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Ocean Water. Chapter 20. Properties of Ocean Water. Dissolved gases Primarily N2, O2, CO2 Gases enter from rivers, underwater volcanic eruptions, released by organisms, and mostly from the atmosphere.

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Ocean water

Ocean Water

Chapter 20

Properties of ocean water
Properties of Ocean Water

  • Dissolved gases

    • Primarily N2, O2, CO2

    • Gases 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)

Ocean water

  • 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.

Ocean water

  • Temperature

  • Varies 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+)

  • Thermocline

    • Area of water that

      separates warm

      surface water and

      very cold deep water

  • Deep Water

    • Usually about 2 ˚C

    • Holds more dissolved

      gases than warmer,

      shallow water

Ocean water

  • Density

  • Mass 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

Ocean water

  • 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 oceans
Life in the Oceans

  • Life depends on essential nutrients and sunlight

  • Marine 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

Ocean water

  • Marine Food Webs

  • Most marine organisms live within the upper 100m of water.

  • Plankton – free floating microscopic

    • Phytoplankton - photosynthetic

    • Zooplankton – animal-like/non-photosynthetic

  • Nekton – swimmers

  • Benthos – bottom


  • Distribution of marine

    life depends on amount

    of sunlight, water

    temperature, and water


Ocean water

Ocean resources
Ocean Resources

  • Freshwater is available through desalination

  • Mineral and Energy Resources include:

    • Petroleum – drilled from beneath the sea floor

    • Nodules – sources of iron, copper, nickel, cobalt, phosphates.

  • Food

    • Fishing

    • Aquaculture

Ocean water pollution
Ocean Water Pollution

  • Oceans 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.