| Affiliation: | (1) School of Ocean and Earth Science and Technology, Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1346, Kaneohe, HI 96744, USA;(2) Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822, USA;(3) University of South Florida, College of Marine Science, Institute for Marine Remote Sensing, St Petersburg, FL 33701, USA;(4) UR Coreus, Institut de Recherche pour le Développement, BP A5, 98848 Nouméa cedex, Nouvelle Caledonie |
| Abstract: | Spectral reflectance (R) of corals is a fundamental parameter to coral reef remote sensing. We explore general trends as well as geographic and taxonomic variabilities of coral R using a data set consisting of 5,199 R s measured in situ at depths of up to 15 m for 195 coral colonies at 11 sites worldwide. Coral R ranges in magnitude from ~0.5% at 400 nm to near 100% at 700 nm; mean coral R rises from ~2.5% at 400–500 nm to ~8% between 550 and 650 nm. All corals measured in this study exhibit one of two basic shapes of R, which we label the  brown and blue modes. We postulate that brown-mode R is determined by pigment absorption solely by zooxanthellae, while blue-mode R arises through expression of a non-fluorescing coral-host pigment. Taxonomic and geographic variabilities are approximately equal to global variability, both in magnitude and shape, indicating that coral R is independent of taxonomic or geographic differences. We reason that this is to be expected, since R is determined by pigments that are conservative across geographic and taxonomic boundaries. |
