Rebecca Cebulka
What are Corals?
 Marine invertebrates that live in colonies
 Similar to anemones
 Some can catch small fish and plankton
 Typically live in deep ocean
 Most obtain nutrients from symbiotic algae which live
in the coral’s tissues
 Grow in clear, shallow water
 Form coral reefs
Coral Reefs
What is coral bleaching?
 Corals get their color from symbiotic algae
 Changes in surrounding water cause stress
 Warmer or colder temperatures
 More or less light
 Stress causes coral to expel algae, leading to bleaching
and a lack of food for the coral
CHANGES IN
WATER
CORAL BECOMES
STRESSED
COLOR-PRODUCING
ALGAE EXPELLED
Healthy Coral & Bleached Coral
What Causes Bleaching?
 Temperature changes of 1-2°C over several weeks
 Increase in T more likely to cause bleaching
What Causes Bleaching?
 Solar Radiation
 Increased UV
radiation(280-400nm)
and photosynthetically
active radiation (400700nm)
 Corals in shallow waters
are more prone to
bleaching – coral reefs
especially!
Effects of Coral Bleaching
 Algae provide necessary nutrients for corals –
prolonged bleaching will result in coral death due to
lack of food
 Destroy ecosystems which are the only home to many
species used for both food and medicine
Effects of Coral Bleaching
 Destroy reefs that protect shores from the impact of
waves and storms
 Cut back on economic benefits to local communities
from tourism
 Becoming more and more prevalent
Other Dangers
 Increased carbon dioxide
 Raises ocean acidity, preventing coral from building its
calcium carbonate skeleton
 Won’t kill coral directly, but makes it more difficult to
recover from things such as bleaching
Other Dangers
 Overfishing
 Kills off a main
part of the
reef’s
ecosystem
 Some types of
fishing
involves
scraping the
ocean floor,
ripping up
coral
In Summary
 Coral bleaching occurs when corals expel symbiotic
algae due to changes in the surrounding water
 Causes of coral bleaching include increasing water
temperature and solar radiation
 Increased CO2 in the air is making it difficult for coral
to recover from bleaching events.
 Death of coral reefs is becoming more and more
common and is expected to continue.
References
 http://ocean.si.edu/corals-and-coral-reefs
 http://www.marinebiology.org/coralbleaching.htm
 http://oceanservice.noaa.gov/facts/coral_bleach.html
 http://www.onr.navy.mil/focus/ocean/habitats/coral2.
htm
 http://www.globalissues.org/article/173/coral-reefs