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

The high biological productivity of the Humboldt Current System (HCS) off C hile supports an annual fish catch of over 7 million t. The area is also im portant 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 hav e been undertaken within the Eastern Boundary Current (EBC) system off Chil e. In this study an estimate of primary production (PP) and surface plankto nic community respiration is presented from several research cruises in the HCS and adjacent oceanic areas. The highest production levels were found n ear the coast correlating closely with known upwelling areas. Both gross pr imary production (GPP) and community respiration(CR) showed important spati al and temporal fluctuations. The highest water column integrated GPP was m easured 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 o f 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 upw elling, showed lower production and community respiration values than the A ntofagasta and Concepcion Shelf areas. The lowest surface IPP values were m easured within the oceanic region adjacent to the northern coastal upwellin g zones (0.8 +/- 0.5 mu g C 1(-1) h(-1)), though slightly enhanced biologic al production was found within the Nazca Ridge (1.5 +/- 2.1 mu g C 1(-1) h( -1)) that separates the Chilean and Peruvian deep basins.