Gases in Seawater

These flashcards cover essential concepts about gases in seawater, including their composition, behavior, and the biochemical implications for marine life.

What atmospheric gases are dissolved in seawater?

Various atmospheric gases, including CO2.

What factors determine the solubility of gases in seawater?

Temperature, salinity, pressure, and pH.

What is the primary form in which CO2 is found in seawater?

90% of CO2 is present as bicarbonate ions (HCO3−).

What is DIC in the context of seawater?

DIC stands for Dissolved Inorganic Carbon, which includes HCO3−, CO32−, and CO2(aq).

Where is CO2 (aq) lower in the ocean?

In the euphotic zone.

How does the level of CO2 in seawater act as a buffer?

It resists changes in pH.

What happens to seawater CO2 levels with higher atmospheric CO2?

More CO2 is absorbed, shifting seawater equilibrium and decreasing pH.

What are the impacts of increased CO2 levels in seawater?

Reduced calcification rates, increased dissolution rates, decreased muscle mass, and reduced fertilization success.

What is the compensation depth in the ocean?

The depth where O2 consumed by respiration equals that released by photosynthesis.

What is an Oxygen Minimum Zone (OMZ)?

Areas very low in O2 caused by respiration of organisms and lack of O2 replenishment.

What factors contribute to the expansion of OMZs due to climate change?

Warmer oceans hold less O2, increased stratification, and reduced Deep Water Mass formation.

How does oxygen solubility relate to temperature?

Higher temperatures lower oxygen solubility in water.

What sediment characteristics affect O2 concentration?

Well sorted sediments have high porosity and permeability; poorly sorted have low porosity and permeability.

What gases, other than CO2, are found in seawater?

Nitrogen (N2), Sulphur dioxide (SO2), Nitrous oxide (N2O), Carbon monoxide (CO), Methane (CH4), Methyl iodide (CH3I), Dimethyl sulphide (DMS).

What are the three chemical species that constitute Dissolved Inorganic Carbon (DIC)?

Aqueous carbon dioxide (CO{2(aq)}), bicarbonate (HCO{3}^{-}), and carbonate ions (CO_{3}^{2-}).

How does the dissolution of CO_{2} in seawater affect the concentration of hydrogen ions (H^{+})?

It increases the concentration of H^{+} ions, which directly leads to a decrease in pH (ocean acidification).

What is the specific chemical reaction for the buffering of seawater using carbonate ions?

CO{2} + H{2}O + CO{3}^{2-} ightarrow 2HCO{3}^{-}

Why is the biological pump significant for CO_{2(aq)} levels in the euphotic zone?

Phytoplankton utilize CO_{2} for photosynthesis, lowering its concentration in surface waters and facilitating more absorption from the atmosphere.

What is the relationship between the Saturation State (\Omega) and calcification?

When \Omega > 1, conditions favor the formation of shells; when \Omega < 1, seawater is corrosive and calcium carbonate (CaCO_{3}) dissolves.

How does ocean stratification impact the replenishment of Oxygen (O_{2})?

Stratification creates density barriers that prevent the vertical mixing of oxygen-rich surface water into the interior ocean.

In Oxygen Minimum Zones (OMZs), why does oxygen depletion occur at mid-depths?

Due to high rates of microbial respiration breaking down sinking organic matter, combined with slow water renewal.

What is the difference between sediment Porosity and Permeability?

Porosity is the total volume of pore space available for gas/water, while permeability is the measure of how easily those fluids can flow through the sediment.

What is the climate significance of Dimethyl sulphide (DMS) released by the ocean?

It acts as a precursor for sulfate aerosols, which serve as cloud condensation nuclei and influence global cooling.

How does Salinity specifically affect gas solubility in seawater?

As salinity increases, gas solubility decreases because the salts compete for water molecules, a process known as the 'salting out' effect.