Times of the Islands Summer 2020

green pages newsletter of the department of environment & coastal resources
Coral bleaching
Coral bleaching events are also stressors that can cause
corals to die. Increased water temperatures and light
intensity can cause the system that turns that light into
energy to break down, leaving an overabundance of reactive
oxygen molecules, which damage the zooxanthellae
and the coral. The zooxanthellae that provide most of
the coral’s energy are expelled from the coral, leaving
behind a white tissue. If temperatures remain warm and
don’t give the zooxanthellae an opportunity to re-colonize
within the tissue, the corals are likely to die.
Ocean acidification
Ocean acidification is another very real threat for coral
reefs. As humans produce more and more carbon dioxide
as a byproduct of manufacturing, transportation, refrigeration
and cooling, oceans end up absorbing most of it.
When carbon dioxide and water mix, a series of chemical
reactions occur which result in the seawater becoming
more acidic. The problem is that many organisms in the
ocean, from corals to mollusks, rely on limestone, or calcium
carbonate, to build their skeletons or shells. This
increasingly acidic ocean water makes it that much more
difficult for these organisms to build their homes and
skeletons, and can even cause shells to dissolve!
Furthermore, different diseases have become more
prevalent within recent years; Stony Coral Tissue Loss
Disease is a very real, current threat to corals as it causes
the corals’ tissue to slough off of the skeleton.
PHIL DUSTAN
BEN FARMER
tions throughout the world increase demand for sources
of protein. For coastal communities, this often means
fishing to sustain their families, which leads to overfishing
if populations of fish species aren’t kept in check.
This particularly affects reefs when the herbivorous fish
numbers begin to drop. Without these fishes munching
on algae and controlling their levels, the algae begins to
grow unchecked. Furthermore, in the 1980s, a disease
affecting Diadema antillarum, or the long-spined sea
urchin, began to spread throughout the Caribbean, drastically
decreasing their numbers. Like herbivorous fishes,
these sea urchins also gnaw away at algae. Without these
grazers, algae then begin to smother corals, who need
sunlight to sustain themselves and grow. Without these
grazers, algae can also impede new corals from settling
on rocky areas.
Diadema antillarum, the long-spined sea urchin, was devastated by
a disease outbreak in the 1980s. They, like herbivorous fishes, gnaw
at algae.
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