Coral reefs around the world face a number of threats, the most pressing of which is rising water temperatures, which have risen by nearly one degree Celsius in many tropical regions over the past century.
Some corals are more resistant to heat stress than others as well microalgae that live in symbiosis with coral reefs, which provides them with energy.
In a study of hundreds of cedar coral colonies ( Montipora capitata ) In Kaneohe Bay, Hawaii, scientists at the University of Hawaii at Manoa examined two genera of algae, Cladocopium and Durusdinium, which typically form symbiotic relationships with Pacific reefs.
While Cladocopium is widespread, Durusdinium is generally found on corals in shallow waters exposed to higher levels of sunlight and sea surface temperatures, as well as in areas with higher temperature fluctuations. These latter algae are known to have a higher resistance to heat stress.
The scientists wanted to know if the algae had migrated into the reefs under heat stress, thus providing a degree of protection for the reefs.
“The corals in the far north and south of Kanoohe Bay were harboring fewer stress-resistant symbionts,” explains Mariana Rocha de Sousa, lead author of the study and a researcher at the university’s Institute of Marine Biology.
“This makes sense, because these areas experience less light, less heating and less temperature contrast. However, we were surprised to see that the symbiont actually responded to these subtle environmental differences in parts of the Gulf, something that has not been found in other studies.”
Algae grows and helps coral reefs
The new research provides encouraging insights into natural processes as temperatures continue to rise around Hawaii and across much of the Pacific Ocean where coral reefs live.
Rocha de Sousa says: “Our micro-sampling of coral colonies At a relatively small spatial gradient within Kaneohe Bay, the algal symbiont community structure can respond to the conditions in which the corals live.”
“This lays the foundation for understanding the role of environmental conditions in shaping how algal communities are distributed in space and time,” he adds. “Understanding the symbionts present in Hawaiian reefs and what drives symbiont community formation can help us predict how these corals will respond to heat stress in the future.”
In 2019, the corals in Kaneohe Bay underwent a massive bleaching process, and scientists are now investigating how corals of different species from different parts of the bay respond to heat stress.
Source/ merciful ecoportal.net/ barabic.com