The annual cycle of density of zooxanthellae in the tissues of field and laboratory-held Pocillopora damicornis (Linnaeus)

Three data sets collected over a number of years indicate that the density of zooxanthellae in the tissues of the hermatypic coral Pocillopora damicornis (Linnaeus) living in shallow water is approximately twice as high in winter as in summer. One of the data sets was obtained by sampling reef flat colonies. A second data set was obtained by sampling colonies maintained in outdoor laboratory tanks continuously supplied with sea water (laboratory controls) and a third set was maintained in similar tanks which were continuously supplied with ammonium enriched sea water. The set of nutrient-enriched corals showed higher algal densities than the control corals. Comparison of the annual pattern in these three sets with environmental variables suggests the pattern may be in response to seasonal differences in insolation, either Visible or UV. (C) 1997 Elsevier Science B.V.