Coral reef halos, also known as grazing halos or sand halos, are bands of bare, sandy seafloor that surround coral patch reefs. These features, clearly-visible from satellite imagery, may provide a window into reef health around the world, according to a recently published study by researchers at the University of Hawai’i at Mānoa School of Ocean and Earth Science and Technology (SOEST).
Coral reef halos, also known as grazing halos or sand halos, are bands of bare, sandy seafloor that surround coral patch reefs. These features, clearly-visible from satellite imagery, may provide a window into reef health around the world, according to a recently published study by researchers at the University of Hawai’i at Mānoa School of Ocean and Earth Science and Technology (SOEST).
Scientists have observed reef halos for decades, mostly in the tropics, and explained their presence as the result of fish and invertebrates, who typically hide in a patch of coral, venturing out to eat algae and seagrass that cover the surrounding seabed. But the fear of predators keeps these smaller animals close to the safety of the reef—and focused on eating the marine plants nearby.
In the recently published study led by Elizabeth Madin, associate research professor at SOEST’s Hawai’i Institute of Marine Biology, the team analyzed very high resolution satellite imagery and historical aerial imagery from the 1960s from around the globe. They documented the previously-undescribed presence of halos outside of the tropics surrounding seagrass “reefs,” and revealed the timescales over which coral reef halos change, merge, and persist.
