Dissolved organic matter (DOM) remineralization is limited to a greater or lesser degree at different layers in the ocean. In order to investigate the key abiotic and biotic factors that may enhance DOC remineralization in the deep ocean, we studied the changes in function and structure of deep prokaryotic communities after additions of the same amount of dissolved organic compounds with different quality. We performed experiments with deep sea prokaryotic assemblages subjected to four different treatments: CL (addition of labile DOC), CM (addition of a mix of organic compounds with different lability) and CR (addition of recalcitrant humic acids) and K (control). Prokaryotic biomass markedly increased when the labile compounds or the diverse chemical mixture were added (CL and CM treatments), whereas the prokaryotic response was lower under either the control K or CR treatments. Accordingly, we found lower activity and similar patterns of extracellular enzymatic activities in CR and K compared to CL and CM treatments. In all treatments a decrease in prokaryotic richness consistently occurred along the incubations, but interestingly, the decrease was lower in the control and in the CR treatments. Our results indicate that the chemical diversity of organic matter is a key factor determining microbial structure and activity in the deep ocean

ASLO Aquatic Sciences Meeting, Resilience and Recovery in Aquatic Systems, 4-9 June 2023, Palma de Mallorca, Spain

Peer reviewed