Sponge networks could capture DNA to monitor the health of the oceans | Science

To track the biological health of the oceans, researchers are using cameras, satellite images and, increasingly, DNA poured directly into the water. But capturing genetic material at sea is a difficult task: scientists have to sift through huge amounts of water to extract their samples. Now, marine biologists have discovered that sponges are very effective at "mopping up" the DNA. More research is needed, but a network of sponges planted in the oceans could eventually help to better understand the diversity of the surrounding flora and fauna.

"It's a smart idea," says Eske Willeslev, an evolving geneticist from the University of Copenhagen who did not participate in the work. "This could make biodiversity studies easier and more consistent."

Biologists around the world are trying to list all the plants and animals in the world before they disappear. Traditionally, this meant going out and collecting samples of all species. In the past 20 years, however, researchers have collected and sequenced DNA from soil, water, air and even intestines from other organisms. This so-called environmental DNA, or cDNA, can indicate which plants, animals or microbes are present in a given environment.

In the United Kingdom, at the University of Salford, marine ecologist Stefano Mariani had focused his efforts on e-DNA on the marine environment. But he always found that sample processing was "tedious, cumbersome, stressful and unnecessary".

So he decided to see if the animals that filter the seawater for food could also be DNA tanks. He first tried the shrimp tripe, but since these invertebrates are difficult to eat, he decided that the DNA they were aspiring to do not reflect what existed. But sponges do not discriminate. "A sponge the size of a football can almost filter a pool in a day," he says. Mariani obtained the DNA of nine sponges from the Mediterranean and Antarctic and used them as a test. To see how the process could work for species conservation specialists, he tried to isolate all vertebrate DNA with the help of special molecular probes. The DNA can be in the terry cloth or particles trapped in its channels.

The results were even better than those expected by Mariani. With his colleagues, he isolated the DNA of 31 types of organisms, including Weddell seals, chinstrap penguins and cod, said today the team at Current biology. In addition, the Antarctic and Mediterranean sponges contained DNA from different groups of creatures, reflecting the different species that lived in both places. It was therefore easy to know where the sponge and the DNA came from.

Mariani says scientists could one day use these DNA capture sponges with robots and autonomous underwater vehicles to filter water and extract DNA. Robots and vehicles are promising, says Mariani, "but they are also big, expensive, and not the easiest to handle, transport, and maintain." If you could use sponges, even a citizen citizen could recover DNA data by simply cutting predicts a small piece of sponge.

Paul Hebert, a researcher on biodiversity at the University of Guelph in Canada, sees a limited application of sponges as sensors of biodiversity, because bottom creatures do not live on the high seas, where it is very difficult to study them. other ways. He also notes that, since all sponges filter water at different speeds, it can be difficult to compare different DNAe collections.

Still, Hebert thinks the new work is inspiring. "Forget the natural sponges," he says. "I like the idea of ​​a techno-sponge," a human version that would mimic real sponge techniques to capture a DNAe. He says that he can imagine that techno-sponge schools plying the seas or sitting on the bottom of the sea collect valuable data. And even if such sponges – or their natural cousins ​​- proved unworkable, adds Hebert, "it was fun to consider the possibility that the bottom of the ocean was littered with samples of 39, autonomous DNA. "