Threats to Corals
RISING OCEAN TEMPERATURE
Corals are sensitive to changes in
temperature, and an increase of just
two degrees Celsius over a few weeks
to months can be enough to cause
catastrophic coral bleaching. When corals
are stressed from the warmer water, they
expel their photosynthetic zooxanthellae
algae which are critical to their survival.
Once the zooxanthellae algae leaves,
the corals turn a ghostly white colour and
it is difficult for them to survive. When
corals are bleached, harmful algae taking
over the corals. And with the loss of
herbivorous fish, these algae can quickly
out-compete and kill the coral.COASTAL DEVELOPMENT
Coastal development is one of the biggest threats to coral reefs. This
includes construction of hotels, resorts, and homes along the coastline,
as well inland mining and logging, especially on smaller islands. This
development often stirs up sediments which cover and kill corals. In the
case of inland activities, once trees are removed, sediments can easily enter
the ocean after rainfall. During mining activities, sediments and harmful
chemicals can enter the ocean through freshwater streams or runoff.MARINE DEBRIS
Plastics and other marine debris are
becoming an all too familiar sight. Plastics
which enter the ocean are eaten by fish
and other marine life, or worse, they break
apart into millions of microscopic pieces
that absorb chemicals from the water
before they are eaten. Larger debris like
nets, plastic bags and fabrics can also
become tangled around corals, causing the
coral tissue to die. It is estimated that more
than 250 million tons of plastics will have
made their way into our ocean by 2025.of plastics will have
made their way into our
ocean by 2025zooxanthellaeOCEAN ACIDIFICATION
Increased carbon dioxide (CO 2 ) in the
atmosphere eventually makes its way into
the ocean. As this CO 2 is absorbed, the pH
of the ocean drops, resulting in a more
acidic environment. Normal seawater
is between 7.5 and 8.5 pH and anything
below 7 is considered acidic. Corals use
calcium carbonate to build their solid
skeletons, but in an acidic ocean, this
skeleton becomes weaker and corals have
more difficulty building their skeleton.
While this is not such a concern for
mature colonies, ocean acidification may
be affecting the growth and development
rates of baby corals, causing deformities
in their skeletons.CO 2
H 2 CO 3
H 2 O
250
MILLION TONS