Humboldt (Southern) - Environment

At the seasonal scale, upwelling is the main process affecting the marine area off central Chile. For about half of the year (October–March), wind driven coastal upwelling fertilizes the surface waters promoting high primary production. During the rest of the year, winds are not favourable for upwelling and phytoplankton biomass and primary productivity are considerably diminished. At the interannual scale, the El Niño southern Oscillation is the main source of variability. However, the long-term decadal shifts in conditions in the whole Humboldt system seems to be the most important process in terms of the complete restructuring of the food web, from phytoplankton to top predators. The system is characterized by a superficial oxygen minimum zone (0.5 ml O2 L_1, 100–300m depth), which is associated with the Poleward Undercurrent and Equatorial Subsurface Waters. Topographic features such as embayments, capes, and submarine canyons generate several upwelling centres and coastal eddies.