SEASONAL CHANGES IN PRIMARY PRODUCTION AND PHOTOADAPTATION
BY THE REEF-BUILDING CORAL ACROPORA GRANULOSA,
ON THE GREAT BARRIER REEF
B.E. CHALKER, T.COX and W.C.DUNLAP
Australian Institute of Marine Science, P.M.B.n03,
Townsville M.C., Queensland 4810, Australia
SUMMARY
Using previously developed equations, instantaneous rates of
~ situ photosynthesis were estimated for Acropora granulosa in
December and June at Davies Reef, Great Barrier Reef, Australia
(147°38'E, 18°51'S). Integration yielded estimated daily rates.
Diel p/R ratios are high from the surface to 35 m (5.8% of daily
surface light) and decline rapidly thereafter.
Diel p/R ratios are
greatest at a depth of 25 m (12% of daily surface light).
During
December the diel compensation depth is 60 m (1% of daily surface
light); during June, it is 45 m (1.6% of daily surface summer
light). Thus, it can be expected that Acropora granulosa will do
well metabolically from the surface to a depth transmitting 5.8% of
surface light; will do poorly from that depth down to a depth
·transmitting 1% of surface light; and is unlikely to survive at a,
depth below the 1% light level. These metabolic expectations
coincide with observed abundances from 6 to 51 m.
INTRODUCTION
Reef building corals contain large populations of the
endosymbiotic dinoflagellate Gymnodinium microadriaticum
(Freudenthal). The presence of the alga has profound physiological
consequences. A significant fraction of photosynthetically fixed