Thermally tolerant corals have different mechanisms for responding to heat stress.
- Photo for illustration purposes only -
Published on Tuesday, August 17, 2021
Thermally tolerant corals have different mechanisms for responding to heat stress. This is the conclusion of a current study by an international team of researchers including the German Konstanz University biologist Professor Christian Voolstra.
The team examined responses to heat stress in the smooth cauliflower coral (Stylophora pistillata) in the Red Sea by combining the Coral Bleaching Automated Stress System (CBASS), a mobile rapid heat stress test, with molecular analyses, in order to identify different types of thermal tolerance.
The procedure is to be used worldwide, and the respective results could help provide corals with more targeted protection from the effects of climate change.
As a result of climate change, corals all over the world are currently dying. Within just a few decades, the global coral population has dropped by half, and, due to their locally adapted thermal tolerance, many corals are poorly prepared to respond to further increases in ocean temperatures. Some corals, however, are more adept at managing heat stress than others.
In order to elucidate the factors that contribute to higher thermal tolerance in corals, Voolstra and his colleagues introduced a new mobile testing system last year, the Coral Bleaching Automated Stress System (CBASS).
The system makes it possible to quickly identify corals that are particularly resilient. "This test procedure is a small revolution for me, because it allows researchers and conservationists alike to assess coral resilience anywhere on Earth and to find out how endangered each coral reef is, without the need for costly and sophisticated tech," Voolstra described the CBASS system in a previous article.
In the current study, the research team used the testing system to evaluate the thermal tolerance of the smooth cauliflower coral in different regions of the Red Sea. The results show that corals from the Gulf of Aqaba, the most northeastern arm of the Red Sea, demonstrate a remarkable thermal tolerance, up to about 7░C above the respective maximum monthly average for the warmest summer month, just like their peers from the central part of the Red Sea.
However, the absolute thermal tolerance of smooth cauliflower corals from the central part of the Red Sea is up to 3░C higher than for the same species in the Gulf of Aqaba, which could suggest that different tolerance mechanisms are at work.
In order to investigate this possibility, the research team conducted molecular analyses to elucidate mechanisms of thermal tolerance in corals from the different locations. Genetic examinations showed that smooth cauliflower corals from the Gulf of Aqaba respond to heat stress with a strongly altered gene expression, for example the increased production of certain proteins.
Parallel to this, the composition of the coral-associated bacterial communities changed. By comparison, corals from the central part of the Red Sea did not exhibit any of these changes when exposed to heat stress.
The molecular results support the idea that smooth cauliflower corals have different thermal tolerance mechanisms. "We interpret the response of the corals from the Gulf of Aqaba as that of a "resilient" population that directly and proportionally reacts to increases in temperature.
By contrast, the more static expression of genes of the corals from the central part of the Red Sea indicates a fixed reaction norm, irrespective of the heat stress applied, which provides "resistance" to high water temperatures, but at the cost of the ability to flexibly respond to further increases in temperatures," says Voolstra.
How should this research aid in addressing the issue of corals all over the world are currently dying? We would like to know your thoughts on this story. Send your comments to email@example.com
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