This cruise dealt with measuring oxygen and nutrient fluxes at the water-sediment interface in the New Caledonian lagoon in summer. It followed an initial spatial monitoring survey done on a network of 11 stations along 2 coast-to-offshore transects sampled in winter (August 2001). The general objective was to study the consequences of human activities on a tropical ecosystem and more specifically matter exchanges between sediment and the water column. This research theme falls under the IRD's UR 103 and in the framework of the PNEC's New Caledonia study, both of which helped cofinance this cruise. The same network of stations was sampled and oxygen and nutrient fluxes determined by ex situ incubation of sediment cores and by oxygen profiles made using the micro-electrode method. More specific obejctives were to 1) confirmer the existence of spatial gradients in metabolic fluxes determined during the winter cruise, 2) compare winter and autumn situations in terms of benthic metabolism and 3) explain the differences obtained during the first cruise in oxygen flux results from ex-situ and in situ (benthic chambers) methods for stations located in the fine sand zone (reef barrier). This falls under the PNEC project, New Caledonia worksite.