1. G.S. Powell and S. Deperno
8th Grade Science
East Cary Middle School
2013

2. Importance of Oceans
Remove carbon dioxide from the atmosphere and stores it.
Provide oxygen to the atmosphere.
Are home to many species of animals and plants and many complex food webs.
Provide food for the human population.
Used for travel and
shipping.
Drilled for oil.
Mined for minerals.
Recreation.

3. Why is the Ocean Salty?
Salts slowly erode from the Earth’s crust and are carried down rivers into the oceans.
Solids and gases from underwater volcanoes dissolve in the sea.
Hydrothermal vents on ocean floors bring super heated water with many dissolved
minerals
back into
the sea.

4. Why is the Ocean Salty?
The average salinity of seawater is 35 parts per thousand (ppt).
Evaporation and freezing sea ice increases salinity.
Rainfall, run-off from land and melting sea ice decreases salinity.
Salinity is lower in coastal waters, polar seas and near the mouths of large rivers.

5. Dissolved Gases in the Ocean
Cold water holds more gas then warm water.
Lower salinity water holds more gases then higher salinity water.
Deep water holds more gas then shallow water.

6. Dissolved Gases in the Ocean
Waves at the ocean surface release gases from the water into the air.
Phytoplankton use CO2 to photosynthesize and release O2 into the water.
The O2 is used by ocean animals.