Dissolution and behavior of particulate biogenic matter in the ocean: Some theoretical considerations

For calcareous and siliceous biogenic particles in the micron size range, the Stokes' settling velocities are sufficiently small such that appreciable dissolution may be expected in transit through a vertical column of ocean water. In the course of settling the rate of addition of dissolved biogenic carbon and silicon to seawater at all depths is nearly constant provided the macroscopic rate of dissolution is a phenomenon dependent on the surface area and invariant with depth. Settling and dissolution of particles in the presence of upwelling water result in the formation of layers of high particle concentrations. Possible coagulation of the submicron-size particles in such layers does not lead to a significant reduction of the particle concentrations. Upper-limit estimates of the rates of addition to ocean water (depths of 1–4 km), owing to dissolution of settling particles, are: carbon, (3–60) × 10−9 g cm−3 yr−1, and silicon, 4 × 10−7 g cm−3 yr−1.