Scientists have developed a novel tool designed to protect and conserve coral reefs by providing them with an abundance of feeding opportunities.
The device, dubbed the Underwater Zooplankton Enhancement Light Array (UZELA), is an autonomous, programmable underwater light that works to draw in nearby zooplankton, microscopic organisms that coral feed on.
After testing the submersible on two species of coral native to Hawaii over six months, researchers found that UZELA could greatly enhance local zooplankton density and increase the feeding rates of both healthy and bleached coral. Importantly, providing coral with greater amounts of food makes them stronger and more likely to be resilient against certain environmental threats, like heat stress or ocean acidification.
This result is impressive, especially at a time when rising ocean temperatures are forcing entire coral reefs to the cusp of collapse, said Andrea Grottoli, lead author of the study and a professor of earth sciences at The Ohio State University.
"Coral reefs house one-third of all marine species, yet occupy less than 1% of the ocean," she said. "They are disproportionately responsible for ocean health and we're at risk of losing them."
The study was recently published in the journal Limnology and Oceanography: Methods.
Millions of humans rely on coral reefs, as they support fishing industries and protect coastline communities from dangers like erosion and floods. Unfortunately, many climate models project that at Earth's current rate of warming, these vital coral reefs may be completely devastated by 2050, jeopardizing the complex ecosystems they sustain.
Although the technology in this study is only a short-term solution to the environmental threats that coral reefs face, the device will likely be very beneficial to coral restoration efforts, said Grottoli. "Think of it as a band-aid for about a couple decades," she said. "It can protect some corals in some places, sometimes."
The team also found that UZELA, which can be powered for half a year on a single battery, could optimize a coral's feeding time by operating for just one hour after dusk.
Understandably, artificial lights can disrupt the behavior of other marine animals, so researchers could choose not to use the device year-round. That said, the study emphasizes that corralling zooplankton with this human-made tool doesn't seem to harm the environment or interrupt the flow of other zooplankton in the surrounding area.
"If you imagine zooplankton in a column floating above coral, instead of being naturally dispersed, UZELA is just pulling them down, but it's not taking away from the coral beside it," said Grottoli. "We show that if you put the coral close to the light, they benefit from that concentrated zooplankton, and feeding rates go up 10- to 50-fold."
This number is equivalent to an 18-68% increase in the amount of metabolic demand that can be met by zooplankton alone, meaning that increased feeding helps supplement a large part of the coral's diet, which successfully leads to an increase in coral survivorship and persistence.
"The real intent of this project is to inject new technology and energy into coral restoration success," Grottoli said. "It's something that can be deployed strategically for high-value reefs, or projects that have already had a lot of investment in them."
Widely adaptable to various marine environments, UZELA can also easily be serviced by divers once placed in optimal underwater locations.
Notably, while the current generation of UZELAs are handmade, the team is working with an Ohio-based engineering company to redesign the technology to make it more manufacturable. Grottoli expects these more enhanced versions will be available within the next one to three years.
"We are not mitigating climate change fast enough to save coral, and UZELA is not going to instantly save coral reefs," she said. "But it is an exciting solution that will buy us time as we work toward a more sustainable environment."
Other co-authors include Shannon Dixon and Ann Marie Hulver from Ohio State as well as Claire Bardin, Claire Lewis, Christopher Suchocki and Rob Toonen from the University of Hawai'i at Manoa and the Hawaii Institute of Marine Biology.
The study was supported by the University of Hawai'i Foundation, the National Science Foundation and the Defense Advanced Research Projects Agency.
