Stony Coral Tissue Loss Disease (SCTLD) is a severe disease affecting corals. It was first noticed in 2014 around the Florida coast, and since then has spread to various other locations, especially in the Caribbean.

As the name suggests, it causes tissue loss in many corals. The mortality rate is estimated at between 60% and 100%. It appears that not all coral types are susceptible.

The causative agent is unknown, but is suspected to be an as-yet-unidentified microbe. There is some experimental data showing that colonies treated with antibiotics can recover (though of course this can't be done on any large scale). This strongly suggests a bacterial culprit, but a new (2021) study points instead towards a 'viral particle' as the damaging organism.

See : Frontiers in Marine Science, 05 November 2021.

Further info : Florida Keys National Marine Sanctuary