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. 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.

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

Mass per unit volume (stuff in a space) 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

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 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

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

Ocean Environments Two basic environments: benthic zone & pelagic zone

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 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.

North Pacific Garbage Patch