The sea off the coast of New Zealand (NZ) is typically filled with velvety brown sponges, but new images show these marine creatures have turned to a bone-white – and climate change is to blame.
Scientists found sponges are ‘dying by the millions’ in what is ‘the worst bleaching event on record.’
The discovery was first made last month when thousands of creatures, but experts say there could now be tens of million dead.
James Bell, a marine biology professor from New Zealand’s Victoria University. who investigating the mass die off, told DailyMail.com in an email: ‘We have never seen this before in NZ.
‘Sponge bleaching on a small scale was reported in Tasmania 4 years ago, but nothing like the scale we have seen in NZ. It has also been reported in the tropics before, but again not at the scale we have seen.’
Bleaching, which is caused by a stress event, cause sponges to lose their cells, leaving behind a bare skeleton – this is a similar process seen among coral.
Although sea sponges are small, they play a vital role in the marine ecosystem by providing food and shelter to other marine animals.
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The sea off the coast of New Zealand is typically filled with velvety brown sponges, but new images show these marine creatures have turned to a bone-white – and climate change is to blame
The damaged sponges, one of more than 800 species in New Zealand, were found in more than a dozen places near the Breaksea Sound fjord.
‘Importantly, for the sponges in Fiordland our research so far has shown that these sponges are still alive, they have have lost most of the photosynthetic symbionts inside the sponges, but they are still alive,’ Bell told DailyMail.com.
‘However, we are also finding that the sponges without their symbionts are more palatable to fish, so many of the of the bleached sponges may eventually be eaten.
‘The important thing about sponges is that they are are really important in filtering water and in doing so they filter all the small organisms like phytoplankton and bacteria out of the water column. In doing this sponges move lots of potential food material from the water to the sea floor.
Pictured is an image of an unbleached sea sponge
‘The waste products that the sponges produce as they feeds are then available to other tiny animals on the sea floor, which are subsequently eaten by things further up the food chain. So sponges form a really important link between the water column and the sea floor, and are an under-appreciated link in food chains. If you loose the sponges this will therefore impacts lots of other diversity that is associated with the sea floor.’
The bleaching event was caused by extreme temperatures, which have persisted since September of last year.
Scientists found sponges are ‘dying by the millions’ in what is ‘the worst bleaching event on record.’ The discovery was first made last month when thousands of creatures, but experts say there could now be tens of million dead
In 2021, global ocean surface temperatures were 0.65 degrees Celsius higher than the 20th century average.
And it was the hottest on record for the third year in a row.
‘At the northern and southern limits of New Zealand, we’ve seen the longest and strongest marine heatwave in 40 years, since satellite based measurements of ocean temperature began in 1981,’ said Smith, as The Guardian reported.
According to Bell, some sea sponges will bounce back after a day or a week that sees just above average temperatures.
‘It might be possible for the sponges to recover. We have shown the sponges still contain some symbionts (which what they have lost), so there is perhaps potential they could recover, and its also possible that those that remain could be more tolerant in the future to other heat waves,’ he said.
‘Probably the key thing they might need to recover is a break from any further heat stress in the next few years.’
The bleaching event is similar to what is killing off coral in the Great Barrier Reef, which experts warn could soon be completely destroyed by climate change.
In April 2021, a report showed revealed that if 2.7F (1.5C) degrees of warming continues, the world’s largest coral reef system will eventually perish.
The bleaching event was caused by extreme temperatures, which have persisted since September of last year
The natural wonder is expected to shrink, but if the Earth experiences warming of 3.6F (2C) only one percent of coral will remain.
Researchers say that immediate ‘transformative action’ to reverse global warming is the only option for saving the Great Barrier Reef, but reaching the goal seems to be ‘virtually impossible.’
However, the team also notes that with Earth’s current rates of emissions, it is likely we will surpass 2.7F (1.5C) by 2025.
When ocean temperatures are too high, corals expel their colorful symbiotic algae that provide them with food — turning them a bleached white.
The report, titled ‘The Risks to Australia of a 3C Warmer World,’ suggests Australia is headed for a climate disaster and that it will take the Great Barrier with it.
‘As the driest inhabited continent, Australia is highly vulnerable to the impacts of global warming,’ the report states.
‘The summer bushfires of 2019–20 in a tinder-dry country, or the three severe coral bleaching events within five years that caused a loss of over 50 percent of hard coral cover in the shallow waters of the Great Barrier Reef, demonstrate some of the consequences of a warming planet for Australia’s people, economy and environment.’