Polyhalogenated Very Short Live Substances in the Atlantic Ocean, and their Linkages with Ocean Primary Production

The Halocarbon Air-Sea Transect - Atlantic (HalocAST-A) cruise was conducted aboard FS Polarstern during the ANT-XXVII/1 expedition. The ship departed from Bremerhaven, Germany on October 25^th and arrived in Cape Town, South Africa on November 24^th in 2010. The HalocAST-A cruise was devoted to studying air-sea fluxes of a suite of halocarbon compounds. Atmospheric mixing ratios and seawater concentrations of the halocarbons were continuously measured with the gas chromatograph - mass spectrometer (GC-MS). This study focuses on the polyhalogenated very short lived substances (VSLSs) such as bromoform (CHBr₃), dibromomethane (CH₂Br₂), chlorodibromomethane (CHClBr₂), and bromodichloromethane (CHBrCl₂). The goal of this study is to examine the distributions of these compounds and possible relationship between their emissions and oceanic primary production. Therefore, along with the halocarbon concentrations, parameters like dissolved organic carbon concentrations, nutrient concentrations, pigment concentrations, and picoplankton and heterotrophic bacteria counts were also determined. The observed saturation anomalies indicated these VSLSs were supersaturated for almost the entire duration of the cruise. The highest seawater concentrations for these compounds were observed near the Canary Islands. Air mixing ratios were also elevated in this region. The net fluxes for CHBr₃, CH₂Br₂, CHClBr₂, and CHBrCl₂ were 13.8 nmol m^-2 d^-1, 4.5 nmol m^-2 d^-1, 4.5 nmol m^-2 d^-1 and 1.2 nmol m^-2 d^-1, respectively. During the HalocAST-A cruise, these compounds exhibit similar trends with total chlorophyll a. Contributions from selected phytoplankton group will be further assessed through the use of individual pigment biomarkers.