More stony coral disease found at dive sites

Latest infection site found off Smith Cove

Stony coral tissue loss disease impacts 25 species of hard corals, which form a major part of coral reefs. - Photo: Drew McArthur

A change in the progression rate of stony coral tissue loss disease has led the Department of Environment to suspect divers and boat operators may be spreading it.

During an update on the disease with watersports operators at the Government Administration Building on Wednesday, 26 May, DoE research officer Tammi Warrender said the latest data gathered off Grand Cayman’s eastern coast showed gaps between the infected sites that span approximately two miles in some areas.

Additionally, an isolated area containing the disease has been spotted at Armchair Reef off Smith Cove, along the southwestern coast, which created a third front for the research officers to tackle.

“What this means is now that [stony coral tissue loss disease] is there, it will start to spread northward and eastward,” said Warrender. “So, this makes it a lot harder for us to do our intervention efforts.”

Scientists are still not exactly sure how SCTLD spreads. Originally, it was thought that it moved from reef to reef via sea currents and, at times, with the assistance of unwitting divers and boat operators via contaminated gear or the release of bilge water.

DoE Deputy Director Tim Austin, speaking at a Cayman Islands Tourism Association meeting on Thursday, 27 May, said the discovery of the disease at individual dive sites not directly connected to the original line of infection found along the north coast last year has led to a “real horrible inkling this might be related to diving practices”.

The red areas on the map show where stony coral tissue loss disease has been found, as of 5 May. The Armchair Reef dive site, off Smith Cove, can be seen in the southwestern corner of the island. – Map: DoE

For the past 10 months, the DoE has been battling SCTLD along Grand Cayman’s northern coast. The highly infectious, coral-killing disease was first spotted locally in June 2020 at Penny’s Arch, near Rum Point, and has since spread along the northern coast to the western and eastern tips of the island.

Warrender said when Penny’s Arch was initially surveyed last June, officers found approximately 10% of the coral had died, 35% was unhealthy, and 55% was healthy. By April 2021, 57% of the hard coral at Penny’s Arch had been lost.

“This just shows you the loss of hard coral cover that we might experience around the island,” she said. “This is what we are experiencing at the epicentre of Penny’s Arch. It’s still progressing through that area so it might be higher by the time the disease passes through.”

New guidelines

In light of the spread, the DoE issued disinfection guidelines for local divers.

It has now proposed additional guidelines for divers and tour operators to follow, in an attempt to stem the progress of the disease.

These tips include renting local dive gear when diving in Cayman Brac or Little Cayman, as so far no sign of the disease has been found on the Sister Islands. And if divers must travel with their own gear, the DoE suggests that the equipment is thoroughly disinfected prior to travelling to the Sister Islands.

The DoE is also calling on divers and operators who are on multi-site dive trips to refrain from leaving an infected site and then visiting a healthy area; instead, they should stay in the same geographical location.

  • Additional reporting by Cayman Compass journalist Norma Connolly

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  1. This looks as if led by currents, same basic stuff I looked at off VIRGIN GORDA BVI,there was an area, off the beaten path, NOBODY SWAM THEREnor did ANYONE DIVE THERE, just been curious, and was there , so every time visited in over a 10 year time frame, was UNABLE to have figured it out, even the resort had asked me what & why I was there? Right up to resort, I had also noticed like an GREEN Floating below surface , like an algae, when I started there in 85 no such stuff was there, all the way up to the mangroves there, but NOBODY knew what caused it, it’s NOT from agricultural runoff, as there in none ! BTW, for some years now the GREAT BARRIER REEF, has ALSO had hard coral die off , but had no answers either.

  2. This disease in my opinion is a bigger threat to the Cayman Islands than Covid-19. DOE has made recommendations concerning using dive gear in the Sister Islands, but has any thought been given to some of the dive operations bringing dive boats / divers for day trips to the Sister Islands?