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Sea sponge in New Zealand: Usually chocolate brown, latterly more commonly white
Photo: Nature Picture Library / IMAGO
The largest sponge bleaching ever recorded appears to have occurred off New Zealand.
This is reported by the British »Guardian«.
The newspaper refers to scientists.
As a result, extreme water temperatures have turned millions of aquatic creatures white.
Marine biologist James Bell of the Victoria University of Wellington spoke of the largest sponge bleaching ever found in the world.
Initially, members of Bell's team spotted individual white sponges.
In more than a dozen spots near the Fiordland region's Bracksea Sound and Doubtful Sound fjords, a research team from the college found the animals bone white instead of the normal chocolate brown.
The water was five degrees Celsius warmer than usual.
Later, crews from boats across the region reported bleached sea sponges.
These would have been pretty much everywhere they looked.
Sea sponges depend on organisms that carry out photosynthesis in them.
This creates food for the sponge and it can fend off enemies.
The bleach drives these organisms away.
This weakens the sponges' defenses and makes it harder for them to feed, but doesn't necessarily kill them immediately.
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.
According to the report, there had recently been two heat waves in New Zealand waters, with temperatures rising to record highs.
The water has not been this warm since 1981, when measurements began.
The heat wave lasted 213 days.
Globally, temperatures are also rising in the oceans - mainly because mankind burns oil products, gas and coal almost unchecked and thus emits carbon dioxide (CO₂) - for example in cars, airplanes, power plants and factories.
Globally, 2021 was the warmest year in the oceans since measurements began.
According to researchers, these heat waves are likely to increase and last longer.