Deep water reefs are unlikely to be safe harbors for many fish and coral species from shallow reefs threatened by climate change and human activity. Shallow water creatures may have trouble adapting to conditions in the deep, scientists report in the July 20 Science. Plus, deep reefs are facing the same threats that are putting shallower ones at risk.
The study deals a blow to the “deep reef refugia” hypothesis. That’s the idea that species from troubled shallow reefs could simply move to reefs at depths of 30 to 150 meters, called mesophotic reefs because they exist at the limits of where sunlight reaches. Even though individuals of a typical shallow water species may be spotted at a wide range of depths, it doesn’t mean the majority of that species could survive living in deeper waters, says study coauthor Luiz Rocha, a zoologist at the California Academy of Sciences in San Francisco.