Chemistry of seawater Salt pH Gases Nutrients

How did the ocean become salty?

How did the ocean become salty? Salt is metals from Earth’s interior. It is added by Volcanic gases Fluids from vents River outflow Dusts from land

Salinity Salinity: the concentration of salt in a solution Salinity of the oceans has remained fairly constant over the last 1.5 billion years

For salinity to remain constant, there are ways salts are added and removed

How the ocean became salty There are also sources that remove salt from the ocean sea spray biological processes adsorption and precipitation

What is in sea water? What is in salt? the taste test

Salinity of surface seawater What do you notice?

What do you notice?

Salinity in the ocean varies across the surface of the ocean and with depth

Salinity in the ocean is variable Brine pools have water that is 4-5X denser than the surrounding ocean water and act like lakes at the bottom of the ocean oceanexplorer.noaa.gov

How does salt affect aquatic organisms? Driving force of ocean currents (we’ll learn more later) Affects osmoregulation Maintenance of the internal balance of water and dissolved solids

Chemistry of seawater Salt pH Gases Nutrients

What do you notice?

pH & Buffering pH is relative concentrations of H+ and OH- High H+ & low OH- = acidic Low H+ & high OH- = basic

pH & Buffering pH is relative concentrations of H+ and OH- High H+ & low OH- = acidic Low H+ & high OH- = basic A buffer : prevents sudden or large changes in pH

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ Imagine pH is like a teeter totter & buffering acts like the weight of a person to prevent large changes HCO3 + H+ CO2 & H2CO3 H+ OH-

pH & Buffering OH- When pH increases (becomes more basic) H+ CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ HCO3 + H+ H+ CO2 & H2CO3 OH-

pH & Buffering OH- When pH increases (becomes more basic) H+ CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ HCO3 + H+ CO2 & H2CO3 H+ OH-

pH & Buffering H+ When pH decreases (becomes more acidic) OH- CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ CO2 & H2CO3 OH- HCO3 + H+ H+

pH & Buffering H+ When pH decreases (becomes more acidic) CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ CO2 & H2CO3 HCO3 + H+ OH- H+

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering If we add sodium bicarbonate (NaHCO3) to water, will it become more basic or more acidic? CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering If we add sodium bicarbonate (NaHCO3) to water, will it become more basic or more acidic? CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ HCO3- drives the reaction to the left and uses H+ water becomes more basic

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering If we add acid to change the pH of water with NaHCO3, how much acid will we have to add compared to water with no NaHCO3? CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering If we add acid to change the pH of water with NaHCO3, how much acid will we have to add compared to water with no NaHCO3? CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ The pH of water with HCO3- does not change as quickly because it is buffered

CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ pH & Buffering CO2 + H2O <=> H2CO3 <=> HCO3- + H+ or CO32- + 2 H+ HCO3 + H+ CO2 & H2CO3 H+ OH-

pH & Buffering Carbon dioxide (CO2) is an important buffer in the ocean Many aquatic organisms have a low tolerance for changes in pH

Chemistry of seawater Salt pH Gases Nutrients

Gases Nitrogen 48 Oxygen 36 Carbon dioxide 15 Argon, helium, % by volume in % by volume Gas surface seawater1 in total ocean Nitrogen 48 Oxygen 36 Carbon dioxide 15 Argon, helium, neon, etc. 1 1. Salinity = 36 ppt & temp = 20C

Gases Nitrogen 48 11 Oxygen 36 6 Carbon dioxide 15 83 Argon, helium, % by volume in % by volume Gas surface seawater1 in total ocean Nitrogen 48 11 Oxygen 36 6 Carbon dioxide 15 83 Argon, helium, neon, etc. 1 1. Salinity = 36 ppt & temp = 20C

(fertilizers of the ocean) Nutrients in seawater Nutrient: ion required for plant growth (fertilizers of the ocean)

(fertilizers of the ocean) Nutrients in seawater Nutrient: ion required for plant growth (fertilizers of the ocean) Element Concentration (parts per billion) Nitrogen 500 Phosphorous 70 Silicon 3000