Hallock,-P. The role of nutrient availability in bioerosion: Consequences to carbonate buildups. PALAEOGEOGR.,- PALAEOCLIMATOL.,-PALAEOECOL. 1988. vol. 63, no. 1-3, pp. 275-291. Zooxanthellate organisms, which are among the major carbonate producers on coral reefs, are highly adapted to nutrient- deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant. Reef- dwelling bioeroding organisms, on the other hand, seem to increase in abundance with increasing availability of nutrient and food resources. Maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion. The dynamic interplay between accretion and destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability. Some carbonate depositional hiatuses and bioerosional surfaces are local phenomena, evidence of responses to local increases in nutrient availability resulting from submergence of soils, runoff, or topographic upwelling. Other appear to reflect regional or worldwide events. Because many carbonate-producing organisms have life history strategies specialized to nutrient-deficient conditions, they are unable to compete when nutrients become plentiful. Events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea-surface nutrient availability worldwide. Such eutrophication could have caused widespread extinctions in reef communities.