Which corals can withstand the heat of climate change? UM study has clues
For coral scientists trying to save the world’s reefs from climate change, the big existential question is: how to help these vital ecosystems withstand the heat of a warming ocean and resist a damaging effect called bleaching.
In a new study conducted by the Shedd Aquarium and the Rosenstiel School of Marine and Atmospheric Science at the University of Miami, scientists have attempted to understand why some coral colonies and even some corals tolerate heat better than others. The increasing heat increases the frequency of bleaching, when corals are injured by changes in conditions like temperature, light or pollution, and expel their symbiotic algae, causing them to turn completely white.
They examined 229 colonies in six locations where coral nurseries with endangered staghorn coral were built on the coast of Florida from Broward to the Keys. Together, these nurseries constitute the largest single-species coral restoration program in the world. The study was published this week in the Proceedings of the Royal Society B: Biological Sciences.
Using portable stress tanks constructed from coolers, scientists exposed corals to different temperatures and measured the heat stress each coral could withstand before showing signs of bleaching.
The information from this heat tolerance census will help organizations working to restore reefs with heat resistant corals and increase their chances of survival. Although this type of study has been carried out with colonies in the wild, this is the first time that a census has been carried out on corals grown in nurseries for restoration purposes.
“Knowing which corals are the most heat tolerant will save us a lot of time in restoration projects. With these tests we can tell which corals are winners and good candidates for breeding and other restoration efforts, ”said Andrew Baker, professor in the Department of Marine Biology and Ecology at UM Rosenstiel School. and co-author of the study. “And it’s a quick test, we can get results in a matter of days.”
During two research expeditions on a Shedd research vessel in August and October last year, scientists collected coral fragments and placed them in tanks constructed from eight regular 24-can coolers. They were fitted with an aquarium heater and cooler, and seawater circulated through each cooler with pumps.
The coral fragments have been exposed to temperature increases from a baseline of 30 degrees Celsius (86 Fahrenheit) up to 38 degrees. The results allowed scientists to identify more resilient colonies and individual corals. Variation has sometimes occurred within nurseries, among corals close to each other, Baker said.
Although this study was performed in Florida, Baker said scientists and managers are increasingly interested in studying heat tolerance in other populations of corals around the world. The research provides a model for further efforts to identify heat-tolerant corals and gives significant impetus to restoration programs trying to stem the sharp decline of reefs due to climate change.
Scientists from Australia to the Keys rush to restore reefs as climate change, more frequent bleaching events, increased coastal development, pollution and overfishing are killing corals at an alarming rate.
In Florida, warmer temperatures cause nutrient-rich waters to produce more algae, which can choke corals. Dredging has affected the settlements, and the increase in boat and ship traffic around the Florida Reef has also taken a heavy toll on the corals. In recent years, a mysterious disease that erupted about five years ago off Virginia Key has started to spread very rapidly along the coast. In June, it reached Dry Tortugas, where scientists last year collected healthy corals to add to coral labs across the country to create a gene bank for restoration efforts.
Nova Southeastern University, the Mote Marine Laboratory, the Florida Fish and Wildlife Conservation Commission, Reef Renewal, and the Coral Restoration Foundation participated in the study.
This story was originally published October 21, 2021 2:59 pm.