This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Corals that partner with heat-tolerant algae may be better equipped to survive warming oceans—but that resilience comes with an unexpected trade-off, according to a new study from Boston University published in Science Advances. Corals depend on microscopic algae that live inside their tissues and provide nutrients through photosynthesis.
Some corals host the algal genus Durusdinium, which is known to help corals withstand higher temperatures and reduce the risk of bleaching during heat waves. The new study found that this heat tolerance comes at a cost. Corals hosting Durusdinium keep their stress response system in a heightened state.
That heightened response can help corals survive short-term heat stress, but when they encounter a second challenge—such as a bacterial infection—it can backfire, causing even greater tissue damage than in corals hosting less heat-tolerant algae. In other words, the tougher algal partner isn't free: It trades greater heat resistance for a higher risk when additional stressors strike. "Immune suppression is a well-known feature of many symbiotic relationships.
However, our study showed that when corals are associated with Durusdinium algae, their immune system is not suppressed," said lead author Jeric "JK" Da-Anoy, a recent Ph.D. graduate of the Davies Marine Population Genomics Lab. "When challenged by heat, these corals exhibit persistent upregulation of immune responses, resembling the chronic inflammation observed in other biological systems, including humans." The findings help explain why some corals that appear more resilient to warming oceans may still struggle to survive in increasingly complex and stressful environments. "As a researcher studying immunity, I find one of the most interesting findings of our study to be the identification of a potential mechanism that may help explain why some corals on the reef, particularly those hosting Durusdinium, are more prone to tissue loss and disease, while others are more resilient," Da-Anoy said.
"These findings also emphasize the important role that innate immunity plays in maintaining and regulating symbiosis." The research could help scientists develop reef restoration strategies that better account for the multiple environmental stresses corals face in a warming world. "As current oceans warm, there has been a lot of excitement about 'supercharging' corals with symbiotic heat-tolerant algae in order to help reefs survive the warming waters," said senior author Sarah W. Davies, associate professor of biology.
"However, our work shows that this strategy of inducing heat tolerance isn't free, and that the molecular processes that enable heat-tolerant algae to help corals avoid bleaching under short-term heat stress may make them more vulnerable when they encounter disease or other stressors. Understanding these trade-offs is critical if we want to design reef restoration strategies that will work in the real world, where corals rarely face just one stressor at a time." The study also provided hands-on research experience for undergraduate students in the BU Marine Program's Marine Semester. Working under the mentorship of Da-Anoy, four undergraduate students helped conduct the heat challenge experiments, caring for corals, monitoring water quality, collecting data and contributing to research that served as the building blocks for the published study.
Extract — continue reading at the source.
