Coral reefs are in danger (non-human factors)
The greatest global threats to coral reefs are the increased ocean
temperatures and changing ocean chemistry because of increasing
levels of carbon dioxide in seawater.
Warming temperature causes thermal stress to corals. They lose their
symbiotic algae – living in their tissue – that produce food for their host,
placing big stress on the coral polyps. Without this algae, corals lose their
„normal” yellowish-brown colouration and they turn white, which is the colour of
their skeleton. Coral colonies can die or be more vulnerable to other threats
such as infectious disease if the bleaching is severe.
Ocean acidification is a change in ocean chemistry in response to the
uptake of carbon dioxide from the atmosphere. Because atmospheric
concentrations of CO2 increase so do oceanic concentrations.
Carbon dioxide entering seawater reacts to form carbonic acid, causing
an increase in acidity and this compound reduces coral growth.
Also, sea level rise increased the frequency and intensity of tropical storms,
and altered ocean circulation patterns can also affect or destroy coral
reefs. Strong storms can break the corals themselves but they can cause
sedimentation. As sediment deposits onto reefs can decrease with their
ability to feed, grow, and reproduce.