Ocean Acidification

Who cares about ocean acidification?

1. Marine microorganisms (corals, mollusks, crustaceans, sea urchins, and some algae) which build their calcareous shells or skeletons out of calcium carbonate– shell is (only) protection against predation

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2. Entire food chains (pelagic and coral reef ecosystems) and potentially fisheries (finfish and shellfish)

3. Climate (and us!): the biological, solubility and carbonate pumps

Ocean Acidification
A marine expression of CO2 pollution– a large level of misinformation since the research being done on this issue has largely taken place since 2004.
Main anthropogenic sources of CO2
Deforestation, burning of fossil fuels, cement making = > 440 billion tonnes of CO2
Emissions/year into oceans?
about 25%
Monaco Declaration
15- leading scientists from 26 countries and Prince Albert II of Monaco called for immediate action to reduce CO2 emissions to avoid severe damage to marine ecosystems from ocean acidification
What is pH?
pH is a measure of how acidic or basic a substance is, it stands for power of Hydrogen and is the negative log of the concentration of Hydrogen ions in a substance.
The Ocean Acidification Reaction

CO2+H2O<->H2CO2(carbonic acid)<->H++HCO2(bicarbonate ion)


This reaction increases acidity and lowers the availability of carbonate ions– reduction in carbonate ions is needed for calcification.

A form a calcium carbonate which is found in the shells of coccolithophores, foraminifera, echinoderns– relatively less soluble
A more soluble form of calcium carbonate, found in corals, mollusks, pteropods, some algae.
Solubility product constant of calcium carbonate
increases with decreasing temperature, and with increasing pressure, also increases with depth. the product of the two concentrations (saturated) — it’s a measure of how much can “fit” into solution. older water have higher solubility product constant because they have more respiration– more carbon
Saturation State
Most waters are not at equilibrium with respect to either calcite or aragonite. The saturation state reflects this, it is given by the observed concentration of teh carbonate ion over the concentration of the carbonate ion that “fits” i.e. the saturation concentration. If the saturation state is over 1, we are in a state of supersaturation and it will precipitate. If less thant 1, understaturation, more will dissolve
Saturation Horizon
transition depth between the supersaturated upper ocean and the undersaturated deep ocean, when saturation state equals 1
Calcite/Aragonite Compensation Depths
Depths below which the rate of supply of calcite/aragonite is equal to the dissolution rates, such that no calcite/aragonite is preserved
Depth at which dissolution of calcite increases dramatically
Le Chatelier’s principle
A chemical system at equilibrium which experiences a change in concentration will experience an equilibrium shift to counteract the change and a new equilibrium will be established. In the case of ocean acidification, increasing carbon dioxide increases the dissolution of calcium carbonate
Things we don’t know
Sound propagation and olfactory cues (effects on), the biological response of organisms to known acidification is still new to study and therefore unclear