Skip to content

Record-high ocean temperatures hurting coral reefs: B.C. study

Coral reef ecosystems are worth US $375 billion annually, and are a key source of food and income
A reef on Kiritimati (Christmas Island). (Danielle Claar/Contributed to Black Press Media)

New research shows the effects of marine heatwaves caused by climate change on corals and biodiversity are worse than previously thought.

The research, published earlier this month by the University of Victoria, provides important hints about broader coral diversity and marine ecosystem health as the world is battling with record-breaking ocean temperatures.

Samuel Starko, a former University of Victoria postdoctoral researcher who is currently at the University of Western Australia, says the study focused on the epicenter of Kiritimati, a coral atoll in the central equatorial Pacific Ocean. It found three genetic lineages among one species of lobed coral and determined they reacted differently to extreme heat.

“Even though the lobed coral appeared to be the most resilient of all coral species, our results demonstrate that one lineage was actually very sensitive and experienced a major reduction in abundance following the heatwave,” Starko said.

“This highlights how the impacts of extreme events caused by climate change may be even worse than previously thought because they threaten diversity at the genetic level.”

Julia Baum, professor of ocean ecology and global change at UVic, researched these impacts and recently published a paper titled: “Marine heatwaves threaten cryptic coral diversity and erode associations amongst co-evolving partners.”

Baum says cryptic diversity can be important for the functioning of ecosystems.

“Reductions in the diversity of genotypes or lineages may limit the capacity for future adaptation that could help corals withstand, for example, disease or the effects of climate change,” the paper reads.

READ MORE: Canadian environmental groups praise UN accord to protect marine life on high seas

These heatwaves are important specifically towards coral reefs, due to them being highly sensitive to small changes in the temperature of their surrounding waters. During marine heatwaves, corals release algae that make them turn white, ultimately causing them to die from starvation.

Worldwide, coral reef ecosystems are worth approximately US$375 billion annually and are a vital source of food and income for hundreds of millions of people in tropical island nations.

Starko says the study’s identification of different coral genotypes highlights the potential for increasing coral reef resilience to threats, while Baum states this isn’t enough to protect corals and ocean biodiversity.

“We need to rapidly reduce greenhouse gas emissions to curb planetary warming. The current warming in Florida underscores that the ocean is simply becoming too hot for corals, and we need to act now to mitigate climate change,” Baum said.