the humboldt current system of northern and central chile - figema

THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILEVargas & González 2004) and gelatinous food web (H.E. González et al. 2004b). These trophicflows are important throughout the whole year in oceanic areas and are highly relevant during thenon-productive periods (including EN events) in coastal upwelling areas.The carbon budget of the photosynthetically generated OM in the coastal areas of the HCS hasbeen under debate for many years (Bernal et al. 1989, González et al. 1998). It is accepted nowadaysthat the fraction of the PP removed from the photic zone, which is highly variable on an annualbasis (Hebbeln et al. 2000a), strongly depends on the various biological (internal metabolism),physical (stratification/mixing), and chemical (nutrient rich/poor waters) processes involved as wellas the time of year. However, the sources of this variability, both in space and time, have beenpoorly analysed until recently (Morales & Lange 2004), mainly because of the lack of long-termtime-series studies. In Figure 4 the main pathways of the photosynthetically generated organiccarbon are depicted. Very high bacterial secondary production (BSP) has been reported in thecoastal area of northern-central Chile (Troncoso et al. 2003, Cuevas et al. 2004), suggesting a tightcoupling between PP and BSP. The pivotal role of bacteria is supported by the exceptionally highPrimary productionMicroplanktonrespiration15135700Zooplanktongrazing455Bacterial secondaryproduction1106Iquique −20°AntofagastaExportproduction114A Coastal area off AntofagastaPrimary productionCoquimbo−25°−30°Southern latitudeMicroplanktonrespiration4570Zooplanktongrazing321−35°1400Bacterial secondaryproductionConcepción2300−40°Exportproduction336B Coastal area off ConcepciónFigure 4 Photosynthetically generated carbon and its flows (rate estimates in mgC m –2 d –1 ) through the morerelevant biological processes in the upwelling system off Antofagasta (23°S) and Concepción (37°S).211