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Fri, 2nd Apr 2021 10:56:00 |
Then and now: Rising temperatures threaten corals |
In our monthly feature, Then and Now, we reveal some of the ways that planet Earth has been changing against the backdrop of a warming world. Here, we look at coral bleaching, and how warming waters are threatening the survival of a true wonder of the seas.
Coral reefs are hives of activity in the ocean, where many different species can be found. Scientists refer to such zones as biodiversity hotspots.
Although reefs take up less than 1% of the area covered by ocean, they are estimated to be home to more than a third of life under the waves.
Yet they too face an uncertain future as a result of a warming world. Scientists list climate change as the main cause of damage to the world's reefs.
Corals can't tolerate very high temperatures, so as ocean water warms, they effectively become "sick". Thermal stress of this kind can lead to the coral becoming bleached, meaning they lose their striking colours and turn white or very pale.
Coral can survive bleaching events, but in this state they are also more likely to die.
The before and after photos show an episode of bleaching and coral mortality in American Samoa, a territory in the Pacific Ocean, back in 2015.
A US team of scientists observed at the time: "Severe bleaching and mortality occurred on shallow inshore and [lagoon] reefs along southern Tutuila [American Samoa's main island].
"These shallow habitats have limited water circulation, which worsens the effects of high temperature stress."
Despite this worrying event, the state of the reefs in this area are currently deemed to be "good".
Read original full article
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