Primary production and community respiration in the Humboldt Current System off Chile and associated oceanic areas

Abstract

The high biological productivity of the Humboldt Current System (HCS) off Chile supports an annual fish catch of over 7 million t. The area is also important biogeochemically, because the outgassing of recently upwelled water is modulated by contrasting degrees of biological activity. However, very few field measurements of primary production and planktonic respiration have been undertaken within the Eastern Boundary Current (EBC) system off Chile. In this study an estimate of primary production (PP) and surface planktonic community respiration is presented from several research cruises in the HCS and adjacent oceanic areas. The highest production levels were found near the coast correlating closely with known upwelling areas. Both gross primary production (GPP) and community respiration (CR) showed important spatial and temporal fluctuations. The highest water column integrated GPP was measured in the southern and central fishing area (19.9 g C m-2 d-1) and off the Antofagasta upwelling ecosystem (9.3 g C m-2 d-1). The range of GPP agrees well with values reported for Peru (0.05 to 11.7 g C m-2 d-1). The Coquimbo upwelling system, despite being an area of persistent upwelling, showed lower production and community respiration values than the Antofagasta and Concepcion Shelf areas. The lowest surface PP values were measured within the oceanic region adjacent to the northern coastal upwelling zones (0.8 ± 0.5 μg C l-1 h-1), though slightly enhanced biological production was found within the Nazca Ridge (1.5 ± 2.1 μg C l-1 h-1) that separates the Chilean and Peruvian deep basins.