Ocean Acidification

è Ocean Acidification is the decrease in pH that is occurring due to the absorption of CO₂ from the atmosphere.

è Carbon in living organisms can be stored after the organism dies. If it is buried under layers of mud and sand, it can slowly decompose over millions of years and form fossil fuels such as coal and oil.

è When fuels are burned à CO₂ released into the atmosphere.

è Huge increase in burning fossil fuels has significantly increased CO₂ levels in the atmosphere.

Coral Bleaching:

è CO₂ can trap heat in the atmosphere, which can raise the surface temp. of oceans.

è Coral exists in a symbiotic relationship with a type of algae called zooxanthellae, which produces sugars for the coral via photosynthesis. In return the algae get a safe habitat and nutrients from the algae.

è Increased Ocean temp. à algae separate from coral à coral loses colour and goes white (calcium carbonate skeleton exposed). Also loses primary food source.

CO₂ in the Ocean:

è 30% of CO₂ ends up in the ocean.

è CO₂ (soluble in water) à equilibrium producing carbonic acid:

è CO₂ (aq) + H₂O (l) ⇌ H₂CO₃ (aq)

è H₂CO₃ is a weak diprotic acid à causes following equilibria:

è H₂CO₃ (aq) ⇌ HCO₃^- (aq) + H⁺ (aq) K = 2.5 X 10^-4

è HCO₃^- (aq) ⇌ CO₃^2- (aq) + H⁺ (aq) K = 4.7 X 10^-11

è Increased [CO₂] shifts equilibrium to the right à increased [H₂CO₃] in ocean à caused equation to shift to the right à increased [H⁺] à lower the pH of ocean.

è Avg. pH of ocean = 8.1 à expected to drop to 7.8 if CO₂ emissions continue (100 years) à affect marine life which are very sensitive to changing oceans conditions.

Calcification:

è Marine animals with shells rely on precipitate reaction between calcium and carbonate ions to form calcium carbonate shells.

è Increased acidification can shift this equilibrium to the left:

è HCO₃ (aq) ⇌ CO₃^2- (aq) + H⁺ (aq)  K = 4.7 X 10^-11 (low = already favours the reverse reaction)

è Increase in [H⁺] will force the equilibrium above to reduce [H⁺] à shifts to the left, decrease [CO₃^2-] in ocean.

è Reduces availability of carbonate ions for marine shells, shifting this equilibrium left:

è Ca²⁺ (aq) + CO₃^2- (aq) ⇌ CaCO₃ (s)

è Makes it harder to carbonate ions that they (marine life) need. Threaten the lives of the marine life that rely on shells.

è Since carbonates react with acids, increasing ocean acidity can lead to dissolving shells and other marine creatures.

è 2H⁺ (aq) + CaCO₃ (s) à Ca²⁺ (aq) + CO₂ (g) + H₂O (l)

è Weakens shells and hinders survival.

è Reduced calcification à destruction of species à effect overall food chain. This disruption in the food chain can lead to decreased fish populations, ultimately impacting commercial fisheries and local economies that rely on these resources.

Furthermore, the decline in fish populations can also affect the livelihoods of communities dependent on fishing, leading to economic instability and reduced food security.

Photosynthesis - takes CO2 from the atmosphere and uses it to make glucose, which acts as an energy source. EQUATION: 6CO2 (g) + 6H2O (l) + ENERGY —> C6H12O6 (aq) + 6O2 (g).

This is an endothermic reaction and can only occur in presence of sunlight and chlorophyll.

Respiration - Exothermic (reverse of photosynthesis)

Enhanced Greenhouse Effect - the process by which certain gases in the Earth's atmosphere trap heat, leading to an increase in global temperatures. This phenomenon is primarily caused by the accumulation of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) due to human activities such as fossil fuel combustion, deforestation, and industrial processes.

CO2 —> more soluble in cold water.

Champayne Sites - Large amounts of CO2 escape from undersea volcanoes. Researchers gain insight into the effects of future increase in CO2. Can see which plants + marine life adapt to lower pH and which cannot survive at all —> in liquid state (CO2).

Decalcification - H+ (aq) + CO3^-2 (aq) —> HCO3- (aq) » Additional H+ reacts with CO3^-2, which lowers its concentration in oceans. Formation of CaCO3 structures is more difficult for marine life. Lowered pH —> rate and amount of calcification to drop.