MEPS 134:171-177 (1996)  -  doi:10.3354/meps134171

Action spectrum for the effects of UV radiation on photosynthesis in the hermatypic coral Pocillopora damicornis

Lesser MP, Lewis S

Colonies of the hermatypic coral Pocillopora damicornis were collected from the shallow reefs of Kaneohe Bay, Hawaii, to assess the wavelength-dependent effects of ultraviolet (UV) radiation on photosynthesis. Measurements of photosynthesis and respiration were made while corals were exposed to different UV irradiances, keeping visible radiation constant, using long-band pass filters. A differential action spectrum (biological weighting function) for the inhibition of photosynthesis by UV radiation was then determined for P. damicornis. The action spectrum revealed an increase in the wavelength-dependent effects of UV radiation on photosynthesis between 290 and 310 nm that is greater than those increases reported for action spectra on natural assemblages and unialgal cultures of marine microalgae. The greater effect at these wavelengths is a result of the high biologically effective doses of UV radiation experienced by these corals on shallow reefs, and the decrease in the absorbance of UV radiation by UV absorbing compounds found in the host tissues and algal symbionts between 290 and 310 nm. The irradiances of wavelengths in the region between 290 and 310 nm are those which will increase in the event of any decrease in stratospheric ozone over equatorial regions. If the observed sensitivity of P. damicornis in this spectral region is common in other species, it may have important consequences for growth, reproduction, and occurrence of the bleaching phenomenon for shallow water corals.

UV radiation . Corals . Action spectrum . Photosynthesis

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