Bleached Sea Sponges Found In Southern NZ As Ocean Temperatures Hit New Highs
Sea sponges off New Zealand’s southern coastline have been found bleached bone-white for the first time, following extreme ocean temperatures. A group of scientists from Victoria University of Wellington were alarmed to discover the sponges, which are typically a rich chocolate brown, were bleached in more than a dozen sites near Breaksea Sound and Doubtful Sound in Fiordland. The university’s marine biology professor James Bell said in some parts as many as 95% of the sponges were bleached.
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Last year, the world’s oceans were the hottest in recorded history, due to climate change, which among other things can cause the oceans to acidify and degrade reefs and ecosystems. New Zealand was no exception, with 2021 its hottest year on record. Temperatures in April were still unseasonably high, with coastal water temperatures up to 2.6 degrees above average, according to the National Institute for Water and Atmospherics.
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There have been reports of sponges bleaching, including off the coast of Tasmania earlier this year, but typically they tend to be more tolerant to oceanic changes compared with other species such as corals, Bell said. “It’s a really unusual event,” he said. “This just highlights the kind of climate crisis that we’re facing. There are so many species around New Zealand and we don’t know what their thermal tolerances are.”
In Fiordland, those temperatures were even higher, said Rob Smith, a University of Otago oceanographer, who works with the government-funded Moana Project researching marine heatwaves. He told RNZ the region recorded temperatures up to 5 degrees higher than usual. “What we’ve seen this summer is the strongest marine heatwave on the west coast of the South Island in 40 years.” Further research was needed to establish definitively whether ocean temperatures are causing the bleaching, Bell said. At this stage the researchers had an observation and a “very strong correlation” between the bleaching and a severe temperature spike.
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https://www.theguardian.com/world/2022/may/16/bleached-sea-sponges-found-in-new-zealand-waters-for-first-time