Researchers at the Smithsonian Marine Station in Fort Pierce, Florida, have made strides in combating stony coral tissue loss disease, a lethal affliction affecting coral populations since its emergence in Florida in 2014. Characterized by white lesions leading to the loss of polyps that comprise the coral, the disease has spread throughout the Florida Keys and the broader Caribbean. With its precise cause still unidentified, scientists suspect a bacterial origin. As the disease progresses, it leaves behind only the stark white skeletons of the corals, significantly impacting marine ecosystems.
In an innovative approach to mitigate this crisis, researchers have turned to probiotics—beneficial bacteria that can combat pathogens or perhaps stimulate the coral’s immune responses. Traditional antibiotic treatments, while offering a quick fix, pose a risk of antibiotic resistance and do not provide long-term protection against reinfection. In late 2020, the research team conducted a pilot study testing probiotics on 30 infected great star coral colonies, identifying promising results in halting disease progression.
The star of their experiment was a specific bacterium named McH1-7, isolated from coral fragments exhibiting resistance to the disease. Microbiologist Blake Ushijima’s work focused on these beneficial microbes, noting that they create antibacterial compounds that could neutralize disease-causing bacteria. The research team developed a probiotic paste containing McH1-7, which they applied to various infected coral colonies using a targeted delivery method — covering them with plastic bags and injecting the solution, which allowed for maximum absorption.
Over a two-and-a-half-year period, the team monitored the health of the corals. Results were promising: all eight treated colonies displayed a significant reduction in disease spread, with deterioration limited to an average of only 7% of tissue compared to a worrying 30% in untreated counterparts. However, direct application of the paste to lesions resulted in no observable benefit, indicating that the method of treatment was crucial to its success.
Despite these encouraging results, Valerie Paul, a coauthor of the study, urged caution in proclaiming the probiotic as a comprehensive solution. She raised concerns about the practicality of the treatment approach, pointing out the logistical challenges of deploying plastic bags while underwater. Additionally, she highlighted the study’s limitation, noting that it only involved one species of coral despite the disease affecting over 30 species in total.
Nevertheless, Ushijima emphasized the study as a significant advancement in the realm of coral conservation, marking a proof of concept for the use of probiotics in the wild. With ongoing discussions about the potential benefits of coral probiotics surfacing for decades, this research opens the door for further exploration and could pave the way for novel strategies aimed at safeguarding coral ecosystems against formidable diseases in the future.
