Impacts of Global Warming on
the Ocean and Coral Reefs
Emily Underriner
ChE 359
November 24, 2008
Agenda
• Global Warming and Climate Change
• The Ocean and Coral Reefs
• Impacts
• Temperature
• Acidity
• The Future Challenges
Global Warming
• Prior to industrial
revolution: 280 ppm
• Current day: 387 ppm
• “Greenhouse” effect
• By 2100, CO2 levels to
double pre-industrial
revolution
• Loss of environmental
biodiversity, disrupt
ecosystem processes, and
reduce ecological goods
and services
Importance of the Ocean
• Yearly global economic value of $21 trillion
• The largest sink/reservoir of atmospheric CO2
emissions
– Contains 50 times the amount of carbon in the
atmosphere and 10 times more carbon than is
held by soil and plants
• CO2 uptake has not been without negative
consequences
Coral Reefs
• Coral reefs: corals, coralline algae, fish, others
• Corals: small animals
– Begin as larva, attach to hard surface
– Build coral skeleton via reaction of Ca and CO2 to make
CaCO3, or limestone
• Symbiotic relationship with yellow-brown algae,
zooxanthellae
– Provide coral with nutrients
– Coral provides protection and
access to light
http://oceanworld.tamu.edu/students/coral/coral5.htm
Coral Reefs
Source: wwf.org
Source: myclimatechange.net
Importance of Coral Reefs
• Among the most diverse and productive ecosystems
on earth (tropical rainforests of the sea)
• Support 25% of all known aquatic wildlife species,
over 4,000 species of fish, 700 species of coral, and
thousands of others
• Provide: food, supply economic income via fishing
and tourism, shoreline protection, integral ocean
sink for atmospheric carbon dioxide
• Supply $375 billion in ecosystem goods and services
to the global economy each year
Impacts on the Ocean
• Temperature Rise
– Air has higher thermal heat capacity than water
– Since the 1950s, average temperature increase of
0.31 °C in top 300 meters of water
• Acidification
– Since the 1900s, 30% increase in H+ in ocean
Temperature Impact on Coral Reefs
• Coral reefs very sensitive to changes in the
ocean’s temperature
– Generally require T between 25°C and 29°C
• T change of only a few degrees above the
long-term average can cause coral to die
– “Bleaching” – loss of zooxanthellae
• Over 60% of the earth’s coral reefs will be lost
by the next 25 years
Coral Reef Bleaching
• Between 1979 and 1990, out of 105 mass coral
moralities, 60 coral reef bleaching events were
reported, compared with only three bleaching events
among 63 mass coral moralities for the preceding
103 years
Source: Texas A&M University, Coral Reefs
Source: http://www.marinebiology.org/coralbleaching.htm
Acidification
• Increasing ocean CO2 concentration
• Historically: pH of 8.2
• Since early 1900s, pH drop by 0.1 units, estimate a
drop in seawater pH by 0.5 units by 2100
• CO2 reacts with water to form carbonic acid (H2CO3)
– Increases carbonate (HCO3−) and H+ in the ocean surface
water (reducing pH), decreases bicarbonate (CO32−)
• Coral reef organisms rely on the concentration of
bicarbonate to form hard skeletons
• Predict threshold to be met around 2050
The Future
• More research on coral reef impacts
• Increasing carbon concentration is dangerous
• GHG and carbon mitigation
– Reduce emissions
– Sequestration
• Impacts on entire ocean ecosystem difficult to
predict
Thank you!