This underwater photo taken on April 5, 2024, shows bleached and dead coral around Lizard Island on the Great Barrier Reef, 270 kilometres (170 miles) north of the city of Cairns – Copyright AFP/File DAVID GRAY
Scientists from Ohio State University have found that Red Sea corals can endure warming seas but grow much smaller and weaken under long-term heat stress. This provides additional evidence as to the adverse impact of climate change upon the world’s oceans.
Whilst recovery is possible in cooler months, rising global temperatures may outpace their resilience, thereby endangering reefs and the people who depend on them.
By studying how six months of elevated ocean temperatures would affect a species of coral from the northern Red Sea called Stylophora pistillata, scientists found that although these organisms can certainly survive in conditions that mimic future warming trends, they do not thrive.
Corals bleach in warm ocean waters, making them particularly vulnerable as global temperatures rise due to climate change. — © AFP
Coral in decline
S. pistillata corals tend to be tolerant of high ocean temperatures, but when continuously exposed to temperatures of 27.5 and 30 degrees Celsius (81.5 and 86 degrees Fahrenheit) — baseline warming expected in tropical oceans by 2050 and 2100 — scientists saw various changes in coral growth, metabolic rates, and even energy reserves.
Stylophora pistillata, commonly known as hood coral or smooth cauliflower coral, is a species of stony coral in the family Pocilloporidae. It is native to the Indo-Pacific region and is commonly used in scientific investigations.
For instance, coral in 27.5 degrees Celsius waters survived, but were 30% smaller than their control group; those placed in 30 degrees Celsius waters wound up being 70% smaller.
According to lead researcher Ann Marie Hulver: “In theory, if corals in the wild at these temperatures are smaller, reefs might not be as diverse and may not be able to support as much marine life…This could have adverse effects on people that depend on the reef for tourism, fishing or food.”
Adverse impact
The research results suggest that even the most thermally tolerant coral species may suffer in their inability to overcome the consequences of warming seas.
The reseachers paint a more detailed picture of how coral reefs may look and function in the next 50 years. Ocean temperatures are expected to increase by 3 degrees Celsius by 2100, expecting coral reefs to predictably bend to projected climate models can be difficult, according to the researchers.
Redressing the impact
Gaining a more complex understanding of how warming waters can alter coral growth and feeding patterns may also better inform long-term conservation efforts.
Research paper
The findings appear in the journal Science of the Total Environment, titled “Thermally resistant coral Stylophora pistillata survives but does not thrive under chronic elevated baseline temperature.”