Production of Calcium Carbonate on the Mainland Shelf of Southern California1

Although calcareous organisms are abundant on hard‐bottom portions of the southern California mainland shelf, negligible amounts of CaCO 3 are accumulating there. Data collected at three localities and 22 stations along the southern California coastline give subtidal rates of CaCO 3 production by calcareous organisms, from turnover rates calculated from growth rate data, from mortality calculations based on size distribution and growth data, and from miscellaneous information, near 400 g CaCO 3 m ‒2 yr ‒1 . Although this temperate climate production rate is lower than rates of coral reef production, it is similar to tropical nonreef production rates and much higher than pelagic production rates of CaCO 3 . The CaCO 3 produced is lost from the mainland shelf, probably by transportation to adjacent basins, and then is apparently in large part dissolved. About 4 × 10 10 g CaCO 3 yr ‒1 are produced across 10 3 km 2 of the shallow hard‐bottom shelf areas of southern California and subsequently removed from those areas.