For the sixth time, algae on the Great Barrier Reef has been wiped out due to increasing warm water and the picture isn’t pretty. The stress is turning the reefs white from the corals’ loss of their sensitive algae (zooxanthellae), which give them their color. Coral bleaching is a visible hallmark of the stress caused by climate change.
The reefs can die from the purging of zooxanthellae algae which feed the living coral.
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The Australian reef has been submerged in abnormally hot ocean temperatures running up to 7 degrees Fahrenheit above average and conditions have been extreme since November, which was the warmest November on record.
This bleaching event is even more significant coming on the heels of back-to-back mass bleaching in 2016 and 2017 and another in 2020. The years have left large parts of the Great Barrier Reef with only half of their live corals. For a reef that takes thousands of years to grow, the frequency of heat-related die-offs is too many to overcome.
The most sensitive corals are dying and those are the species more responsible for building up the reef profile.
This most recent bleaching occurring in the warmer months of the southern hemisphere resulted in 60 percent of the reef’s corals purged of the colorful algae.
Warming oceans are killing coral around the world including in Florida.
Coral bleaching in the Keys has been occurring for many years with the frequency and severity of these events steadily increasing since the 1980s.
The worst bleaching event ever documented in the Florida Keys came right after the second warmest winter on record in 1996/97. The most recent significant bleaching event in the Florida Keys occurred in 2005, and there have been mild localized bleaching events since then.
Last year was minor in comparison. The Florida Keys BleachWatch 2021 season totaled 210 reports that only had minimal signs of coral bleaching with only 1-10% of corals affected at most of those sites.