Ocean WaterChapter 20

Properties of Ocean WaterDissolved gases

Primarily N2, O2, CO2Gases enter from rivers, underwater volcanic

eruptions, released by organisms, and mostly from the atmosphere.

Colder water dissolves gases more readily (this is why your soda does not go flat as quickly when kept in the refrigerator)

Dissolved Solids Most abundant are: chlorine, sodium, magnesium,

sulfur, calcium, potassium (salts)Come from volcanic eruptions, chemical weathering

of rock on land, chemical reactions between sea water and sea-floor rock.

As water evaporates, minerals and salts are left behind.

Salinity is measure of amount of dissolved salts and other solids in a liquid.

Salinity is affected by precipitation (reduces salinity by adding fresh water), evaporation and freezing (increases salinity by removing only water molecules).

Examples: Global Ocean average salinity is 34.7%. Red Sea more than 40% salinity due to hot, dry climate causing high levels of evaporation.

TemperatureVaries depending on depth and location.Surface water (100 to 300m) heated by solar radiation

Decreases at higher latitudes (polar water is cooler -1.9˚C than tropical water 30˚C+)

ThermoclineArea of water that separates warm surface water and very cold deep water

Deep WaterUsually about 2 ˚CHolds more dissolved gases than warmer, shallow water

DensityMass per unit volume (stuff in a space)

Density of pure water = 1g/cm3

Affected by: salinity – increase in dissolved solids increases mass of

water increasing its density. Ocean water density ranges from 1.0261g/cm3 and 1.0281g/cm3

Temperature – colder water is more dense than warmer water. Most dense water is found in polar regions.

Denser water sinks, less dense water rises

Color Water color is determined by the way it

absorbs or reflects sunlight.White light contains all visible wavelengths

(ROYGBIV)Water tends to absorb most of the wavelengths.

Only blue wavelengths are reflected.Phytoplankton absorb red and blue light and

reflect green. Therefore, large populations of phytoplankton affect the shade of blue of the ocean.

Life in the OceansLife depends on essential nutrients and

sunlightMarine organisms help maintain the chemical

balance of the ocean water by removing some nutrients and gases while returning others.Example: photosynthetic marine plants absorb

carbon dioxide from ocean water and release oxygen.

Upwelling – the movement of deep, cold, nutrient rich water to the surface due to density changes

Marine Food WebsMost marine organisms live within the upper 100m

of water.Plankton – free floating microscopic

Phytoplankton - photosyntheticZooplankton – animal-like/non-photosynthetic

Nekton – swimmersBenthos – bottom dwellersDistribution of marine life depends on amount of sunlight, water temperature, and water pressure

Ocean EnvironmentsTwo basic environments: benthic

zone & pelagic zone

Ocean ResourcesFreshwater is available through desalinationMineral and Energy Resources include:

Petroleum – drilled from beneath the sea floorNodules – sources of iron, copper, nickel,

cobalt, phosphates.Food

FishingAquaculture

Ocean Water PollutionOceans have been used as dumping grounds for

wastes including garbage, sewage, and nuclear waste

Increased human world-wide population and increased use of toxic substances have reduced the ocean’s ability to absorb & renew itself.

Pollution has resulted in destroyed clam and oyster beds, sea birds and marine mammals become tangled in trash, and beaches have been closed because of sewage and oil spills.

Traces of mercury , DDT (insecticide), and lead (from gasoline) are so high in some areas that fish are unsafe for human consumption.

North Pacific Garbage Patch