Hydrogel helps coral find new home

When baby corals are hunting for a new home, they float around the water column until they find somewhere to settle down and hopefully to grow big and strong. To find a suitable spot to grow, larval corals rely on chemical cues released by their relatives.

“But if you’re on a degrading reef, a dying reef, or if you are creating an artificial reef, there are none of these chemical signals,” says Daniel Wangpraseurt, an interdisciplinary marine biologist at the Scripps Institution of Oceanography at the University of California San Diego.

Wangpraseurt and his lab team have made a gel that they can paint onto reef surfaces to mimic coral suitability signals. They say the gel, which they hope will help coral restoration and engineering, helps achieve a rate of coral settlement up to 20 times as great as that on untreated surfaces (Trends Biotechnol. 2025, DOI: 10.1016/j.tibtech.2025.03.019).

Inside the hydrogel is a suite of chemical compounds extracted from crustose coralline algae (CCA). Samapti Kundu, a materials scientist and postdoctoral researcher in the Wangpraseurt lab, says that those chemicals consist mainly of lipid-like molecules, steroid lactones, and carbohydrates. “We encapsulate those chemical cues in a nanoparticle system and mix them with a hydrogel biopolymer–like system,” she says.

After spraying, painting, or pipetting the gel onto a substrate for the corals to grow on, the researchers use ultraviolet light to cure and harden it. The hydrogel then slowly releases the chemical cues over a month or more to convince coral larvae to settle on the surface it was applied to.

Wangpraseurt says coral reefs can attenuate up to 90% of the energy from waves in the ocean. That’s why he’s interested in helping develop hybrid reefs, in which corals live on artificial structures, to help protect coastlines that don’t have healthy reefs already in place. Wangpraseurt and Kundu say their gel can help larvae settle on these structures.

“One of the reasons we created this material was originally for the US military, who was looking for effective coastal resilience solutions that are self-healing and living,” Wangpraseurt says. The researchers are now actively commercializing their hydrogel technology via their start-up, Hybrid Reef Solutions.

Mikhail Matz, a coral genomicist at the University of Texas at Austin who wasn’t involved in this research, says that it’s a standard practice to use CCA extract to aid larval recruitment in a laboratory setting but that it’s much more difficult to use those extracts in the field. And he thinks that’s where this gel could have real utility.

But first Matz would like to see a comparison of larval settlement rates of the gel with the ethanol metabolite extractions he uses in his lab, as he thinks comparing the treatment with no treatment at all, as was done in the paper, isn’t the fairest comparison. “The larvae generally don’t settle without a cue,” he says.

To make the treatment even more sustainable, Matz also thinks there would be a benefit in developing a hydrogel that doesn’t require using CCA extract and that is effective at recruiting coral species that use a different cue. “If it was a fully synthetic thing, that would be great because that would be really scalable,” he says.