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 ³²Si 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.