Corals and algae in Indian Ocean may survive future global warming

A team of scientists has discovered a diversity of corals harboring unusual species of symbiotic algae in the warm waters of the Andaman Sea in the northeastern Indian Ocean, which spells hope of resilience to future global warming. 

The discovery was made by researchers from Penn State University and their international collaborators.

"The existence of so many novel coral symbioses thriving in a place that is too warm for most corals gives us hope that coral reefs and the ecosystems they support may persist - at least in some places - in the face of global warming," said the team's leader, Penn State Assistant Professor of Biology, Todd LaJeunesse. 

Corals are colonies of tiny animals that derive nutrients and energy from golden-brown, photosynthetic algae that live inside the corals' cells. 

"This symbiotic relationship is sensitive to changes in the environment," said LaJeunesse. 

"An increase in sea-surface temperature of just a few degrees Fahrenheit for a period of several months can cause many of the coral-algal symbioses to break down and the algae to be expelled," he said. 

LaJeunesse said that continued global warming eventually may cause the demise of coral-reef ecosystems, which would have major impacts on the tourism and food-fisheries industries. 

According to team member Ove Hoegh-Guldberg, a professor at the University of Queensland in Australia, coral-dominated reefs may become scarce within the next 30 to 50 years, given the increase in the number of bleaching events that recently have taken place.

"The fact that the Andaman Sea and other regions around Southeast Asia are home to such a high diversity of corals is surprising because the water there is so warm and sometimes murky," said LaJeunesse. 

"The inshore locations we surveyed are not the sort of places where you would expect to see thriving coral communities.  Not only is the water warm and murky, but the tidal flux is so great that many of the corals can spend hours out of water, exposed to the harsh sun and dry air," he added.

The team identified the species of algae that associate with corals, as well as giant clams, sea anemones, zoanthids, and other reef-dwelling animals that form close symbiotic relationships with the single-celled algae that are referred to as zooxanthellae.

In the Andaman Sea, the scientists found a variety of seemingly thermally tolerant algae species, with one species being particularly abundant. 

"The species appears to have saved certain colonies of coral from the damaging effects of unusually warm water," said LaJeunesse.