Ruben Escribano

University of Concepción, Ciudad de Concepcion, Biobío, Chile

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Publications (67)113.84 Total impact

  • S. M. Cahuin, L. A. Cubillos, R. Escribano
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    ABSTRACT: Most of the studies investigating synchrony in fluctuations of abundance of small pelagic fish have been based on catch data only, which do not describe the dynamics of populations as a relative abundance index. In this paper, catch, biomass, recruitment and recruitment rate, were used to compare synchronous changes for two stocks of anchovy (Engraulis ringens) from 1982 to 2004. One is the North Central Peru stock (NCP) and the other is the shared South Peru-Northern Chile stock (SPNC). Correlation analysis demonstrated a significant association between population time series, particularly during the growing phase of the stocks. Thus, the synchronous fluctuation pattern of the two stocks is due to the recovery phase and probably driven by density-independent effects of simultaneous favorable environmental conditions occurring in the two regions. The conclusions were: (i) both NCP and SPNC anchovy stocks are in an overall positive phase of synchrony, (ii) higher correlations in the synchronous pattern of fluctuations occurred during simultaneous increase of biomass, and (iii) short-term fluctuations were negative when the abundance of the stock was lower and/or impacted by El Niño events.
    Journal of Applied Ichthyology 12/2014; · 0.90 Impact Factor
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    ABSTRACT: Estimating growth and production rates of mesozooplankton, and copepods in particular, is important in describing flows of material and energy though pelagic systems. Over the past 30 years, the Moult Rate (MR) method has been used to estimate juvenile copepod growth rates in �40 papers. Yet the MR method has been shown to have serious flaws. Here we re-examine the results from the majority of published MR method studies and re-estimate growth rates using the modified Moult Rate (MMR) method, which ascribes changes in mass to the appropriate time period over which it was accrued. The MR method has typically over-estimated growth rates (on 80% of occasions) for life stages where the subsequent stage is actively moulting; the median and mean MRvalues are 138 and 164%, respectively, of the corrected MMR values. We were unable to correct the original data for life stages that are followed by a nonmoulting stage, e.g. copepodite stage 5 to adult. We performed experiments with Calanus pacificus to estimate growth of stage C5 using an alternative method.We found that the error size and sign varied between mass type (i.e. DW, C and N). Recommendations for practical future assessments of growth in copepods are made.
    Journal of Plankton Research 06/2014; 36(5):1224-1232. · 2.44 Impact Factor
  • Katty Donoso, Ruben Escribano
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    ABSTRACT: A shallow oxygen minimum zone (OMZ) in the coastal upwelling zone off Chile may vertically confine most zooplankton to a narrow (< 50 m) upper layer. From laboratory experiments, we estimated oxygen consumption of the mesozooplankton community obtained in Bay of Mejillones, northern Chile (23°S) in May 2010, December 2010 and August 2011. Mass-specific respiration rates were in the range of 8.2–24.5 μmol O2 mg dry mass− 1 day− 1, at an average temperature of 12 °C. Estimates of the mesozooplankton biomass in the water column indicated that its aerobic respiration may remove daily a maximum of about 20% of oxygen available at the base of the oxycline. Since previous work indicates that zooplankton aggregate near the base of the oxycline, the impact of aerobic respiration on oxygen content might be even stronger at this depth. Mesozooplankton respiration, along with community respiration by microorganisms near the base of the oxycline and a strongly stratified condition (limiting vertical flux of O2), are suggested as being critical factors causing and maintaining a persistent subsurface oxygen-deficient ecological barrier (BEDOX) in the upwelling zone. This BEDOX layer can have a major role in affecting and regulating zooplankton distribution and their dynamics in the highly productive coastal upwelling zone of the Humboldt Current System.
    Journal of Marine Systems 01/2014; 129:166–177. · 2.48 Impact Factor
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    ABSTRACT: a b s t r a c t The recruitment rate of anchovy in the Peru–Chile upwelling system was studied by testing sensitive to environmental variability when the spawning stock is low in abundance. Times series of sea surface temperature, salinity, depth of the 15 1C isotherm, the upper limit of the oxygen minimum zone, upwelling indices, the Southern Oscillation Index, and indices El Niño 1þ2 and El Niño 3.4 were summarized trough Principal Component Analysis (PCA). The first PCA (PC-I) explained 57% of variance and was related to interannual variability driven by the El Niño-Southern Oscillation. The second Principal Component explained 15% of variance and was linked to upwelling indices. Anchovy recruitment rate anomalies were correlated with PC-I scores on the basis of a 6-year-moving-window and accumulated correlation as time progressed. Signifi-cant correlation coefficients were found when the spawning stock biomass was low in abundance before 1990. Once sufficient
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    Johanna Medellín-Mora, Rubén Escribano
    Latin American Journal of Aquatic Research 03/2013; 41(1):1-28. · 0.42 Impact Factor
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    ABSTRACT: 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-June 2007) at Station 18 (36º 30’ S; 73º 07’ W) off central-southern Chile. 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 two 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 2,432 mg C m-3 y-1, with an overall 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.
    Marine Ecology Progress Series 02/2013; 476:39-57. · 2.64 Impact Factor
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    Dataset: MBR VAR
    Victor M. Aguilera, Katty Donoso, Ruben Escribano
  • Victor M Aguilera, Ruben E Escribano
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    ABSTRACT: Seasonal cohorts of the large-sized copepod Calanoides patagoniensis allowed testing the relative ability of this species to exploit food resources that prevail during winter time in southern upwelling ecosystems of the Humboldt Current. This was achieved by considering a local winter flagellate assemblage (WFA), Thalassiosira rotula isolated from the local spring phytoplankton and a laboratory culture of Prorocentrum minimum, as food offers in consecutive 96 h experiments. Ingestion rates (IR) varied between 7 and 14 μg C f(-1) d(-1), egg production reached a peak of 70 eggs while egg production rates (EPR) varied between 27 ± 6 and 31 ± 4 eggs f(-1) d(-1). Feeding and reproductive traits were dependent on food offer, and after 72 h both IR and EPR decreased by 28% and 40% respectively, when copepods were steadily fed with the diatom. The relatively high reproductive performance supported by WFA was notable; showing the feeding behavior of this species can couple with food availability in the field with successful reproductive outcomes. Migration strategies allowing remain in upper food-rich coastal waters along with this flexible trophic behavior may better explain why this species is among the most recurrent ones in these variable yet productive upwelling areas.
    Marine environmental research 12/2012; · 2.34 Impact Factor
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    Sonia Yáñez, Pamela Hidalgo, Rubén Escribano
    Revista de biología marina y oceanografía. 08/2012; 47(2):295-310.
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    ABSTRACT: Two zooplankton time series from the coastal upwelling region off Chile were studied in terms of copepod biomass and abundance in relation with upwelling variation. The time series from Antofagasta (23°S) was collected between 1988 and 2008 and based on bi-annual sampling, whereas the time series from Concepción (36°S) was based on monthly samples between 2002 and 2008. In both sites, Ekman transport was derived from local wind obtained at coastal stations as an upwelling index. At both sites Ekman transport exhibited a seasonal patterns characterized by stronger upwelling during the spring-summer, although Ekman transport was stronger in northern Chile. Ekman transport also revealed three distinct periods of upwelling intensity between 1988 and 2008 in northern Chile. Copepod biomass varied in association with these periods, as follows: (1) 1988-1997 with a positive linear trend, (2) an abrupt decline in 1998-2000 after the 1997-1998 El Niño, and (3) a negative trend associated with increased upwelling from 2001 to 2008. A negative trend of zooplankton biomass and copepod abundance also occurred at Concepción during the period 2002-2008. Seasonal peaks in copepod biomass also coincided with the upwelling season (spring-summer). The correlation between variation in upwelling and copepod biomasses in northern Chile suggested that population dynamics of copepods may depend on intensity of upwelling. Although the underlying mechanisms are unclear, and several hypotheses dealing with bottom-up or top down factors can be put forth, our findings suggest that upwelling intensity operates through an optimal window for copepod abundance and biomass and increasing upwelling in the last decade (2000-2008) may has been unfavorable for copepod populations.
    Progress In Oceanography 05/2012; · 3.71 Impact Factor
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    ABSTRACT: Morphological changes in the exoskeleton of naupliar stages 2-6 and copepodid stages I-V of Rhincalanus nasutus are described. On the distal segment of naupliar antennule, one lateral seta and two medial setae are added during each molt to nauplius 3-6. A naupliar arthrite is a thick, distinctive structure on the coxa of antenna, and the exopod of this limb is patterned from the large proximal segment ofthat ramus. The coxal gnathobase of the mandible appears at nauplius 4. Buds of maxillule and maxilla are added during the molt to nauplius 5, and buds of maxilliped and swimming legs 1-2 are added during the molt to nauplius 6. The somite bearing maxilla clearly articulates completely with the somite bearing the maxilliped on the last two naupliar stages. This unusual articulation does not appear during copepodid development, and the somite bearing swimming leg 2 is the anterior articulating somite during this later phase. One articulating somite is added during molts to copepodid II-V. Segmentation of the antennule is completed by copepodid IV. Segmentation of the exopod of antenna does not change during the copepodid phase, but one segment is added to the endopod of maxilla. Segmentation and setation of the maxilliped follow the usual calanoid pattern. Buds of swimming legs 3-5 are ventrolateral on their somite. Their presumptive exopod has two attenuations; their presumptive endopod bears an attenuation and a seta. Segmentation of the rami of swimming legs 1-4 follows the common pattern for copepods except for the exopod and endopod of swimming leg 1 which are only 2-segmented. Cambios morfológicos en el exoesqueleto de estadios naupliares 2-6 y estadios copepoditos de Rhincalanus nasutus son descritos. El segmento distai de la anténula naupliar, muestra que una seta lateral y dos setas intermedias son adicionadas durante cada muda desde el nauplius 3 al nauplius 6. El attrito naupliar presenta una gruesa estnictura distintiva sobre la coxa de la antena y el exopodito està marcado desde el mayor segmento proximal de esta rama. La gnatobase de la coxa de la mandibula aparece en el nauplius 4. Inicios de la maxilula y maxilla aparecen durante la muda hacia el nauplius 5, e inicios del maxilipedo y los apéndices natatorios 1 y 2 aparecen durante la muda del nauplius 5 al nauplius 6. El somito presenta la maxila claramente y completamente articulada y el maxilipedo aparece en los dos Ultimos estadios naupliares. Esta inusuai articulación no aparece durante el desarrollo de copepoditos y el somito presenta la pata nadadora 2 en la articulación anterior en esta fase. Articulaciones del somito aparecen durante las mudas de copepodito II a copepodito V. La segmentación de la antenula es completada en el copepodito IV. La segmentación del exopodito de la antena no cambia durante la fase de copepodito, pero un segmento es adicionado en el endopodito de la maxila. La segmentación y setación de los maxilipedos sigue el normal patron de calanoideos. Los crecimientos de las patas natatorias 3-5 se encuentran en la parte ventral latéral de su somito respectivo. El incipiente exópodo posée dos atenuaciones; el incipiente endópodo exhibe una atenuación y una seta. La segmentación de la rama de las patas natatorias 1-4 siguen el patron comun para copépodos, excepto para el exopodito y endopodito de la pata natatoria 1, la cual està bi-segmentada solamente.
    Crustaceana 01/2012; 85(9):1025-1053. · 0.47 Impact Factor
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    ICES Journal of Marine Science 01/2012; 69:347-350. · 2.28 Impact Factor
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    ABSTRACT: This study assesses the spatial and temporal patterns of the euphausiid community from the coastal upwelling zone and oceanic areas of central-southern Chile, surveyed between August 2007 and November 2008. A total of 22 species were found, most of them already described for the region. The numerically dominant species was Euphausia mucronata for the entire study area (>60%), which was found in more oceanic waters (>90°W), thereby expanding its longitudinal distribution range. The species showed distinct spatial distribution patterns, allowing its classification as a coastal, oceanic, southern and northern species. The community descriptors – species richness, total abundance, Pielou and Shannon index – all had patterns associated with the cross-shelf and alongshore axes. Over a temporal scale, species abundance and community descriptors showed strong seasonal patterns. Abundances decreased offshore but diversity increased towards the oceanic area, revealing an inverse relationship between total abundance and the Shannon index. Diversity was positively related to sea surface temperature. Although the most abundant species were concentrated within the coastal zone, euphausiid abundance and diversity in the oceanic region were high. Our findings suggest that the high productivity of the upwelling region may sustain the euphausiid populations in the coastal transition zone and in the offshore region, and that high abundance and diversity across the entire region may be maintained by a highly heterogeneous environment promoted by upwelling, giving rise to an increased number of potential ecological niches.
    Progress In Oceanography 01/2012; 92-95:146–165. · 3.71 Impact Factor
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    ABSTRACT: Size spectra of the mesozooplankton community was studied under the influence of coastal upwelling during austral spring 2004 in the coastal upwelling zone off central-southern Chile. Size spectra were derived from the ZooImage analysis of digitalized zooplankton samples obtained from the upper 200 m during a survey carried out under active upwelling (November 2004). An upwelling filament extended up to 180 km offshore, and the upper boundary of the oxygen minimum zone (1 mL O2 L−1) varied between 20 m (nearshore) and 300 m depth (oceanic). The community descriptors (slope of the size spectra, size class index, abundance of size classes) were derived from the size spectra. Stepwise multiple regression analysis found significant correlations between these descriptors and oceanographic variables (temperature, dissolved oxygen, chlorophyll-a, OMZ depth). These data suggest an upwelling-dependent zooplankton distribution characterized by aggregations in a mid-shelf zone, where the log-normalized size spectra become flatter due to an increased abundance of larger size classes (>3 mm). In contrast, the inshore and offshore zones were dominated by small (<3 mm) size classes. The mid-shelf zone coincided with moderate levels of chlorophyll-a (ca. 1 μg L−1) and the OMZ depth near 200 m. These spatial patterns and slopes of the size spectra however, were subjected to a significant day vs. night effect mostly explained by the diel vertical migration of the euphausiid Euphausia mucronata. This migration can descend below 200 m during the daylight, causing the larger size classes to disappear from the size spectrum and resulting in a steeper slope. Time-dependent effects must, therefore, be considered when examining the spatial patterns of zooplankton in coastal upwelling zones.
    Progress In Oceanography 01/2012; 92-95:121–133. · 3.71 Impact Factor
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    ABSTRACT: a b s t r a c t This study assessed the structure of the copepod community in the upper 200 m of the coastal upwelling region off central-southern Chile in late summer 2009. Vertically stratified zooplankton samples and hydrographic variables were obtained from 42 stations over the continental shelf and oceanic areas. The survey took place during active upwelling, reflected by a cold upwelling plume extending out to 150 km offshore. A total of 62 copepod species were found. Of these, Oithona similis and Paracalanus indi-cus accounted for ca. 60% of the whole community. Species richness (R) and the Shannon–Wiener diver-sity index (H 0) were estimated, and the latter was additionally modified to incorporate the effect of copepod size on diversity (H 0 s). Samples were analyzed for two depth strata (0–50, 50–200 m) and for day vs. night conditions. Significant effects of day vs. night and strata on R, H 0 and H 0 s indicated that diel vertical migration between these two layers was an important source of variation in the zooplankton community. H 0 s seemed to represent copepod diversity better than R and H 0 over the spatial scale. H 0 s was also closely linked to colder upwelled water and the depth of the oxygen minimum zone following a principal component analysis. A positive relationship was even detected between depth of the oxygen minimum zone and H 0 s when strata and day/night effects were excluded. Our findings suggested that the coastal upwelling process could be an important driver of copepod diversity in this region. Upwelling leads to changes in the depth of the oxygen minimum zone and these changes impact the community composition due to species-dependent tolerances to low oxygen water.
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    Ruben Escribano, Carmen E. Morales
    Progress In Oceanography 01/2012; · 3.71 Impact Factor
  • Victor M. Aguilera, Katty Donoso, Ruben Escribano
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    ABSTRACT: Small-sized copepods represent a major contribution to the bulk of zooplankton biomass in highly productive coastal upwelling systems, and they are potentially the key link for channelling autotrophic C towards higher trophic levels, mainly via a heterotrophic food web. Here, we show how these small-sized copepods may efficiently exploit both autotrophic and heterotrophic components of the nanoplankton and microplankton size fractions throughout the year in the upwelling zone off Chile. The nutritional value of these food resources, in terms of C, N and lipid content, may vary extensively. However, copepods can successfully adjust their reproductive performance, measured as egg production and hatching success, in order to maintain high growth rates. This apparent flexibility enables copepod populations to sustain high production rates despite a strongly heterogeneous and variable food resource in the coastal upwelling zone. These findings provide further support to the hypothesis that those small-sized omnivorous copepods, not larger-sized, are the major organisms mediating the flux of phytoplankton C towards higher trophic levels in coastal upwelling systems.
    Marine Biology Research. 05/2011; 7:1-15.
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    ABSTRACT: 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.
    Chemistry and Ecology 01/2011; · 1.07 Impact Factor
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    ABSTRACT: The copepod community structure from the Northern and Central/southern upwelling regions off Chile was studied and compared. The derived community descriptors were species abundance (N), species richness (R) and the Shannon-Wiener diversity index (H′). These descriptors were related to distinct habitats and conditions, sea surface temperature (SST) and depth of the upper boundary of the oxygen minimum zone (OMZ). From 159 samples, obtained between 2002 and 2008, a total number of 118 species were found of which the calanoids Paracalanus indicus, Acartia tonsa and Eucalanus inermis, along with the cyclopoid Oithona similis, and the poecilostomatoids Triconia conifera and Oncaea media were the dominant species. H′ was higher in the northern region, but no differences in N and R were detected between regions. N was higher in the epipelagic vs the deep habitat, but R and H′ did not differ. N, R and H′ correlated positively to SST and negatively to OMZ depth. The ascent of the OMZ to the upper layer forced by upwelling was proposed as a mechanism that aggregates and increases copepod diversity in the food-rich photic zone. All these findings suggest a fundamental role of upwelling variation for modulating copepod dynamics and community structure in this highly productive but strongly variable marine ecosystem.
    Deep Sea Research Part II Topical Studies in Oceanography 12/2010; · 2.24 Impact Factor

Publication Stats

763 Citations
113.84 Total Impact Points

Institutions

  • 2002–2014
    • University of Concepción
      • Departamento de Oceanografía
      Ciudad de Concepcion, Biobío, Chile
  • 2008
    • Universidad Austral de Chile
      Ciudad de Valdivía, Los Ríos, Chile
  • 2004
    • Old Dominion University
      • Center for Coastal Physical Oceanography
      Norfolk, Virginia, United States
  • 1993–2002
    • University of Antofagasta
      • • Instituto de Investigaciones Oceanológicas
      • • Facultad de Recursos del Mar
      Antofagasta, Region de Antofagasta, Chile