Modified microalgae help protect corals from mass discoloration due to climate change

US, WASHINGTON (ORDO NEWS) — Coral reefs around the world suffer from discoloration, which causes an increase in water temperature amid global climate change. Thus, the Great Barrier Reef in the Pacific Ocean recently experienced its third massive discoloration in five years – after the highest ocean temperature for this month was recorded in February this year.

The images showed that during the last two weeks of March, 25 percent of the reef was discolored strongly, another 35 percent – moderately. For the first time in history, the northern, central, and southern parts of the reef were simultaneously affected.

The fact is that when the oceans become too warm, corals – calcareous organogenic geological structures formed by colonial coral polyps and some types of algae – lose their multi-colored microalgae Symbiodiniaceae, which live in their tissues and serve as food for them. This leads to the fact that corals become discolored and eventually die of hunger.

Patrick Burger of the Australian Association for Scientific and Applied Research, along with colleagues from the Australian Institute of Marine Sciences (AIMS) and the University of Melbourne, wondered how corals can survive in warmer waters by increasing the thermal stability of their symbiotic algae.

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“The coral cover of the Great Barrier Reef declined by about half due to the summer heat in 2016 and 2017, followed by a 89% reduction in coral larvae in 2018. Although corals adapt to changing conditions, their rapid death indicates that the rate of climate change is ahead of the natural rate of coral adaptation, ”the scientists explain.

According to a study published in the journal Science Advances , the team isolated microalgae from corals and cultivated them in a specialized laboratory. Using a technique called “directed evolution,” they in vitro exposed cultured microalgae to higher temperatures — up to 31 ° C — for four years. As a result, algae developed genetic changes and were able to adapt to life in hotter conditions.

Then the researchers took the coral larvae of the Great Barrier Reef, mixed them either with ordinary algae or with heat-resistant ones and heated it again to 31 ° C for a week (it is at this temperature that the bleaching process begins). Coral, inside of which ordinary algae lived, eventually quickly lost its color, but coral with modified heat-resistant algae remained healthy.

“Our new approach enhances the heat resistance of coral by manipulating it with microalgae, which is a key factor in the heat resistance of coral,” says Burger. The authors note that the results of their work are already promising, but additional research is needed to check whether heat-resistant algae can be used to prevent discoloration not only in young but also in adult corals. In addition, you need to find out if this method works with different types of corals.

Burger also noted that fighting climate change remains the most important way to save reefs, but scientists are also developing “artificial” methods to protect corals – in case humanity fails to reduce greenhouse gas emissions and slow down global warming.

However, in May 2017, experts said that large-scale measures, which are planned to be sent to save the Great Barrier Reef until 2050, will not bring results. Experts stated: it will not work to save the reef and it is worth focusing on preserving at least its “ecological function”.


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