Mechanisms driving the fate of the organic matter in deep sea waters: quality and quantity of the substrates

Abstract

Three different incubation experiments of 25 days long were conducted during the last FICARAM cruise in 2013. Water was sampled along the Southern Atlantic Ocean from more than 3000 m depth. Four experimental conditions were set for each experiment: K was kept as a control, CL received additions of labile compounds (acetate and glucose), CM got a mixture of twenty organic compounds and CR received a mixture of humic acids as examples of recalcitrant compounds. After 10 days of incubation bacteria population reached the stationary phase. Changes in composition and quality of DOM were tracked by calculating the absorption coefficient a254. While the release of humic like compounds was not remarkable in CR and K conditions, for CM and CL the concentration of aromatic substances increased associated to bacterial growth. Protein-like compounds were generated as a by-product of bacterial metabolism in conditions were the source of C was a mixture of acetate and glucose. Also a 5-components PARAFAC model was validated for the entire transect in order to track the compounds present in our water incubations