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We hypothesized that seasonal and interannual climate-mediated changes in particulate organic carbon (POC) flux would affect bioturbation and ultimately the sequestration of organic carbon in the deep sea. An 18-yr timeseries photographic record from 4100-m depth in the northeast Pacific Ocean showed increased abundance of Echinocrepis rostrata, a common epibenthic echinoid and bioturbator, since the late 1990s. Abundance, size, and speed data were used to estimate bioturbation potential to track long-term changes in the volume of sediment disturbed by E. rostrata. There was no secular increase in E. rostrata bioturbation over 18 yr despite increased population size, although periodic variations in bioturbation were significantly correlated with POC flux. Expected changes in POC flux and bioturbation rates due to climate variation could lead to altered rates of carbon sequestration in deep-sea sediments, affecting the global carbon cycle. [ABSTRACT FROM AUTHOR]