A SIGNATURE OF THE LOW FREQUENCY VARIABILITY ON THE BIOGEOCHEMICAL FEATURES OF THE NORTHERN HUMBOLTH UPWELLING ECOSYSTEM Graco Michelle1, Ledesma Jesús1, Purca Sara1, Dewitte Boris2, Castro Carmen3, Flores Georgina1Morón Octavio1and Dimitri Gutiérrez1 The Northern Humboldt Current Upwelling Ecosystem and particularly off Perú, isa “hot spot” for scientist around the world because of their unique characteristics and also paradigms, a high productivity and efficient trophic transfer, one of the intense and acidic Oxygen Minimum Zone (OMZ) and one of the nitrogen lost areas. All these features are under the impact of several temporal variability scales, as the strong interannual variability associated with the Equatorial remote forcing.In this context, we examined the oceanographic and biogeochemical variability off Central Perú, from a monthly time-series (1996–2009). We present evidences that the Equatorial Intraseasonal Kelvin waves appear to modulate the distribution of the OMZ in the area and in consequence affecting the chemical structure and biogeochemical activity in the system, not only at interannual but also intraseasonal time scale. These changes could have a deep impact in productivity,carbon and nitrogen loss. 1. Instituto del Mar del Perú (IMARPE), P.O. Box 22, Callao, Perú. Dirección de Investigaciones Oceanográficas. LMI DISCOH (WP3) IMARPE-IRD. 2. Laboratoired`Etudes en Géophysique et OcéanographieSpatiale (LEGOS), Toulouse, France 3. CSIC, Instituto de Investigaciones Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain.