In situ oxygen tracers (triple oxygen isotope and oxygen/argon ratios) were used to evaluate meridional trends in surface biological production and export efficiency across~8000 km of the tropical and subtropical South Atlantic in March-May 2013. We used observations of picophytoplankton, nanophytoplankton, and microphytoplankton to evaluate community structure and diversity and assessed the relationships of these characteristics with production, export efficiency, and particulate organic carbon (POC) fluxes. Rates of productivity were relatively uniform along most of the transect with net community production (NCP) between 0 and 10 mmol O 2 m À2 d
À1, gross primary production (GPP) between 40 and 100 mmol O 2 m À2 d À1 , and NCP/GPP, a measure of export efficiency, ranging from 0.1 to 0.2 (0.05-0.1 in carbon units). However, notable exceptions to this basin-scale homogeneity included two locations with highly enhanced NCP and export efficiency compared to surrounding regions. Export of POC and particulate nitrogen, derived from sediment traps, correlated with GPP across the transect, over which the surface community was dominated numerically by picophytoplankton. NCP, however, did not correlate with POC flux; the mean difference between NCP and POC flux was similar to published estimates of dissolved organic carbon export from the surface ocean. The interrelated rates of production presented in this work contribute to the understanding, building on the framework of better-studied ocean basins, of how carbon is biologically transported between the atmosphere and the deep ocean.Plain Language Summary Photosynthesis in the ocean results in the drawdown of atmospheric carbon dioxide. In this study, we use biological and chemical data from a cruise transiting 8000 km of the South Atlantic Ocean in order to study how biological communities in the surface ocean produced oxygen and took up carbon dioxide from the atmosphere in order to grow and how that carbon was consumed or transferred to greater depths away from the atmosphere. Specifically, we used dissolved gases to measure phytoplankton respiration and photosynthesis and sediment traps to collect falling particles; we also determined phytoplankton community structure at 5 m of water depth. This combination of information about the biological community, production, and export across a large region provides insights into the relationships underlying carbon cycling in the South Atlantic.