Deep areas of coral reefs are invaluable to nature because they offer shelter against warm-water bleaching and intensifying storms — the impacts of climate change.
These deep reefs are no different from shallow reefs, and research has shown that they both share the same coral species.
This had scientists thinking: could deep reefs be a source of new corals to "reseed" destroyed shallow reefs?
Destroyed Shallow Reefs
In a new study, Pim Bongaerts and his colleagues from University of Queensland sought out to investigate the roles of deep reefs in helping damaged reefs.
Because it was impossible to track the movements of a single coral larvae, the team employed methods that analyzed the genetic similarity between coral populations to understand the relationship between deep and shallow coral reefs.
The group focused on the isolated Bermuda reef system in the Atlantic, screening more than 200 individual coral colonies from both deep and shallow water. These reefs belonged to two coral species that had the same depth distributions.
Researchers found that the relationship between deep and shallow reefs varied greatly between species and can be affected by natural selection.
Thus, the concept of deep coral reseeding may be effective to some species, but Bongaerts said it is "ultimately unlikely" to help in the broader recovery of shallow reefs.
Ove Hoegh-Guldberg, Bongaerts' co-author and a professor at the university's Global Change Institute, said deep reefs have provided hope in recovering damaged shallow reefs, especially those that were destroyed by extreme bleaching events.
However, he said the results suggest that the role of deep reefs in reseeding is likely to be limited.
Health And Growth Of Coral Reefs
Coral reefs benefit from a mutual relationship with fish, and this relationship may actually help heal damaged reefs, past studies have shown.
In August 2016, scientists discovered that the urine of fish provides vital nutrients that help coral reefs grow. When fish pee, they release nitrogen and phosphorus in the form of ammonium, which serves as nourishment for the reefs. This allowed researchers to hope that fish pee could help in the recovery of destroyed coral reefs.
Meanwhile, Bongaerts said the findings of their study underline the fact that because of increasing disturbances that coral reefs continue to face, it is unlikely that the problem will sort itself out.
He said if we wanted to have a chance of saving these ecosystems, it is important that we start reducing our carbon emissions and divest from use of fossil fuels. This will help save these dying coral reefs.
"The responsibility for their future lies with us," Bongaerts added. Details of the new study are published in the journal Science Advances.