LectureOcean Acidification

What is Ocean Acidification?

• Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units. Moving the ocean's pH from 8.179 to a current pH of 8.069, which means the ocean is about 30% more acidic now than it was in 1751 (SCOR 2009). Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30 percent increase in acidity.

http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

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Acidity and Alkalinity

• Acid releases a hydrogen ion (H+) when dissolved in water.• Alkaline (or base) releases a hydroxide ion (OH-) in water.

Acidity is commonly measured using the pH scale. Pure water has a pH of about 7, which is considered neutral. A substance with a pH less than 7 is considered to be acidic, while a substance with a pH greater than 7 is considered to be basic or alkaline. The lower the pH, the more acidic the substance. Like the well-known Richter scale for measuring earthquakes, the pH scale is based on powers of 10, which means a substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4. For more

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pH Scale• Measures hydrogen ion concentration

• Low pH value, acid• High pH value, alkaline (basic)• pH 7 = neutral

• Pure water

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Carbonate Buffering System• Ocean pH averages 8.1 and ranges from 8.0 to 8.3.• Buffering keeps the ocean from becoming too acidic or too basic.

• Precipitation or dissolution of calcium carbonate, CaCO3, buffers ocean pH.

• Oceans can absorb CO2 from the atmosphere without much change in pH.

Fig. 6-17

Ocean Acidification

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• The extent of floating sea ice in the Arctic Ocean, as measured at its annual minimum in September, showed a steady decline between 1980 and 2009.Source: National Snow and Ice Data Center, graph compiled by Secretariat of the Convention on Biological Diversity (2010) Global Biodiversity Outlook 3, May 2010

http://www.globalissues.org/article/172/climate-change-affects-biodiversity

http://gbo3.cbd.int/

• Source: John Bruno, It’s not climate change, it’s ocean change!, Climate Shifts, July 12, 2010

• The implications of this is further explained with Inter Press Service’s freezer analogy: The world’s northern freezer is on rapid defrost as large volumes of warm water are pouring into the Arctic Ocean, speeding the melt of sea ice.

http://www.climateshifts.org/?p=5585http://www.ipsnews.net/news.asp?idnews=54278

Climate change: Ocean acidification amplifies global warming

• Observations of reduced DMS concentration with decreasing seawater pH from different mesocosmexperiments.

https://www.sciencedaily.com/releases/2013/08/130826095846.htmKatharina D. Six, Silvia Kloster, Tatiana Ilyina, Stephen D. Archer, Kai Zhang, Ernst Maier-Reimer. Global warming amplified by reduced sulphur fluxes as a result of ocean

https://www.sciencedaily.com/releases/2013/08/130826095846.htm

• the relationship between changes in ocean carbon dioxide levels (measured in the left column as a partial pressure and acidity (measured as pH in the right column).

https://www.epa.gov/climate-indicators/climate-change-indicators-ocean-acidity

Between the 1880s and the most recent decade (2006–2015).

A negative change represents a decrease in saturation

The lower the saturation level, the more difficult it is for organisms to build and maintain their skeletons and shells..

Data source: Woods Hole Oceanographic Institution, 2016

• Carbon dioxide levels have risen in response to increased carbon dioxide in the atmosphere, leading to an increase in acidity (that is, a decrease in pH) (see Figure 1).

• Since the 1880s, increased carbon dioxide has led to lower aragonite saturation levels in the oceans around the world, which makes it more difficult for certain organisms to build and maintain their skeletons and shells (see Figure 2).

• The largest decreases in aragonite saturation have occurred in tropical waters (see Figure 2); however, decreases in cold areas may be of greater concern because colder waters typically have lower aragonite saturation levels to begin with.

Biological Impacts

• Dramatic effect on some calcifying species, including oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton

Pteropod Limacina Helicina. Courtesy of Russ Hopcroft, UAF.

National Geographic Images.

The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon.

http://ngm.nationalgeographic.com/2007/11/marine-miniatures/acid-threat-text

future atmospheric carbon dioxide will be high enough to lower ocean surface pH to 7.8 by the year 2100 (Royal Society 2008). laboratory studies suggest a pH about this low could dissolve coral skeletons and may cause reefs to fall apart (Fine and Tchernov 2006).

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Coral Reefs in Decline

• 30% healthy today, 41% healthy in 2000• One third of corals – high risk of extinction• Humans – greatest threat• Other threats

• Hurricanes• Global warming

• Coral bleaching• Floods• Tsunami

Coral bleaching

• Coral bleaching occurs when symbiotic zoothanthellae algae is removed or expelled

• Associated with high water temperatures

Figure 15B

Lecture�Ocean AcidificationWhat is Ocean Acidification?Acidity and Alkalinity슬라이드 번호 4pH ScaleCarbonate Buffering System슬라이드 번호 7Ocean Acidification슬라이드 번호 9슬라이드 번호 10슬라이드 번호 11Climate change: Ocean acidification amplifies global warming슬라이드 번호 13슬라이드 번호 14슬라이드 번호 15Biological Impacts슬라이드 번호 17슬라이드 번호 18슬라이드 번호 19Coral Reefs in DeclineCoral bleaching슬라이드 번호 22