If you're hoping that reef-restoring coral larvae will settle down in damaged reefs, you can't just sit around and wait for it to happen. You have to get out there and entice the larvae, which is exactly what a new algae-based gel is designed to do.
While we may think of coral reefs' "skeletons" as being composed solely of calcium carbonate produced by coral polyps, much of the material is in fact generated by what are known as crustose coralline algae.
Along with contributing greatly to the structural integrity of reefs, the algae-produced calcium carbonate also serves as a home to planktonic coral larvae. Once those formerly free-swimming organisms settle in and become polyps, they start producing reef-building calcium of their own.
It's a good arrangement for the coral, but it also benefits the algae.
Not only does the reef itself provide the algae with protection from the elements, the coral polyps also emit ammonia which the algae feed upon. It is therefore in the algae's best interest to entice any coral larvae that may be swimming past in the water column. In order to do so, the algae release metabolite chemicals that attract the larvae.
Led by Dr. Daniel Wangpraseurt, scientists at UC San Diego's Scripps Institution of Oceanography have now incorporated those metabolites into a gel that can be applied to degraded coral reefs. Called SNAP-X, the substance reportedly boosts coral larval settlement by up to 20 times as compared to untreated surfaces.
If the algae metabolites were just applied to the coral on their own, they would soon dissipate in the water, leaving the coral larvae unable to follow them to their source. For that reason, the researchers started by encasing the chemical molecules in durable silica nanoparticles. Those particles were then suspended within a biocompatible liquid blend of gelatin methacrylate and polyethylene glycol diacrylate.
When that liquid is sprayed or painted onto a surface – such as a piece of dead coral – then exposed to ultraviolet light, it polymerizes into a hydrogel form. That gel is capable of clinging to the surface for up to one month while immersed in flowing water, gradually releasing its larvae-attracting nanoparticles as it does so.
Initial lab tests showed that application of SNAP-X resulted in a six-fold increase in larval settlement. Subsequent tests that more accurately simulated the water flow on coral reefs, however, produced the 20-times figure.
It should be noted that all of the tests conducted so far have involved a single type of coral, but Wangpraseurt believes the technology should work on other species with a few tweaks.
"I think this material is a breakthrough that can hopefully make a big contribution to coral restoration," he says. "Biomedical scientists have spent a lot of time developing nanomaterials as drug carriers, and here we were able to apply some of that knowledge to marine restoration."
A paper on the research was recently published in the journal Trends in Biotechnology.
Source: University of California, San Diego