A new study led by researchers at Lancaster University has found that the presence of seabirds on islands adjacent to tropical coral reefs can boost coral growth rates on those reefs by more than double. In addition, coral reefs near seabird colonies can bounce back much quicker from bleaching events, which often cause mass die-off of corals when seas become too hot.
The researchers found that Acropora around islands with seabirds recovered from bleaching events by around 10 months faster compared to reefs located away from seabird colonies. The key to how seabirds can help tropical coral reefs to grow and recover more quickly is through their droppings. The birds feed on fish in the open ocean far from islands, and then return to islands to roost—depositing nitrogen- and phosphorus-rich nutrients on the island in the form of guano. Some of the guano is washed off the islands by rain and into the surrounding seas where the nutrients fertilise corals, and other marine species.
“Our results clearly show that seabird-derived nutrients are directly driving faster coral growth rates and faster recovery rates in Acropora coral,” said Dr. Casey Benkwitt, research fellow in coral reef ecology at Lancaster University and lead author of the study. “We’ve been able to show a clear link between the presence of seabirds and faster coral growth. This is really exciting and encouraging that a natural solution is available to help boost the resilience of coral reefs in the face of a warming planet.
[image: Acropora coral at study site. Credit: Dr Cassandra Benkwitt]