A disease which has devastated one type
of Caribbean coral, Elkhorn coral, has been traced back to
bacteria found in human faeces. On some reefs, 95% of
Elkhorn corals, which used to be the commonest coral in the
Caribbean, have been wiped out by the condition, called
white pox that shows itself as white spots on the coral,
which spread and kill the coral, destroying the living
tissue. On average, the disease spreads at a rate of 2.5
square centimetres of coral a day.

The problem is particularly bad in the
Florida Keys, where human waste is treated in septic fields
rather than extensively treated to kill bacteria.  It
is thought to be the first time that a human gut bacterium
has been linked to coral disease.