Seawater Composition IV: Gases in the ocean

What are the most abundant gases in the atmosphere? In the ocean?

atmosphere: Nitrogen & Oxygen ocean: Nitrogen, oxygen and carbon dioxide

What is meant by saturation concentration? What factors do saturation concentrations depend on?

The maximum amount of a gas that water can hold at a given temperature and salinity. Temperature, salinity, and pressure

What is meant by atmospheric equilibrium? Is the ocean surface always in equilibrium? Why or why not?

When gas exchange makes ocean surface gas levels match atmospheric levels. No; biology, mixing, and temperature changes disrupt equilibrium

What are the physical and biological factors that impact gas saturation in the ocean?

Temperature, mixing, photosynthesis, respiration, and air–sea exchange

What factors impact the O2 and CO2 profiles in the ocean?

O2: Photosynthesis at the surface and respiration/remineralization at depth

CO2: Respiration at depth and air–sea exchange at the surface

What is pH? What is meant by basic and acidic?

A measure of hydrogen ion concentration. Acidic has more hydrogen ions; basic has fewer

Why is seawater pH relatively constant? What is meant by “buffering capacity”? Be able to describe what

happens (in terms of carbon species) if acid is introduced into the ocean.

The carbonate system buffers changes by shifting among CO2, bicarbonate, and carbonate.

Carbonate converts to bicarbonate, reducing pH change

What processes influence the concentration of CO2 in surface waters?

Air–sea exchange, photosynthesis, respiration, and temperature

What impact does increasing anthropogenic atmospheric CO2 have on ocean chemistry and carbonate

organisms in the ocean?

Increases acidity and reduces carbonate availability for shell‑forming organisms