Disease remains a major threat to the health of coral reefs.
For example, the recent outbreak of stony coral tissue loss disease, a distinct water-borne disease, is known to affect at least 20 species of stony coral.
The disease was first detected in Miami-Dade County in 2014, and since then it has spread throughout most of Florida’s coral reefs and into several countries and territories in the Caribbean.
Some of the northern reaches of the Florida reef lost as much as 60 percent of their living tissue area.
A new study by researchers at the Gulf Institute of Oceanography at Florida Atlantic University reveals how a common antibiotic used to treat bacterial infections in humans is treating disease-affected colonies of M. Cavernosa coral in situ.
M. cavernosa, also known as large star coral, is a species of hard or stony coral that is widely present throughout the tropical western Atlantic, including several areas currently affected by stony coral tissue loss disease.
Conservation of M. cavernosa is particularly important because of its high abundance and its role as a major reef-builder on the northern reaches of Florida’s coral reefs.
As part of the treatment, the researchers applied antibiotic treatment (a white paste) to the grooves surrounding the lesions at the edge of the coral colony.
The grooves are the white inner margin on the coral tissue, while the lesions are the pale/white tissue on the edge of the coral colony.
Chlorinated epoxy resin (a brown paste) was then applied to the channels created by the coral colonies and to compare the effects of the treatment on the lesions themselves.
A paper published in Scientific Reports experimentally evaluated the effectiveness of two interventions: chlorinated epoxy resin and amoxicillin in combination with Core Rx/Ocean Alchemists Base 2B, compared with an untreated control group.
The results showed that the BASE 2B plus amoxicillin treatment had a 95% success rate in curing individual disease lesions.
However, it does not necessarily prevent new lesions in treated corals over time.
There was no significant difference between the chlorinated epoxy treatment and the untreated control group, suggesting that chlorinated epoxy treatment is an ineffective intervention technique for tissue loss disease in stony corals.
The authors explain the new lesions in corals that had healed in the study.
It is possible that the pathogen responsible for stony coral tissue loss disease is still present in the environment and is re-infecting quieting stony corals.
It may also be that the duration and dose of this antibiotic intervention is sufficient to prevent stony coral tissue loss disease at the therapeutic focus, but not sufficient to eliminate its pathogen from other areas of the coral colony.
The study was conducted about 2 kilometers from the Lauderday Sea in Broward County, Florida, at a maximum depth of 10 meters.
Colony disease status and post-treatment lesion status were analyzed independently to assess the effectiveness of the treatment in preventing individual lesions, as well as to determine whether the treatment had any effect on the overall colony.
The coral colonies were monitored regularly over an 11-month period to assess the effectiveness of treatment by tracking the progression of lesions and overall disease status.