Spatial and Temporal Distributions of Polybrominated Very Short Live Substances in the Atlantic Ocean, and Their Linkages with Ocean Primary Production

Bromoform (CHBr₃), dibromomethane (CH₂Br₂) and other very short-lived substances (VSLS) were measured during 5 cruises in the Atlantic Ocean from 1998 to 2010. These cruises were conducted over large meridional (62° N - 60° S) and zonal (11° W – 86° W) ranges in the Atlantic Ocean. Elevated atmospheric mixing ratios and seawater concentrations of CHBr₃ were observed coincident with regions of elevated chlorophyll a, such as the equatorial region, upwelling zones and coastally influenced shelf waters, suggesting that processes related to ocean primary production may have contributed to CHBr₃ production. While CH₂Br₂ seawater concentrations exhibit similar trends with CHBr₃, it is more well-mixed in the atmosphere, due to its longer atmospheric lifetime. The sea-to-air flux maxima for CHBr₃ and CH₂Br₂ were observed in coastally influenced shelf waters. Assuming the fluxes measured in the Atlantic open ocean are globally representative, the extrapolated CHBr₃ global open ocean annual net sea-to air flux is 0.13 - 3.6 Gmol Br yr^-1. Biological parameters including pigment biomarkers and flow cytometeric picoplankton counts were measured during one of the cruises conducted in 2010 (HalocAST – A). None of the pigment biomarkers yield significant correlations with CHBr₃ and CH₂Br₂. While zeaxanthin does not distinguish between Synechococcus and Prochlorococcus, flow cytometeric cell counts do allow for their separation and determination of their individual abundances, as well as providing cell abundance information for other picoeukaryotes and heterotrophic bacteria. Seawater concentrations of CHBr₃ were significantly correlated with Synechococcus near the Northwestern African upwelling zone but not anywhere else during the HalocAST – A cruise. These findings suggest that more specific parameters are needed for assessing biogenic sources of the VSLS during large oceanographic transects due to changing biomes during the course of the cruise. A new solubility relationship to temperature and salinity determined from recent laboratory studies will be presented along with an updated VSLS net sea-to-air net flux.