Impacts of Global Warming on the Ocean and Coral Reefs

Emily UnderrinerChE 359

November 24, 2008

Agenda

• Global Warming and Climate Change• The Ocean and Coral Reefs• Impacts

• Temperature• Acidity

• The Future Challenges

• 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

Global Warming

• 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

Importance of the Ocean

• 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

Coral Reefs

http://oceanworld.tamu.edu/students/coral/coral5.htm

Source: myclimatechange.net

Source: wwf.org

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

Importance of Coral Reefs

• 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

Impacts on the Ocean

• 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

Temperature Impact on Coral Reefs

• 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: http://www.marinebiology.org/coralbleaching.htmSource: Texas A&M University, Coral Reefs

Coral Reef Bleaching

• 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

Acidification

• 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

The Future

Thank you!