The role of dissolved organic matter in the formation of polybromomethanes by marine algae

To estimate the amount of reactive dissolved organic matter (DOM) that produces polybromomethanes in coastal surface seawater, DOM was brominated by algal bromoperoxidase (BrPO) in the presence of H2O 2 and bromide. Bromoform (CHBr3) was the predominant species produced year-round in different waters. Production from nearshore seawater was greater than that from offshore seawater. The elevated CHBr3 production in the spring was associated with increased biological productivity and the resulting DOM. A large CHBr3 production potential (∼35 Gmol) was found in coastal waters independent of in vivo algal production. Terrestrially-derived DOM was responsible for dibromomethane (CH2Br2) production as its highest production was associated with the highest precipitation and presumably terrestrial runoff. Higher MW DOM fractions had more reactive DOM, as supported by higher CHBr3 production rate: [DOC] ratios. My results suggest that when cell-free/cell-attached BrPO is present in seawater, DOM could be brominated by BrPO-generated HOBr to produce CHBr3 and other volatile polybromomethanes.