New Zealand sees record bleaching of sea sponges

Wellington, June 23 New Zealand is witnessing, what scientist say, the largest bleaching of sea sponges due to extreme ocean temperatures which turned millions of the aquatic creatures white.
Initially, researchers estimated hundreds of thousands of the sponges had been bleached – but over the past month, scientists conducted investigations at coastlines around the country, and found that millions – possibly tens of millions – had been transformed bone-white, The Guardian reported on Thursday.
In the last month, the researchers had raised the alarm, when they, for the first time, found sea sponges bleached off New Zealand’s southern coastline.
Marine ecologist Professor in Victoria University James Bell said, “As far as we’re aware, it’s the largest scale and largest number of sponges bleached in one event that’s been reported anywhere in the world … certainly in cold waters.”
In May, when Bell’s teammates had found the bleaching event in Fiordland for the first time, they informed the Conservation Department and other charter vessels around the region to see if it had been spotted in other Sounds, according to The Guardian.
“They pretty much reported the bleaching everywhere they went,” he said. The team now believes “there are at least millions of sponges, maybe many millions of sponges that have undergone this bleaching”.
Sea sponges, like coral, rely on symbiotic organisms that photosynthesise inside them, providing food for the sponge and sometimes deterring predators.
While bleaching does not necessarily kill the sponges outright, it evicts those organisms – lowering the chemical defences of the sponges and depriving them of food. While some species can recover from severe bleaching, Bell said others do not.
University of Otago oceanographer Robert Smith said, “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,” he said.