Randi D. Rotjan – Associate Research Scientist at New England Aquarium
On the eve of Charles Darwin’s birthday, Dr. Rotjan spoke at the Tufts Environmental Studies Lunch & Learn last week on the effect of El Niño and global warming on topical coral reefs and fish populations in the islands of Kiribati. Kiribati is a nation of scattered islands across thousands of miles of the Central Pacific with a population of just over 120,000. The Phoenix Islands, the worlds deepest UNESCO World Heritage Site, comprise 33 of these islands in roughly the area of the continental United States.
An Introduction to Coral:
Coral are plant-like animals, but they are animals in the Anthozoa class. They survive through a symbiotic relationship with various Symbiodinium species, which photosynthesize and transforms calcium minerals from the ocean into the calcium carbonate that forms the backbone of coral structure.
El Niño Warming Events:
During El Niño periods between 2002-2003, 2010, and 2015, ocean waters warmed enough to kill off significant portions of the Phoenix Islands’ coral. Corals turn white and die, a process called bleaching. Dead coral is then covered by an algae, which serves to feed fish populations, who can remain living in the protective skeleton of the dead coral. Eventually, a different, pink, algae invades, which serves as a food for baby corals. This marks a certain amount of resilience in coral populations. After the 2002 and 2010 bleaching events, when nearly 100% of coral had been destroyed, it had almost completely recovered before the 2015 El Niño. Interestingly, research has shown that the presence of shipwrecks tends to inhibit coral recovery. Further research is going to bring more of a focus on the local human impact, and the team is bringing an anthropologist on their next trip.