Climate Change Modifies Reef Composition

Gorgonians are replacing scleractinian corals that are disappearing from marine ecosystems due to human impact and global climate change. This is the result of a study carried out by researcher of the Institute of Science and Environmental Technology of the Universitat Autònoma de Barcelona (UAB) Sergio Rossi, which analyzes the reason why the gorgonians (or octocorals) are proving to be one of the "winning" species in this transition process triggered by the spiraling death rates and degradation of corals in the deep sea and reefs.

It is estimated that after the last El Niño event (2015-2016), 50% of Australia's coral reefs are no longer functional: corals have died or been severely damaged. Climate change is eroding at all levels the most complex systems, such as reefs created by scleractinian corals, which are efficient animals that capture light through their symbionts (microscopic algae) to nourish themselves and build "stone". That same "stone" (the hard part of the coral, formed by calcium carbonate) is partly responsible for the high rate of algae photosynthesis, which supply up to 95% of the nutrients the animal needs to live.

"What is going on? Although the light may remain fairly constant, the sea temperature has risen", explains Rossi. The higher the temperatures, the more acceleration of the metabolic processes related to the photosynthetic process, to the extent that toxic molecules are created. The excess toxicity caused by the algae bothers the coral ... or the algae itself, it is not clear. What is clear is that when the temperature is too high, the algae simply leave the coral. This process is known as bleaching. And without algae, with only 5-15% of nutrients, the coral dies.

Read more at Universitat Autònoma de Barcelona

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