Millions of sea sponges in New Zealand's Fiordland region have been affected by extreme ocean temperatures caused by global warming, per marine scientists.

The country has seen its worst mass bleaching event in 2022, with images showing once-brown sea sponges bleached bone white. While bleaching does not necessarily kill the sponges, it does deprive them of food by lowering their defences.

Sea sponges are found on ocean floors, and are filter feeders. This means they filter water through their bodies and gain nutrition by picking up food that passes by them.

Many invertebrates, such as corals and sponges are important ecosystem engineers, providing a framework for other animals to inhabit. These corals and sponges perform a similar role to that of rainforest trees.

"They pump out large volumes of water and capture tiny particles, bacteria, plankton and algae and also recycle carbon on the sea floor," said James Bell, a marine biology professor from New Zealand's Victoria University.

"They also provide shelter for marine creatures and increase habitat areas of the sea floor. They are very underappreciated creatures," he added.

Other parts of New Zealand, including its northern coastal areas, have also discovered thousands of dead sea sponges in the last few months. Some of them were even found "melting" due to extreme temperatures.

New Zealand has seen its longest marine heatwaves for the first time in 40 years, per the experts at University of Otago. The experts have warned that if steps are not taken to immediately control global warming it will have catastrophic impact for everyone.

"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," oceanographer Dr Robert Smith told The Guardian.

Oceans soaking up 90 percent of the excess heat from global warming has caused marine heatwaves that are killing marine species every year. According to a report in CNN, last year was the hottest year for the world's oceans.

The Great Barrier Reef has now suffered three mass coral bleaching events in the past five years. Photo/Great Barriier Reef Marine Park / -