Massive bleaching of sea sponges can be devastating to New Zealand marine life
Marine scientists are worried about the ecosystem of our country’s largest national park, fearing that the mass bleaching of Fiordland’s native sea sponges is just the tip of the damage caused by climate change.
Researchers have discovered bleached sea sponges for the first time in New Zealand – and it’s not good news.
“It’s quite alarming,” says James Bell, professor of marine biology at Victoria University.
He says sponges, once healthy and brown, have been bleached out following a drastic change in temperature due to global warming, in some areas of Fiordland up to 95% of sponges are affected.
Laundering like this is a first in New Zealand – and rare in cold waters internationally.
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He says the true extent of the damage has yet to be discovered.
Sea sponges are an essential part of the Fiordland marine ecosystem, they provide habitat for organisms to live in and filter food for fish.
“Given the vast area in which this species occurs in Fiordland, you could be talking about hundreds of thousands or even millions of individual sponges that have actually been bleached.”
The heatwave may also have had a direct impact on other native marine species.
“It’s entirely possible that other species were affected by this heatwave, it just so happens that the bleaching and color change is very obvious to spot.”
The Fiordland Marine Guardians were established to advise the government on the management of the Fiordland marine area.
President Rebecca McLeod said the news came as a shock to the group.
“James Bell came to our meeting a few weeks ago and showed us some of the photos and videos and I think everyone was very quiet, but it took us a while to understand the seriousness of this discovery.
“We were hoping it would be a really localized mortality event, but it appears to be across the entire Fiordland marine area, which is a massive area of New Zealand’s coastline.
“Usually we feel quite helpless…it’s quite a crushing blow.”
The damage comes as climate change causes fluctuating ocean temperatures to rise in recent years.
Dr Robert Smith is a lecturer in the Department of Marine Science at the University of Otago and works with the government-funded Moana Project to record and study ocean temperatures.
He says marine heat waves are becoming more common as a result of global warming. In April, parts of the South Island were hit with some of the hottest waters on record.
“I was really surprised at how much these temperatures have warmed up, especially off the coast of Fiordland.
“The water temperature peaked at 5 degrees Celsius above normal, actual temperatures were around 20 degrees, and that’s a record for this time of year.”