An underwater light device can ramp up coral feeding rates by up to 50 times, offering a potential lifeline to ecosystems teetering on collapse. The Underwater Zooplankton Enhancement Light Array (UZELA)—about as big as a flashlight—uses programmed light pulses to attract nutrient-rich zooplankton, enabling even heat-stressed corals to regain strength. As ocean temperatures soar and reefs bleach globally, this technology could buy critical time for corals.
Recently described in a paper in Limnology and Oceanography: Methods, UZELA can attract plankton densities up to seven times higher than surrounding waters, effectively serving corals a high-protein meal. Led by earth sciences professor Andréa Grottoli at The Ohio State University, the research shows that bleached and healthy corals alike can boost feeding by 10- to 50-fold under UZELA’s glow—potentially increasing the coral’s ability to withstand heat stress.
The researchers note in their abstract:
To leverage the advantage that zooplankton feeding has on coral resilience, we developed the Underwater Zooplankton Enhancement Light Array (UZELA). UZELA is a patented autonomous, submersible, and programmable underwater light that is deployable for 6 months on a single battery. With 1 h of operation per night, it locally concentrates naturally occurring zooplankton, providing corals with greater feeding opportunities. Field tests show that UZELA increases local zooplankton concentrations by sevenfold compared to adjacent non-UZELA controls and coral feeding rates by 10 to 50-fold in both healthy and bleached Montipora capitata and Porites compressa corals compared to conspecifics without UZELA.
Photographs of UZELA (Underwater Zooplankton Enhancement Light Array) (Grottoli, Jackson, and Steck 2023, PCT/US2023/078357): (a) top view of the lens cap (7 cm diameter) and (b, c) side views (20 cm tall). Photos by AM Hulver. Published in Liminology and Oceanography: Methods.
In field trials off Hawaii, Grottoli’s team found that corals near UZELA devices rapidly captured extra food, fortifying energy reserves needed to survive bleaching events. The team tested the device on Montipora capitata and Porites compressa—two major reef-building corals in Hawaii—which differ in how they respond to heat stress. By shining the small, upward-facing LED for just one hour after dusk (pictured above), the device minimizes disruption to other marine life while channeling nearby zooplankton toward the corals. The result: corals can meet up to 68% more of their metabolic demand through zooplankton feeding alone. That increase can be crucial when photosynthesis falters during warming events.
Zooplankton naturally migrate toward light at night, so the programmed LED simply takes advantage of this behavior. The light shines upward and only operates for about an hour per night, reducing any risk of confusing or disrupting other nocturnal marine species.
Coral reefs house one-third of all marine species, yet occupy less than 1% of the ocean. They are disproportionately responsible for ocean health and we’re at risk of losing them.
The researchers note in the paper that the technology is not a replacement for cutting carbon emissions or addressing local pollution.Instead, they frame it as a stopgap that buys time for coral species at highest risk. Because it can operate for half a year on a single battery and is compact, UZELA can be deployed in nurseries or restoration sites to nurture coral fragments until they’re large and robust enough to be transplanted. The paper also notes taht UZELA doesn’t appear to reduce zooplankton elsewhere on the reef
[Coral bleaching infographic from NOAA]
