Corals that are resistant to bleaching and those that were susceptible hosts two different communities of symbiotic algae. The distinguishing feature between these algal populations was found in their cells, in compounds known as lipids.
Researchers at Michigan State University and the University of Hawaii at Manoa have been uncovering clues as to why some corals bleach while others are resistant, information that could help reefs better weather warming waters in the future.
The team analysed the biochemistry of corals using mass spectrometers to understand what set resistant corals apart from susceptible ones. The scientists found that two different communities of algae lived within the corals. Inside the algae cells were compounds known as lipids.
Although the term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids. Lipids also include oils, waxes, certain vitamins (such as A, D, E and K), hormones and most of the cell membrane that is not made up of protein. Lipids are not soluble in water.
The researchers’ analysis detected two different lipid formulations. Bleaching-resistant corals featured algae that have what are known as saturated lipids. Susceptible corals had more unsaturated lipids.
"This is not unlike the difference between oil and margarine, the latter having more saturated fat, making it solid at room temperature," said MSU’s Robert Quinn, an assistant professor in the Department of Biochemistry and Molecular Biology
These findings indicate that natural bleaching susceptibility is manifested in the biochemistry of both the coral animal and its algal symbiont. This difference is stable through time and results in different physiological responses to temperature stress. Having these insights into the biochemical mechanisms of coral bleaching is promising for coral conservation and presents a valuable new tool for resilience-based reef restoration.