Evaluating the impact of upwelling and/or relaxation periods and of low dissolved oxygen regimes on the Concepcion shelf

A moderate oxygen minimum and nutrient-rich layer, associated with equatorial subsurface water (ESSW), are found at intermediate depths with the upper boundary in the upwelling season reaching to ~20m depth.

More or less lasting and intense suboxic and anoxic benthic conditions are created due to increased oxygen uptake linked to the seasonal higher input of organic matter and to the extended influence of hypoxic waters. Changes in the composition of ESSW can also result from local and remote physical forcing acting at different time- and space-scales. When oxygen supply falls or demand rises over the benthos, important changes can occur in the dominant metabolic pathways of microbial processes, in sediment and water chemistry, on the nutrient flux across the sediment-water interface, and in the structure and functioning of benthic communities.