Find the link between climate change and the ocean

Sea sponges are very important to marine ecosystems. They play an important role in the oceans, as they provide shelter and food for most sea creatures, recycle nutrients by filtering thousands of liters of seawater each day, and host microbes that may be the key to some of the most pressing medical problems. challenges we face today.

Now, scientists from UNSW have found that when a tropical sea sponge is exposed to warmer temperatures, it loses important microbes, which could explain why sponge tissue dies. The most recent study, published today in ISM Communicationhave revealed that by exposing marine sponges to a temperature increase of 3°C, an important microbe leaves the sponge, potentially causing tissue poisoning.

A collaboration between researchers from UNSW, Heidi Luther from the Australian Institute of Marine Science and James Bell from Victoria University of Wellington, has added an important piece to the puzzle about the impact of climate change on sponge populations around the world.

“We’ve seen ocean heatwaves wiping out sponges in the Mediterranean and impacting sponges in New Zealand,” said Dr Emmanuelle Botte, from the School of BEES and lead author of the study.

“We saw that some species of sponges are not as resilient as we first thought to climate change. This research reveals that breaking the symbiosis between the host and the microbe can create a chemical imbalance in the sponge and lead to decay.”

Living in symbiosis with microbes

Sea sponges – ancient sea-dwelling creatures – are often mistaken for plants, but they are sedentary animals, and are actually some of the oldest on Earth.

“Sponges are 545 million years old,” says Dr Botte. “They live in symbiosis with microbes, which fulfill important roles for sponges: they recycle nutrients, generate energy, and protect sponges from predators and disease. Some microbes even detoxify the body of a sponge. They’re a bit like the liver and kidneys of a sponge.”

This important relationship between sponges and microbes is well documented. And research also shows that some species of sponges and related microbes are particularly vulnerable to warmer water temperatures.

“We undertook this study because we knew that some sponges are sensitive to future climatic conditions, but we wanted to know why,” said Dr Botte.

“Just like you and me, sponges need a healthy microbiome to survive. We suspect that changes in microbes and, more importantly, what they do to sponges, may explain why some species of sponges struggle in warmer waters.”

Shifts in the microbial makeup of sponges

“You can find sponges everywhere on the ocean floor – from the tropics to the poles,” said Dr Botte. This study focuses on sponge species commonly found on the Great Barrier Reef and in the western Indo – Pacific ocean – Stylissa fan shape.

The team analyzed the microbial makeup of these sponges, which are known for their sensitivity to increased temperature between 28.5°C and 31.5°C.

“Under these same conditions, we saw that there were large differences in the types of microbes found in healthy sponges in cooler temperatures, and in necrotic, or dying, sponges in warmer waters,” said Dr Botte.

One change in particular stands out. “A group of microbes known as archaea represent 10% of all microbes in healthy sponges. And we couldn’t see it at all in the necrotic sponge.

“We found that these microbes were the only ones that could detoxify the ammonia produced by the sponge. And without these microbes, toxic ammonia would accumulate in the tissues.”

It appears that the symbiosis between Stylissa flabelliformis and its microbes is not flexible enough to adapt to the high temperatures that are expected to average out by the end of the century.

Importantly, the potential impact of water warming on marine sponges and microbes is not a distant prospect. “We used conditions that not only represent future averages, but today’s extremes, as we have seen temperatures of 1.5°C-3°C above normal for many weeks in Australia,” said Dr Botte.

Gold mine for drug molecules

“Apart from providing food and shelter for other organisms, sponges are important for drug discovery,” said Dr Botte.

“In the oceans, most of the molecules that have antitumor or antipathogenic properties are produced by marine invertebrates, and in particular, by microbes that live in symbiosis with sponges,” said Dr Botte. “This symbiosis is the key to healthy oceans and a goldmine for molecules of pharmaceutical and commercial importance.”

The research team behind this latest work wanted to emphasize the risks climate change poses to microbial diversity on Earth. “Climate change doesn’t just impact big charismatic animals. There is a risk of eroding the biodiversity of simple animals and the microbes they host, which is key to the health of the oceans and life more generally on our planet.”