GEOG 205 Ocean Acidification PDF

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Ocean Acidification Notes Reading Questions - Can you explain how increased CO2 concentrations in the atmosphere cause a decrease in ocean pH? - Can you list factors that increase the acidity of coastal waters relative to the open ocean -- and explain why? - Can you explain how acidification of coas...

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Ocean Acidification Notes Reading Questions - Can you explain how increased CO2 concentrations in the atmosphere cause a decrease in ocean pH? - Can you list factors that increase the acidity of coastal waters relative to the open ocean -- and explain why? - Can you explain how acidification of coastal waters is linked to eutrophication? - Can you explain how increased CO2 and acidity directly impact marine organisms? - Can you explain how increased CO2 and acidity indirectly impact marine organisms? Reading Notes - An increased uptake of atmospheric CO2 by the oceans has resulted in changes in seawater chemistry leading to ocean acidification - Ocean acidification begins when CO2 in the atmosphere dissolves in water to form weak carbonic acid. - Carbonic acid rapidly dissociates to produce bicarbonate ions. - Bicarbonate ions dissociate into carbonate ions - The dissolution of carbonic acid and bicarbonate releases protons into solutions and therefore lowers the pH (more acidic) - Summary of Ocean Acidification in Chemical Reactions - CO2 + H2O → H2CO3 - H2CO3 → HCO3- + H+  - HCO3 → CO3 - + H+ - The percentage dissociation is smaller in seawater than freshwater - Seawater has a natural capacity to buffer against changes in pH due to the natural presence of CO3- Buffering capacity of seawater will decrease as more CO2 is added and CO3- is consumed - Surface seawater pH is expected to continue to fall as atmospheric CO2 rises - Changed in oceanic pH may not be fully explained by increases in CO2 concentrations - SOx, NOx and eutrophication also contribute to increasingly acidic oceans - Eutrophication- process of nutrient over-enrichment of waters that can lead to hypoxia (oxygen depletion) and harmful algal blooms - Attributed to increased loadings from land based sources containing nitrogen and phosphorus (like sewage, chemical fertilizers) as well as micronutrients such as silica - Eutrophication can enhance ocean acidification - Excess organic matter production (e.g. algal blooms) in coastal and oceanic environments eventually undergoes microbial degradation, whereby O2 is consumed and CO2 is produced in the water column through microbial respiration → results in pH drop (more acidic) - Impacts of acidification - Hinders capacity to precipitate calcium carbonate minerals which marine organisms use to make their protective shells or skeletons - Existing structures vulnerable to dissolution

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Complexity of interactions - Biogeochemistry of coastal waters is complex with changes in carbonate chemistry providing either positive or negative feedback on increasing atmospheric CO2 by modifying the flux of Co2 between ocean and atmosphere What to do? - Nitrogen is the primary cause of eutrophication in many coastal ecosystems - Optimal management of coastal eutrophication suggests controlling both N and P in part because P can limit primary production in some systems - Possible Actions - International actions to mitigate CO2 emissions - Reduction in nutrient loading into coastal waters (control chemical fertilizer runoff and manage untreated sewage) - Research to understand the temperature-salinity-nutrient linkages - Improving developing countries capacity to monitor and create policies to reduce nutrient flow into the coastal waters from agriculture and non agricultural sources - Raise awareness regarding ocean acidification and eutrophication

Lecture Notes: Carbon Dioxide Variations - Relatively recent problem (since 1850) and the industrial revolution - Concentration of CO2 has significantly increased - The average CO2 concentration for February 2020 441 parts per million - The little inset shows an enlargement of the scale showing the dramatic rise in the CO2 concentration due to the industrial revolution Industrial Revolution - The invention of the steam engine which came around 1775 - Steam engine started the industrial revolution - Triggered the start of fossil fuels (i.e. coal, gas, and oil) - Many steam powered devices emerged at this sime - Steam engines were used all over the british empire Emissions of carbon dioxide exploded by modern technology starting with… 1. The steam engine 2. Electric motor 3. Gasoline engine 4. Vacuum tubes 5. Commercial aviation 6. Televisions 7. Nuclear energy 8. Microchip 9. WWW internet a. Google says it spends approximately 0.0003 kWh of energy on an average search query, translating to roughly 0.2 g of carbon dioxide. CO2 has been rising since the industrial revolution and continues to rise - Generally an upward trend

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The oceans have been moderating the CO2 emissions which has helped mitigate the effects The blue represents the ocean pH and shows the environmental cost - When CO2 increases, pH decreases making the ocean more acidic

Why does CO2 decrease the ocean pH? (Best explained from the reading) - An increased uptake of atmospheric CO2 by the oceans has resulted in changes in seawater chemistry leading to ocean acidification - Ocean acidification begins when CO2 in the atmosphere dissolves in water to form weak carbonic acid. - Carbonic acid rapidly dissociates to produce bicarbonate ions. - Bicarbonate ions dissociate into carbonate ions - The dissolution of carbonic acid and bicarbonate releases protons into solutions and therefore lowers the pH (more acidic) - Summary of Ocean Acidification in Chemical Reactions - CO2 + H2O → H2CO3 - H2CO3 → HCO3- + H+ HCO3- → CO3 - + H+ - The percentage dissociation is smaller in seawater than freshwater - Seawater has a natural capacity to buffer against changes in pH due to the natural presence of CO3- Buffering capacity of seawater will decrease as more CO2 is added and CO3- is consumed Saturation State - In the same waters where the carbon dioxide and pH were measured the saturation state (omega) i.e. the potential for the mineral to form or dissolve

Differences in Acidification of Coastal versus Open Ocean The following numbers can be mapped to the diagram on the right 1) There may be higher fallout of atmospheric compounds and acid rain that contribute directly to ocean acidification 2) 3, 4, & 5) Nutrients particularly nitrogen drains from fertilized watersheds and is released as point sources (e.g. discharges from sewage treatment plants) into rivers. This can result in eutrophication 5) Rivers carry carbonic acid that drains from solids in the watershed, the carbonic acid is formed during decomposition 6) Upwelling: occurs primarily occurs on west coasts, occurs as winds move surface waters away from the coast Eutrophication - Marine waters are nitrogen limited - Thus adding nitrogen simulate production of algae - Excess nitrogen means excess algae - Excess algae does not get consumed so it falls to the bottom as organic matter that microbes then eat. Microbes perspire CARBON DIOXIDE - THUS, more algae means more carbon dioxide

Upwelling

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Occurs on west coasts Occurs as winds move surface waters away from the coast Pale blue represents lower pH and generally the location of upwelling areas in this model-derived map of historical ocean pH in 1850

Differences in Acidification of Coastal versus Open Ocean - Most o four seafood comes from coastal waters, where wild populations are harvested and where it is grown through aquaculture operations that are now expensive around the world. Yet these waters are and will continue to be the most impacted Effects Of Increase Co2 And Ocean Acidification On Processes Of Different Groups Of Organisms RED = negative GREEN = positive White = no effect - Bottom images show cold and warm water coral - It both situations, ocean acidification has a negative impact on calcification

Effects of Increase Carbon Dioxide and Ocean Acidification on Finfish - Elevated carbon dioxide levels interfere with a major neurotransmitter, creating confused fish that will actually swim toward predators! - Otoliths- chunks of calcium carbonate in the inner ears of fish - They affect fish hearing and orientation - Problems with these will put a prey fish in danger and make a predator have trouble finding its prey Volcanic Underwater Vents - Provide a natural experiment to determine the impact of increased CO2 and acidification as the volcanic underwater vents are by nature more acidic and have increased concentrations of CO2 - Note in the graph below, there becomes a point where the pH decreases so much that sea urchins, limpets, and barnacles no longer exist

What does the loss of all these organisms mean? (Direct and Indirect Effects) - Sea creatures provide food and recreation to people - Impacts on commercial harvest and aquaculture of oysters all over the world- thus not just food, but income and livelihoods - Strong impact on regional economies - Think about possible causes of the megafaunal extinctions - Cascade effects - Loss of a predator or prey can affect each other’s population

Coral Reefs - More acid oceans means loss of corals - Corals are foundational species so loss of corals means loss of habitat for hundreds of species Many Relations and One Change Can Cause a Huge Disturbance...