Ocean Water

1. Ocean Water Chapter 20

2. 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)

3. 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.

4. 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

5. 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

6. 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.

7. 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

8. 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 dwellers • Distribution of marine life depends on amount of sunlight, water temperature, and water pressure

9. Ocean Environments • Two basic environments: benthic zone & pelagic zone

10. 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

11. 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.

14. North Pacific Garbage Patch