Seminal Early Studies on the Mechanisms of Coral Bleaching.

Abstract

In their article “Temperature Stress Causes Host Cell Detachment in Symbiotic Cnidarians: Implications for Coral Bleaching” in the June 1992 issue of The Biological Bulletin, Ruth Gates, Garen Baghdasarian, and Len Muscatine launched a new discipline within coral biology aimed at discovering the cellular mechanisms underlying temperatureinduced coral bleaching. At the time, the phenomenon of coral bleaching, the paling of coral tissues due to loss of their endosymbiotic dinoflagellate algae (once called zooxanthellae but now known to be members of the diverse family Symbiodiniaceae), was just beginning to be observed and documented in nature and linked to high-temperature anomalies (Glynn, 1990. Elsevier Oceanogr. Ser. 1990: 55–126). Now, 30 years later, we are witnessing the collapse of the world’s coral reefs as climate change drives high-temperature events that cause vast stretches of reef to bleach and ultimately die, resulting in the destruction of the entire ecosystem (vanWoesik et al., 2022.Glob. Change Biol., https://doi.org/10.1111/gcb.16192). Coral biologists the world over are racing to develop solutions to help coral reefs survive in the Anthropocene (National Academies of Sciences, Engineering, and Medicine, 2019. A Research Review of Interventions to Increase the Persistence and Resilience of Coral Reefs). Many of their approaches are based on foundational knowledge of the mechanisms driving coral bleaching (a form of dysbiosis), the area that this seminal paper helped to start. In the study, Gates and colleagues aimed to document the process of symbiont release from hosts at the cellular level. They started by setting up a variety of possibilities for mechanisms of bleaching, in Figure 1. This now-iconic figure (Fig. 1) has been reproduced, modified, and added to innumerable times in both original papers and reviews (e.g., Weis, 2008. J. Exp. Biol. 211: 3059–3066; Bieri et al., 2016.