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Spatial and temporal distributions of bromoform and dibromomethane in the Atlantic Ocean and their relationship with photosynthetic biomass
Author(s) -
Liu Yina,
YvonLewis Shari A.,
Thornton Daniel C. O.,
Butler James H.,
Bianchi Thomas S.,
Campbell Lisa,
Hu Lei,
Smith Richard W.
Publication year - 2013
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/jgrc.20299
Subject(s) - biogeochemical cycle , seawater , bromoform , oceanography , trace gas , phytoplankton , chlorophyll a , pelagic zone , upwelling , biomass (ecology) , environmental science , chemistry , environmental chemistry , atmospheric sciences , nutrient , geology , biochemistry , organic chemistry , chromatography , chloroform
Atmospheric mixing ratios and seawater concentrations of bromoform (CHBr 3 ), dibromomethane (CH 2 Br 2 ), and other brominated very short‐lived substances (BrVSLS) were measured during five cruises from 1994 to 2010. These cruises were conducted over large latitudinal (62°N–60°S) and longitudinal transects (11°W–86°W) in the Atlantic Ocean. Elevated seawater concentrations of CHBr 3 and CH 2 Br 2 were often observed in regions where chlorophyll a concentrations were also elevated, which suggests biogeochemical processes associated with photosynthetic biomass may be related to CHBr 3 and CH 2 Br 2 production. Our results suggest that, at least in the open ocean, several phytoplankton taxa may contribute to the production of these trace gases. While observed correlations between CHBr 3 and CH 2 Br 2 in different regions are usually interpreted as common sources for these compounds, results in this study suggest different biogeochemical processes may contribute separately to the production of these trace gases. Heterotrophic bacterial abundance was significantly correlated with CH 2 Br 2 , but not with CHBr 3 , which suggests the biogeochemical processes associated with heterotrophic bacteria may be related to CH 2 Br 2 in seawater but probably not to CHBr 3 . In general, the Atlantic Ocean is a net source for CHBr 3 and CH 2 Br 2 , except for a few locations where these trace gases were undersaturated in seawater. Assuming fluxes measured in the Atlantic open ocean are globally representative, the resulting extrapolated, global open‐ocean annual net sea‐to‐air fluxes calculated from data from the five cruises was estimated at 0.24–3.80 Gmol Br yr −1 for CHBr 3 and 0.11–0.77 Gmol Br yr −1 for CH 2 Br 2 .