For the first time since systematic observations began, extensive mass bleaching of sponges has occurred in Fiordland, New Zealand – a phenomenon known hitherto primarily from overheated corals. Up to 95 percent of all sponges are affected in some areas, Scientists report on James Bell of Victoria University of Wellington in the “Guardian”.. This may be due to an intense local heat wave in the Pacific: average water temperatures in April were the highest in the area so far measured. The length and intensity of a heat wave off the southwest coast of the South Island has exceeded any event in at least 40 years.
Affected sponges are usually dark chocolate brown in color, but diving scientists are now finding specimens that are predominantly off-white. “Such damage has never been observed in New Zealand, and there have been few reports of such cold water incidents internationally,” Bell said. The working group estimates that there are hundreds of thousands of infected samples. Bell says there have been similar reports of sponge bleaching off the coast of Tasmania.
Until now, sponges have been considered relatively robust marine organisms that are more tolerant of changes in the ocean than corals. But this could change. This illustrates the kind of climate crisis we are dealing with. “There are so many species in New Zealand that we don’t know what their heat tolerance is,” Bell told the Guardian.
It is unclear whether the sponge directly suffers from overheating or whether the unusual temperatures make the animals more susceptible to disease due to the increased stress. It also remains questionable whether and when the animals will be able to recover. Sponges are among the main species in these marine ecosystems, building entire coral reefs.
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