Browsing by Author "Varas, M"

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    Distribution, population structure, population biomass and morphological characteristics of the tunicate Pyura stolonifera in the Bay of Antofagasta, Chile
    (2000) Castilla, JC; Guiñez, R; Alvarado, JL; Pacheco, C; Varas, M
    The present study analyzes the distribution, population structure, population biomass and morphological characteristics of the intertidal tunicate Pyura stolonifera (Heller, 1878) in the Bay of Antofagasta, Chile, where the species shows a reduced geographical range extending around 60-70 km. Three sites along its distribution were studied. At the central site the tunicate presents the widest intertidal belts, reaching nearly 11 m (the mid-intertidal-Pyura-zone shows the higher percent cover). Population dry biomass here averaged up to 20.45 kg.m(-2), representing one of the highest intertidal specific biomasses reported in the literature. Lower values occur towards the borders of its distribution. Population densities were over 1800 indiv..m(-2) at mid-intertidal-Pyura-belts. Crowding and competition potentially affect morphological characteristics and the energy/tissue allocation along the intertidal and geographical gradient of P. stolonifera.
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    Influence of coastal upwelling and El Nino-Southern Oscillation on nearshore water along Baja California and Chile
    (2004) Takesue, RK; van Geen, A; Carriquiry, JD; Ortiz, E; Godínez-Orta, L; Granados, I; Saldívar, M; Ortlieb, L; Escribano, R; Guzman, N; Castilla, JC; Varas, M; Salamanca, M; Figueroa, C
    [ 1] In order to determine the sensitivity of coastal upwelling tracers to seasonal wind forcing and El Nino-Southern Oscillation (ENSO) off Baja California and Chile, nearshore salinity, cadmium (Cd), and nutrients phosphate, silicate, nitrate+ nitrite were monitored in surf zone waters at six locations along the North and South American coasts during 1997-2000. The clearest responses to upwelling favorable wind forcing were observed at the southern tip of Baja California (23.3degreesN) and off central- southern Chile (36.5degreesS). Upwelling tracers at 23.3degrees N were also the most sensitive to El Nino: average summer Cd and nutrient enrichments were 60% lower following El Nino than during the previous non-El Nino upwelling season. At two sites on the northern and central Chile coasts, conditions associated with El Nino resulted in salinity anomalies >1. Such large shifts in nearshore water properties suggest it may be possible to reconstruct past ENSO patterns from geochemical paleonutrient/paleosalinity proxy records preserved in nearshore archives such as mollusc or foraminifera shells.