Significant attenuation on sinking Particulate Organic Carbon (POC) takes place within the upper hundreds meters of the water column. The study of the transfer efficiency is essential to improve our understanding of the ocean’s role in sequestering carbon. Here we present results on downward POC fluxes as well as export efficiency (i.e. export/production ratio) in the Southern Ocean, which is a key regulator of the global carbon cycle. We followed a vast algal bloom occurred around 51ºS 13ºW during three weeks in summer 2012 and used Th-234 as a particle tracer in combination with sediment traps (ST). The estimated POC fluxes at 100 m were high, averaging 19 ± 9 and 33 ± 10 mmol m-2 d-1 (ST and ST+Th-234, respectively), and they were reduced by a factor of 2 at 300 m in most of the stations. The export efficiency at 100 m was generally low (<10%), but it was >30% in some locations. Phytoplankton and sinking particles composition data will be also considered to better comprehend the dynamics affecting POC fluxes in the Southern Ocean.