Deadly stony coral disease reaches Little Cayman

Marine researchers have confirmed the first cases of stony coral tissue loss disease on Little Cayman, after finding lesions on corals over a mile-long stretch of reef near the island.

The disease, known as SCTLD, decimated populations of stony coral species on Grand Cayman’s reefs after it was first found there in 2020, but the Sister Islands had escaped the onslaught until now.

The Department of Environment, on 4 Sept., reported it had confirmed that lesions, which had been spotted on corals at Black Hole and Windsock Reef dive sites on the southwest coastline of Little Cayman, were caused by stony coral tissue loss disease.

Based on data on the progress of the disease on Grand Cayman, researchers have determined it spreads at about one mile a month, meaning the infection likely became established in Little Cayman in July this year, the DoE reported.

So far, there have been no reports of the disease being found on Cayman Brac.

In Grand Cayman, the Department of Environment’s staff and volunteers had battled to stop or slow down the unrelenting march of the disease by using antibiotic paste on infected corals, but it spread around the entire island within 18 months, after being first found at the Penny’s Arch site off Rum Point in June 2020.

The disease was first identified off the coast of Miami-Dade County in Florida in 2014, and since then, it has spread throughout the Caribbean.

Efforts to try to stop the disease from reaching Little Cayman, an internationally renowned dive destination, had included instructing divers to disinfect their dive equipment and boaters to add bleach to their bilge water prior to arriving on the island.

“These measures successfully delayed the transmission of [the disease] from Grand to Little Cayman for the last several years and are still recommended for travel to Little Cayman so as not to add any additional infection sites to the reefs there,” the Department of Environment said.

It added, “Unfortunately, data collected in Grand Cayman has proven that once established, the spread of SCTLD is essentially unstoppable. However, with continued vigilance in keeping dive gear and bilge water island specific, perhaps we can delay the spread of SCTLD to Cayman Brac for a few more years.”

The department said its scientists and senior management would continue to monitor the spread of the infection in Little Cayman and “are evaluating various new and old methods to mitigate and manage the disease”.

Disease adding pressure to already-stressed reef

The discovery of SCTLD on Little Cayman will put additional stress on a reef already reeling from the impacts of bleaching.

In 2023, before a major worldwide bleaching event, surveys by the Little Cayman-based Central Caribbean Marine Institute recorded that the average coral cover in Little Cayman had been at its highest since monitoring began in 1999, at 27.3%. Following the severe bleaching, the institute found that coral cover in 2024 plummeted to the lowest ever recorded – just 10%.

A Health Reef Report Card produced by the institute noted that between June 2023 and August 2024, the coral health state on the island had changed substantially, pointing out that in 2023, over 90% of reefs were recorded to be in good to very good condition, but by the following year, 0% of the reef was recorded as being in a better-than-good condition.