Silicon‐32 specific activities in coastal waters of the world oceans

Abstract

Measurements of 32Si specific activities in siliceous sponges collected from the coastal waters of the world oceans provide insight into the mixing processes of waters having radically different silicon concentrations. The measured specific activities of in sponges, which should correspond to the values of dissolved silicon (and 32Si) in the coastal waters of the oceans, lie in the range of 4–80 dpm of 32Si kg‒1 SiO2. They are inversely correlated with the concentrations of dissolved silicon in coastal waters from which the samples were collected, and specific activities in the sponges are lower than those measured in surface (0–150 m) ocean waters by direct sampling.In coastal regions there occurs a considerable influx of low specific activity continental waters and high specific activity intermediate and deep waters from the open ocean; the mixing between these various types of water, sampled by the sponge during its life time, determines the 32Si specific activity in sponges. Hence 32Si data in sponges should be useful for determining the budget of silicon in coastal regions.