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The responses of two species of hermatypic corals and their zooxanthellae to changes in light intensity
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|Title:||The responses of two species of hermatypic corals and their zooxanthellae to changes in light intensity|
|Authors:||Redalje, Randi C.|
|Issue Date:||Dec 1976|
|Publisher:||University of Hawaii at Manoa|
|Citation:||Redalje, Randi C. The responses of two species of hermatypic corals and their zooxanthellae to changes in light intensity. Honolulu (HI): University of Hawaii at Manoa, 1976.|
|Abstract:||The photosynthetic capabilities of zooxanthellae at various depths and light levels have been investigated by a number of workers (Barnes & Taylor, 1973; Wethey & Porter, 1976; Jeffrey & Haxo, 1968; Halldal, 1968). The relationship between photosynthesis and light has been described as a rectangular hyperbola. The Michaelis-Menton equation has often been fitted to the photosynthesis-light relationship for the coral-zooxanthellae complex as well as for phytoplankton (Wet hey & Porter, 1976; Caperon & Meyer, 1972; Steeman-Nielsen & Jorgensen, 1968). Wethey & Porter (1976) compared the photosynthetic rates of "sun" and "shade" corals. The terms "sun" and "shade" corals refer to corals collected from environments subjected to high and low light intensities respectively. Colonies of the foliaceous species, Pavona praetoria, collected from 10 meters, and 25 meters depth at Enewetak were compared. The maximum photosynthetic rate was higher for the 10 m. individuals than for the 25 m. corals. The "shade" corals, however (25 m.) were found to be light saturated at a lower light intensity than the shallow water colonies. This indicates that the "shade" corals are making efficient use of their photosynthetic machinery to obtain the maximum possible photosynthetic rate. Wethey and Porter (1976) suggest that the high photosynthetic rate of the "shade" corals at low light levels is due to their greater ability to absorb light in the 450 nm. light range. A large volume of phytoplankton research has investigated the differences between "sun" and "shade" adapted algae (algal cultures grown at high and low light intensities respectively) in their responses to changing light conditions (Steeman-Nielsen & Jorgensen, 1968; Steeman-Nielsen, 1973; Yentsch & Scagel, 1966; Ryther, 1956; Ryther & Menzel, 1959). These studies investigated the effects of changing light intensities on plant pigments, pigment ratios, enzyme systems, productivity, cell size, and growth rate, primarily on green algae, diatoms, and mixed phytoplankton populations. Although no studies of this type have investigated the light responses of dinoflagellates, it is assumed that the results obtained for diatoms apply to the Dinophyceae, which include zooxanthellae. The present study compares the effects of different light intensities on the zooxanthellae of "sun" and "shade" corals. Two Hawaiian species of hermatypic corals were selected for this purpose: Cyphastrea ocellina, a shallow reef species, and Leptoseris incrustans, a species limited to deep reef zones as well as shaded environments on shallow reefs.|
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|Appears in Collections:||M.S. - Zoology|
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