New research highlights the role of microorganisms in protecting corals from thermal stress
Researchers have discovered for the first time a single-celled microbe that can help corals survive ocean warming events such as bleaching. The new study, led by scientists from the University of Miami's Rosenstiel School of Marine, Atmospheric and Earth Sciences and the Institute of Evolutionary Biology (IBE: CSIC-UPF) in Barcelona, provides new information about the role microbes might play, designed to help corals withstand warming predictions at the end of the century.
Scientists have found that the abundance of certain protists in the coral microbiome – the various microorganisms that live within it – can indicate whether a coral can survive thermal stress. These findings have important implications for corals around the world as they more commonly face warming oceans, especially those without zooxanthellae, the symbiotic algae that are expelled from a coral during bleaching caused by warm water.
“This is the first time that a non-algae microbe has been shown to influence the ability of corals to survive an episode of thermal stress,” says Javier del Campo, lead author of the study and associate professor at the Rosenstiel School principal investigator of the IBE, a joint center of the Higher Council for Scientific Research (CSIC) and the Pompeu Fabra University (UPF). “As corals face increased heat stress due to climate change, a better understanding of all the microbes that can influence their ability to survive can inform conservation experts about which corals should be prioritized for interventions.”
To carry out the study, the international research team collected samples of corals from across the Mediterranean region to analyze their microbiome and conduct thermal stress experiments. They amplified and sequenced two types of rRNA to study the bacteria and protists present in the microbiome of a soft coral species, the fierce Fusta (Paramuricea clavata) before exposing them to natural heat stress in the laboratory to examine them for signs of mortality.
Paramuricea clavata is an important architect of temperate Mediterranean reefs that is currently threatened by mass extinctions linked to global warming.
The researchers found that a group of parasitic unicellular protists called Syndiniales are most common in corals that survive heat stress, while corallicolids, a group of protists closely related to the parasite that causes malaria in humans, are most common in Corals that survive heat stress die from thermal stress.
According to the researchers, protists, or single-celled eukaryotes, are less studied than bacteria in most host organisms, but can have a major impact on the health of their coral host.
“The microbiome is an essential part of the health of the host coral and we should study all of its members, from bacteria to protists,” says del Campo.
REFERENCE
Differential presence of apicomplexan predicts thermal stress mortality in the Mediterranean coral Paramuricea clavata in environmental microbiology.