Growth Rates of Phosphate Nodules from the Continental Margin Off Peru

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Science  26 Mar 1982:
Vol. 215, Issue 4540, pp. 1616-1618
DOI: 10.1126/science.215.4540.1616


Modern sea-floor phosphorite nodules sampled from off the coast of Peru are shown to grow at rates of millimeters per thousand years in spite of the fact that the measured accumulation rates of the underlying sediment are two to four orders of magnitude faster. Phosphate nodules grow downward into soft sediment, and the rates of phosphorus accumulation into nodules are approximately equal to the upward diffusive flux of dissolved phosphate inferred from pore water profiles. These results demonstrate that phosphorus in nodules originates from regeneration in sediments rather than as a result of direct precipitation from bottom waters.