Some Effects of Light on Coral Growth

Abstract

The rate of coral growth under varied light regimes was tested
\nusing 45Ca uptake while temperature was held constant. Pocillopora damicornis
\nand Acropora formosa, respectively, were used in Hawaii and Enewetak
\nunder natural and artificial light conditions. Light intensity and spectral
\ndistribution patterns were determined for all experiments.
\nPocillopora damicornis was tested under different natural light conditions
\nand total darkness. Light enhances calcification within limits. Calcification was
\nshown to have a negative regression with light at 380 nm when that light was
\npartitioned from visible light (400-800 nm), thus indicating longwave ultraviolet
\ninhibition.
\nAcropora formosa held for 6 hr of pretreatment under natural light conditions
\nduring the day or in the dark at night calcifies faster during the day
\nthan at night. This testing, which was conducted for 20 min under either dark
\nor light conditions, did not show a statistically significant difference between
\ndark or light testing conditions.
\nThis same species was pretreated for 4 hr with dark, low light, and high light
\nintensities at the same time of the day; then the samples were immediately
\ntested for calcification rate for 20 min under dark conditions. Those pretreated
\nunder high light calcified faster than those pretreated under low or dark
\nconditions, indicating a light-dependent lag effect.