1, with an overall production/biomass ratio (P/B) ratio of 24. In May 2007, a maximum daily integrated biomass of 5 g C m-3 and total daily secondary production of 63 mg C m-3 d-1 were observed. These estimates are considerably higher than those reported for other krill species in coastal upwelling regions. Multivariate analyses indicate that upwelling-favorable winds promote high E. mucronata biomass and secondary production, but higher abundance and biomass were found during the transition periods from upwelling to downwelling conditions. Results suggest that E. mucronata has a highly efficient behavioral strategy to attain high production rates and recover rapidly from potential offshore losses due to advective processes in a highly productive coastal upwelling ecosystem. Copyright © 2013 Inter-Research. Source

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