1. Properties of Marine Environments
Salt Water
Properties of Marine Environments

2. Density of Water density of water is greatly affected by:
1. temperature: as water is cooled, density decreases, volume increases,
ice forms and floats
2. salinity: when salts are dissolved into pure water, the density of water increases
salts have a greater density than the water; thus freshwater floats on salt water

3. These properties also have important ramifications for marine organisms:
Organisms inhabiting frigid waters must prevent ice crystals from forming within their cells and body fluids (because the expanding ice would rupture their internal structures)
some have evolved a type of antifreeze in their blood, which lowers the freezing point of their internal fluids
others increase the salt content within their tissues to prevent freezing

4. So where does the salt come from?
Chemical constituents of seawater originate from 6 sources:
1. degassing (releasing of volatile chemicals) that began after the planet's formation and continues today during volcanic activity
2. erosion of sediments and basalts on land by weathering
3. seawater reactions with basalt extruded under the sea that release chemicals into seawater
4. biological processes that produce organic chemicals and cycle bioreactive elements
5. photochemical reactions that occur in the upper pelagic waters
6. radioactive decay of elements that yield other elements

5. What is it made of?
seawater contains almost every known naturally occurring element, but the most abundant materials are chloride and sodium (which is why seawater tastes like table salt)
Component
Concentration
Percentage of Salinity
chloride
18.98
55.03
sodium
10.56
30.59
sulfate
2.65
7.68
magnesium
1.27
3.68
calcium
0.4
1.18
potassium
0.38
1.11
bicarbonate
0.14
Despite containing so many different chemicals salt water is still made up of 96.5% H20 molecules

6. How is it measured? Salinity can be measured two ways:
Specific Gravity
The specific gravity of a substance is a comparison of its density to that of water and is written as a decimal.
Typical s.g. of ocean water is 1.025
Parts Per Thousand
The measure of the amount of dissolved substance per thousand units of the other.
- Typical ppt of ocean water is 35 Written as 35%0

7. How does it behave? Salinity varies with depth
surface layers of water are generally well-mixed by waves, winds, and tides and their salinities and temperatures are generally uniform
However; as you travel deeper the density of water changes due to temperature change and can cause water to separate which is called a thermocline.
Similarly water changes in density due to increased salinity which can also cause seperations called haloclines.
Where there is both a thermocline and a halocline, the density of water changes dramatically -- this change is density is called a pycnocline.

8. These major separations ammong salinity temperature and density lead to interesting interactions between surrounding bodies of water, organisms that live within the water, as well as global weather patterns.

9. The Effects of Salinity on Ocean Life
The ability of aquatic organisms to maintain a proper water balance within their bodies (in either salt water or freshwater) is called osmoregulation.

10. Osmoregulation is related to the process of osmosis.
Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration through a semi-permeable membrane.

11. Variations With Depth
The temperature of the ocean also varies with depth.
As depth increases, water temperature decreases. But the decrease is not uniform. There is a very steep drop in temperature between 200 and 1000 meters. This layer of ocean water is called a thermocline.

12. Thermocline
is a permanent boundary that separates the warmer water above from the colder, denser water below.

13. The Effects of Temperature on Ocean Life
Temperature affects the functioning of living things.
When the water temperature is high, fish are more active than when the water temperature is cooler. Ectothermic animals change their internal body temperature when the temperature of the external environment changes.