Acá hay un par de estudios interesantes para aquellos que gusten de estudiar mas a fondo el tema de iluminación en los corales..........
Photo-acclimation dynamics of the coral Stylophora pistillata to low and extremely low light
E. A. Titlyanova, b, , , , T. V. Titlyanovaa, K. Yamazatoc and R. van Woesikd
a Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, Vladivostok 690041, Russia
b Sesoko Marine Science Center, University of the Ryukyus, 3422 Sesoko, Motobu-cho, Okinawa 905-205, Japan
c Research Institute for Subtropics, 1 Asahimachi, Naha, Okinawa 9003-0029, Japan
d Department of Marine Sciences, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan
Received 22 February 2001; revised 28 April 2001; accepted 10 June 2001.
Abstract
Photo-acclimation dynamics of the symbiotic coral Stylophora pistillata to lowering light intensities in the range of 95% to 0.8% of incident surface photosynthetic active radiation (PAR0) was studied. Coral colonies were sampled from 1- to 2-m depths in open and shaded habitats from the fringing reef of Sesoko Island (near the Tropical Biosphere Research Center, University of the Ryukyus) Okinawa, Japan. Photo-acclimation of exterior branches of coral colonies were examined in outdoor aquarium, where light regime and feeding were similar to field conditions. Two photo-acclimation reactions were studied: (1) changes in chlorophyll concentrations in zooxanthellae; (2) changes in zooxanthellar population density in coral branches. In parallel, we measured an average volume of zooxanthellae, proliferating zooxanthellae frequency (PZF) and degrading zooxanthellae frequency (DZF). It was shown that the coral S. pistillata can survive and acclimate to a wide range of light intensities from 95% to 0.8% PAR0. Acclimation to low light (30% and 8% PAR0) involves maximizing the light harvesting capacity by increasing photosynthetic pigment concentration in zooxanthellae and zooxanthellar population density in coral branches. Under extremely low light (0.8% PAR0), the coral lost zooxanthellae by degradation (perhaps digestion) and retained zooxanthellae-accumulated high concentrations of chlorophyll. The photo-acclimation process is dynamic and immediate. Changes in pigment concentrations in zooxanthellae occurred within 2–4 days and changes in zooxanthellar population densities occurred within 40 days. Zooxanthellae population densities were regulated by changes in rates of division and degradation of symbiotic cells.
Otro estudio interesante, cuyo texto completo se puede encontrar
acá.
Exp Biol. 2003 Nov;206(Pt 22):4041-9.
Photobehavior of stony corals: responses to light spectra and intensity.
Levy O, Dubinsky Z, Achituv Y.
Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel.
Tentacle expansion and contraction were investigated in four zooxanthellate coral species and one azooxanthellate coral (Cladopsammia gracilis). Favia favus, Plerogyra sinuosa and Cladopsammia gracilis expand their tentacles at night, while tentacles in Goniopora lobata and Stylophora pistillata are expanded continuously. Light at wavelengths in the range 400-520 nm was most effective in eliciting full tentacle contraction in F. favus and in P. sinuosa. Higher light intensities in the range 660-700 nm also caused tentacle contractions in F. favus. Tentacles in C. gracilis did not respond to light. Zooxanthellar densities in tentacles were significantly higher in G. lobata, which has continuously expanded tentacles, than in F. favus and P. sinousa, where tentacles are expanded at night. Photosynthetic efficiency in F. favus and P. sinuosa was lower in specimens with contracted tentacles. However, in the dark, no differences were found in the maximum quantum yield of photochemistry in PSII (Fv/Fm) of the expanded versus the contracted tentacles of any of the four species. This work suggests that species whose tentacles remain continuously expanded have either dense algal populations in their tentacles, as in G. lobata, or minute tentacles, like S. pistillata. Dense algal populations in tentacles allow harvesting of light while small tentacles do not scatter light or shade zooxanthellae in the underlying body of the polyp
Este último estudio es muy bueno y recomiendo leerlo completo si es que pueden....
), que evolutivamente son posteriores a las cianos y a las diatomeas, y en cualquier caso "solo" unos pocos millones de años antes que los corales.
