Cellular pathology and histopathology of hypo-salinity exposure on the coral Stylophora pistillata |
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Authors: | Craig A. Downs Esti Kramarsky-Winter Aaron Downs Yossi Loya |
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Affiliation: | a Pacific Biosciences Research Center, University of Hawaii at Manoa, 2500 Campus Rd., Hawaii Hall 211, Honolulu, HI 96822, USA b Haereticus Environmental Laboratory, P.O. Box 92, Clifford, VA 24533, USA c Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel d US National Oceanic and Atmospheric Administration, CCEHBR, Hollings Marine Laboratory, 331 Ft. Johnson Rd., Charleston, SC 29412, USA e Department of Molecular, Cellular and Developmental Biology, Yale University, 266 Whitney Ave., New Haven, CT 06511, USA f Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel |
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Abstract: | Coral reefs can experience extreme salinity changes, particularly hypo-salinity, as a result of storms, heavy rainy seasons (e.g., monsoons), and coastal runoff. Field and laboratory observations have documented that corals exposed to hypo-saline conditions can undergo extensive bleaching and mortality. There is controversy in the literature as to whether hypo-saline conditions induce a pathological response in corals, and if there is a relationship between decreasing salinity treatment and pathological responses. To test the hypothesis that hypo-salinity exposure does not have a pathological effect on coral, we used histological and cellular diagnostic methods to characterize the pathology in hypo-salinity-exposed corals. Colonies of Stylophora pistillata were exposed to five salinity concentrations [39 parts per thousand (ppt), 32 ppt, 28 ppt, 24 ppt, and 20 ppt] that may realistically occur on a reef. Histological examination indicated an increasing severity of pathomorphologies associated with decreasing salinity, including increased tissue swelling, degradation and loss of zooxanthellae, and tissue necrosis. Pulse-amplitude modulated chlorophyll fluorimetry kinetics demonstrated a decreasing photosynthetic efficiency with decreasing salinity conditions. Cytochrome P450 levels were affected by even slight changes in salinity concentration suggesting that detoxification pathways, as well as several endocrine pathways, may be adversely affected. Finally, these studies demonstrated that hypo-saline conditions can induce an oxidative-stress response in both the host and in its algal symbiont, and in so doing, may synergistically increase oxidative-stress burdens. As with other types of environmental stresses, exposure to hypo-saline conditions may have long-term consequences on coral physiology. |
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Keywords: | Cellular diagnostics Coral Hypo-salinity Oxidative stress |
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