Oceanic Budget of Dissolved Silicon

Abstract

THE oceanic budget of dissolved silicon has been discussed recently^1–3. Harriss¹ compared estimates of the rate of input of dissolved silicon by river drainage and the rate of its biological removal. He concluded that the reservoir of silicon in the ocean is being reduced. Gregor² and Calvert³ pointed out that Harriss estimated biological utilization of silicon and neglected resolution of skeletal remains, so that this conclusion is invalid. In their assessments the major terms of the budget equation are the rate of input of dissolved silicon by rivers and the rate of its biological removal to sediments. Their calculations rest essentially on Livingstone's compilation⁴ of data on river waters and the estimate made by Schutz and Turekian⁵, from the results of Lisitzin⁶, of the deposition of diatomaceous oozes in Antarctic waters. Antarctic deposition accounts for more than 80 per cent of Calvert's estimate of total biological removal (3.6 × 10¹⁴ g SiO₂/yr). Gregor's value for this term (6 × 10¹⁴ g SiO₂/yr) was apparently obtained by doubling the value for Antarctic deposition. Calvert's estimates for input by submarine weathering and vulcanism are negligible compared with the river input (4.3 × 10¹⁴ g SiO₂/yr). In Calvert's assessment the terms for input and biological removal are thus approximately equal. Gregor considers that the difference between his estimate of removal and the value for river input could be accounted for by submarine vulcanism.