Following the Deepwater Horizon oil spill of 2010, large amounts of biodegraded oil (petrocarbon) sank to the seafloor. Our objectives were to 1) determine post-spill isotopic values as the sediments approached a new baseline and 2) track the recovery of affected sediments. Sediment organic carbon Delta C-13 and Delta C-14 reached a post spill baseline averaging -21.2 +/- 0.9 parts per thousand (n = 129) and-220 +/- 66 parts per thousand (n = 95). Spatial variations in seafloor organic carbon baseline isotopic values, C-13 and C-14, were influenced by river discharge and hydrocarbon seepage, respectively. Inverse Distance Weighting of surface sediment Delta C-14 values away from seep sites showed a 50% decrease in the total mass of petrocarbon, from 2010 to 2014. We estimated a rate of loss of -2 x 10(9) g of petrocarbon-C/year, 2-11% of the degradation rates in surface slicks. Despite the observed recovery in sediments, lingering residual material in the surface sediments was evident seven years following the blowout.