期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：14
页码：8007-8012
DOI：10.1073/pnas.96.14.8007
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Coral bleaching has been defined as a general phenomenon, whereby reef corals turn visibly pale because of the loss of their symbiotic dinoflagellates and/or algal pigments during periods of exposure to elevated seawater temperatures. During the summer of 1997, seawater temperatures in the Florida Keys remained at or above 30{degrees}C for more than 6 weeks, and extensive coral bleaching was observed. Bleached colonies of the dominant Caribbean reef-building species, Montastrea faveolata and Montastrea franksi, were sampled over a depth gradient from 1 to 17 m during this period of elevated temperature and contained lower densities of symbiotic dinoflagellates in deeper corals than seen in previous "nonbleaching" years. Fluorescence analysis by pulse-amplitude modulation fluorometry revealed severe damage to photosystem II (PSII) in remaining symbionts within the corals, with greater damage indicated at deeper depths. Dinoflagellates with the greatest loss in PSII activity also showed a significant decline in the D1 reaction center protein of PSII, as measured by immunoblot analysis. Laboratory experiments on the temperature-sensitive species Montastrea annularis, as well as temperature-sensitive and temperature-tolerant cultured symbiotic dinoflagellates, confirmed the temperature-dependent loss of PSII activity and concomitant decrease in D1 reaction center protein seen in symbionts collected from corals naturally bleached on the reef. In addition, variation in PSII repair was detected, indicating that perturbation of PSII protein turnover rates during photoinhibition at elevated temperatures underlies the physiological collapse of symbionts in corals susceptible to heat-induced bleaching.
