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Ocean Acidification: Net Ecosystem Calcification Response to an Elevated pCO2 Level

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Title:Ocean Acidification: Net Ecosystem Calcification Response to an Elevated pCO2 Level
Authors:Tan, Adrian
Contributors:Mackenzie, Fred (advisor)
Oceanography (department)
Global Environmental Science (department)
Keywords:fossil fuel
ocean acidification
Date Issued:2007
Publisher:University of Hawaiʻi at Mānoa
Place of Publication:Honolulu
Abstract:Ocean acidification is the lowering of seawater pH due to increased pCO2 levels
in the atmosphere brought about by human activities of fossil fuel burning and
deforestation. As of 2005 atmospheric pCO2 levels had reached 380 ppm (IPCC, 2007),
the highest level for the last 640,000 years (Petit et al.,1999; Barnola et al.,2003,
Siegenthaler et al., 2005, IPCC, 2007). The increase in pCO2 in the atmosphere is an
immediate concern because of its direct relationship with ocean chemistry. The change
in ocean chemistry due to the addition of CO2 lowers both the pH and saturation state
of seawater with respect to different CaCO3 minerals (Andersson et al., 2003, Morse et
al., 2006). Calcification rates decrease as the saturation state of seawater with respect to
CaCO3 decreases, hence producing weaker skeletons for calcareous organisms. The
weaker coralline structures lead to greater vulnerability to physical and biological
A diurnal study of the effects of increased pCO2 levels in the atmosphere on
calcification rates of corals was done using a flow through mesocosm in which the
coral Montipora capitata was grown. The experiment quantitatively compared the
calcification rates of corals in tanks with an elevated CO2 level of 700 ppm (projected
atmospheric CO2 level by the year 2100) to those of tanks with ambient CO2 levels
(380 ppm). Net ecosystem calcification (NEC) rates were calculated using total
alkalinity (TA) and pH measurements of water flowing in and out of the tanks. The
results of this experiment showed that an elevated CO2 level of ~700 ppm induced a
significant reduction in net calcification rates compared to NEC in the tanks with
ambient CO2 levels. The calculations of NEC showed average net dissolution rates over
a diurnal cycle for tanks with elevated CO2 levels.
Pages/Duration:56 pages
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Rights Holder:Tan, Adrian
Appears in Collections: Global Environmental Science Theses

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