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Bleached sponges have been discovered for the first time off the coast of New Zealand's South Island after an extreme rise in sea temperature.
In more than a dozen spots near the Fiordland region's Bracksea Sound and Doubtful Sound fjords, a research team from Victoria University of Wellington found the animals bone white instead of the normal chocolate brown, the Guardian reports.
In some places, more than 95 percent of the sponges have faded, said marine biologist James Bell.
"According to our first estimates, at least hundreds of thousands of sponges are probably pale, maybe even more."
The team discovered the mass bleaching on a research trip in April.
According to marine researcher Rob Smith from the University of Otago, the water temperatures in Fiordland at this time, actually autumn in the southern hemisphere, were still 5 degrees Celsius above the long-term average.
"This summer we had the strongest marine heat wave on the west coast of the South Island in 40 years." According to official data, the sea around New Zealand was around 2.6 degrees Celsius warmer than normal.
Globally, 2021 was the warmest year in the oceans since measurements began.
About 800 different species of sponges dominate the seabed around New Zealand.
Sponges are said to be adaptable compared to corals, which tend to fade en masse.
"This is a really unusual occurrence," Bell said.
The bleaching of the sponges had previously been detected off the Australian island of Tasmania. The measurement data were published in the scientific journal Climate Change Ecology.
The link between the heat wave and the bleaching of the sponges needs more research, Bell said.
However, there is a very strong correlation.
The find underscores “the climate crisis we are facing”.
It is not known what temperatures they can withstand for many species in and around New Zealand.
Some of the bleached sponges might survive when the water cools again, Bell said.
The team wants to check back on how the marine animals are doing at the end of the month.
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