Bridging the gap between functional genes and biogeochemistry: a DMSP case study
A large fraction of the surface ocean food web is active in producing and cycling both dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS). In addition to the potential climatic significance of DMS production, the role that these compounds play in mediating ecosystem dynamics remains unknown. An interdisciplinary dataset of biological, chemical and physical measurements was used to test current hypotheses of the role of light and carbon supply in regulating upper-ocean sulfur cycling in oligotrophic regions. Our results suggest that UV-A radiation dose plays an important role in both phytoplankton DMS production and bacterial DMSP degradation. We suggest a modified ‘bacterial switch’ hypothesis where the prevalence of different bacterial DMSP degradation pathways is regulated by a complex set of factors including carbon supply, temperature, and UV-A dose. Finally, numerical models of varying complexity were used to link genetic and enzyme data to biogeochemical rates.