Significance
Cadmium (Cd), a trace nutrient for marine algae, has a marine distribution that closely matches the macronutrients nitrate and phosphate. Sedimentary microfossil records of Cd provide reconstructions of past ocean nutrient distributions that facilitate understanding the role of the oceans in the carbon cycle and climate change. However, incomplete knowledge of processes that control the addition and removal of Cd in the ocean, and Cd’s variability relative to major nutrients, limit use of the paleoceanographic proxy. We present coupled data of Cd concentration and isotopic composition in seawater and suspended marine particles, indicating direct removal of Cd via coprecipitation with sulfide in oxygen-deficient waters. Thus, the marine Cd cycle may be highly sensitive to the extent of global oceanic oxygen depletion.