Scientists invent underwater umbrellas to protect coral reefs

Researchers tested simple “underwater umbrellas” that shade individual corals to reduce sunlight-driven stress during marine heatwaves and found measurable protective effects. Built from pipes and nylon cloths anchored to the seabed so the canopy floats about 30 cm above the coral, 20 shades were deployed over 10 colonies of two brain-corals (Pseudodiploria clivosa and Colpophyllia natans) at Newfound Harbor in the Florida Keys in summer 2024, with 20 matched unshaded controls. The shades cut light exposure by roughly 60%; divers monitored color and took biweekly tissue biopsies. During one of the region’s strongest heat-stress events, shaded corals bleached less than unshaded ones and some regained color, and none of the corals in either group died.

The experiment, published in Frontiers in Marine Science and led by Karen Neely, functions as a proof-of-concept for protecting high-priority, small reef areas such as nurseries or individual colonies. Unexpectedly, unshaded corals also bleached less than anticipated, likely because many hosted the heat-tolerant symbiont Durusdinium; researchers saw no clear differences in algal density or species between groups, possibly because permitted biopsies sampled colony edges that are less sun-exposed. The team found no evidence of ecosystem harm and suggests engineering adaptations could scale the approach, but emphasizes the need to test longer-term effects on disease, growth, and reproduction.