Benthic in situ respiration in the upwelling area off central Chile

Abstract

Benthic O 2 uptake rates and O 2 microprofiles were measured in the upwelling area off central Chile. Measurements were performed both in situ and in the laboratory on recovered sediment cores. Comparison between the 2 data sets confirmed retrieval and handling artifacts inferred from previous studies. Onboard measurements indicated that the effects were mainly associated with core warming during recovery. Fauna mediated O 2 uptake was significant even at abyssal depths and generally in situ O 2 uptake rates were higher and showed stronger attenuation with water depth than previous measurements performed in the NE Pacific. However, O 2 uptake rates and O 2 penetration depths were very similar to measurements performed in the SE Atlantic, and the compiled data sets were approximated by simple exponential equations relating the measurements to water depth. By comparing our total O 2 in situ uptake rates to simultaneous measurements of primary production (PP) and new production (NP) of the overlying water column, it was calculated that the benthic mineralization accounted for 13 to 66 % of the PP and for 28 to 92 % of the NP at water depths shallower than 1000 m. At water depths from 1000 to 4000 m, the benthic mineralization equaled 2 to 11 % of the PP and 22 to 38 % of the NP. The benthic mineralization thereby accounted for a significant turnover of organic material even at the abyssal stations. The presented data add to the limited number of in situ deep sea mineralization measurements from the southern hemisphere.