Of the life processes on a coral reef, calcification produces the most conspicuous end product--the reef framework and sediments. Most of the information relevant to coral-reef calcification comes from studies of the rates of CaCO₃ retention by the reef or studies of individual organism calcification rates. Neither of these types of studies really assesses the rate at which the reef community produces CaCO₃.

Alkalinity depletion as water flows across a reef, together with volume transport of that water, can be used to compute the rate of reef calcification. This procedure has been employed across a predominantly coral community and across a predominantly coralline algal community on windward inter-island reef flats of Eniwetok Atoll, Marshall Islands.

The mean alkalinity of water approaching the reef is about 2.30 meq/l, and the alkalinity as the water crosses the reef is typically depleted by less than 0.01 meq/l. The product of ^Dgr alkalinity times volume transport, divided by the reef length, averages approximately 0.0025 (meq/sq m)/sec, with no significant difference in depletion rate between the 2 calcifying communities examined. This alkalinity depletion rate is equivalent to a CaCO₃ production rate of 4 × 10³ (g CaCO₃/m²)/year.

If the porosity of the sediment produced by calcification is 50%, then the CaCO₃ production rate is sufficient for an upward reef growth rate of about 3 mm/year. Because the present rate of eustatic sea level rise is considerably less than 3 mm/year, the reef is either catching up with sea level, or most of the CaCO₃ produced is being removed. Sediment accumulations downstream from actively calcifying reef areas favor the latter hypothesis.

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