1. Unit. 2 Mr. Lara Marine Science Class
The Nature of Seawater
Unit. 2 Mr. Lara Marine Science Class

2. Vocabulary Acid(Acidic) pH Base Thermocline Brackish Water vapor
Buffer
Condense
Condensation
Crystallization
Evaporation
Desalination
Precipitation
Evaporate
Distillation
Filtration
Hydrologic cycle (Water cycle)
Hypersaline

3. Water Cycle

4. Water Cycle Or the Hydrological Cycle.
Over 97 % of the water on earth is to salty to drink .
However nature helps by purifying the water.
Evaporation –liquid water turns into a gas. Water molecules at water’s surface turn into water vapor (gas).

5. Condensation and Precipitation
When molecules of water vapor come together they form a cloud. This process is called condensation.
Condensation comes after vapor form in the water cycle.
When the cloud become saturated, or full, from so many droplets condensing together the droplets fall to the Earth as precipitation
Precipitation can be rain, sleet or snow.

6. Runoff
Some of the water that returns to the earth will wash into the oceans, lakes and rivers.
The rest of the water will get soaked up by the ground and become ground water.
Seawater so much to see, so little to drink
Why can’t you drink seawater?

7. Salt water
Most of the salt in the seawater is sodium chloride (NaCl). This and four other elements make up the 99% of the salt found in the ocean.
The four other are consider trace elements, such as bicarbonate (HCO3) and exist in very small quantities.
Where did these elements in the seawater come from?

8. Salinity: Water and Salt
To better understand the composition of seawater, oceanographers measure the amount of dissolved salts in the ocean.
It is measured in parts of dissolved salts per 1,000 parts of water-or parts per thousand (0/00)
Average salinity in the ocean is ppt or PSU

9. Differences in Salinity
The Salinity in the Ocean differs from one location to the next.
For example: Red Sea has salinity reading of 40 and 41 ppt (PSU).
The Mediterranean Sea has a Salinity reading 38 and 39 parts per thousand.
Both of these seas are consider Hypersaline

10. Why the differences in salinity
Many factors can affecting salinity in the water
Latitude
Proximity to Coast
Evaporation
Rain
Runoff
Freezing of Ice
Melting of Ice
Tides
Temperature

11. Temperatures of the Ocean
The surface temperature of the ocean varies depending on the latitude (it’s distance from the equator ) and season of the Year.
Water at lower depths of the ocean is always colder then higher depths and on the surface
Thermocline- a layer of water in the ocean where the temperature of the water changes rapidly

12. Light in the Ocean
On average, light reaches to about 200 meters below the surface of the ocean, or two foot ball fields
Light is not adequate beyond about 100 meters to support photosynthesis (food making) plants and animals
Color also disappears as you increase depth .
ROYGBIV

13. Dissolved Gasses in Seawater
Seawater also contains dissolved gasses that come from the mixing with air in the atmosphere.
Both plants and animals play a roles in the removing and replacing of gases in the seawater.
What do plants take in?
What do animals take in?

14. Photosynthesis and Respiration
Plants take in oxygen and carbon dioxide.
Photosynthesis, is how plants make food by using carbon dioxide, water, and sunlight. While release oxygen.
Once plants have made their food they need to convert it into energy in process called cellular respiration
Plants and animals both do respiration, In respiration oxygen is taken in and Carbon dioxide released

15. CO2 Buffering Seawater Carbonate buffering system.
By increasing the concentration of CO2 you are shifting the equilibrium of the carbonate system in such a way that , in the end the concentration of HCO3(-) and H(+) ions is what causes the PH to drop
I.E. acidification
The decrease in CO3(2-) is what leads to the decrease in Aragonite and Calcite saturation
This is a big problem

16. Ocean Acidification
Organisms that use this minerals for calcification ( corals, clams, forams crabs, ect.)
When CO2 dissolves in the seawater it combines with water to form hydrogen (H+) and bicarbonate (HCO3-) ions
CO2 + H20  H(+) + HCO3(-)
Some Hydrogen ions combine with carbonate (C03(2-) ions to form additional bicarbonate
H(+) + CO3(2-)  HCO3(-)

17. Desalination: A New Source of Freshwater
Freshwater is in short supply.
Increase in the world’s population and industry have endangered this essential resource
Scientist have developed Desalination methods – or ways to remove salt from the seawater into freshwater
Very expensive method

18. Three types of Desalination
Distillation- the most successful method- is a process by which water is heated in a domed structure until it evaporates and becomes water vapor
Evaporated water does not contain salt . The evaporated water then condenses on the dome to run down its surface into troughs

19. Filtration and Crystallization
Water is filtered through a special membranes or materials that allow water to passes through but trap salt and other impurities.
Crystallization water is frozen. Then ice crystals can then removed and melted leaving the salt behind

20. Other terms and facts
Ph range in the ocean is 7.5 to 8.5 which supports marine life Most of Florida’s freshwater supply comes from ground water Brackish water is the termed used for lower salinity water fresh and salt water combined.