1. OCEAN WATER AND OCEAN LIFE

2. 15.1 The Composition of Seawater
Salinity is the total amount of salt dissolved in water, expressed in parts per thousand (‰)
The salinity of seawater is 3.5% or 35 ‰
Most of the salt in seawater is sodium chloride
The sources of salts in seawater is from salts dissolved in runoff from the chemical weathering of rocks and elements from volcanic eruptions
The salinity of seawater varies slightly from 33 ‰to 38 ‰.
The processes that affect salinity are
adding a large amount of fresh water from precipitation, runoff from land, and melting sea ice (decreases salinity)
evaporation (increases salinity)

3. Ocean Temperature variation
1. Ocean temperature variation with latitude – lower sea temperatures are found at higher latitudes (closer to the poles)
2. Ocean temperature variation with depth
The sun’s rays only penetrate to a depth of about 1000 meters
Thermocline – the layer of water between 300 meters and 1000 meters where there is a rapid change in temperature

5. Ocean density variation
Density is mass divided by volume
Density of seawater is affected by salinity and temperature
Density increases the higher the salinity and the lower the temperature
Pycnocline – a layer of water between 300 meters and 1000 meters, there is little mixing between the upper less dense water and the lower more dense water

7. Ocean Layering
Surface zone – water is warmest of uniform temperature, mixed zone
Transition zone – temperature fall rapidly
Deep zone – no sunlight, temperatures constant at a few degrees above freezing, pressures high, cold-high density

8. Classification of Marine Organisms
Plankton – includes all organisms that drift with ocean currents, phytoplankton and zooplankton
Phytoplankton forms the base of the marine food chain, produces much of the oxygen we breathe
Nekton – free swimmers
Benthos - bottom dwelling

10. Marine Life Zones 1. Availability of Sunlight
Photic – upper part of the ocean where sunlight penetrates
Euphotic – surface area where photosynthesis occurs, about 100 meters
Aphotic – sunlight does not penetrate

11. 2. Distance from Shore
Intertidal zone – plants and animals must adapt to crashing waves, periodic drying out, changes in temperature, salinity and oxygen content
Neritic zone – extends from the low-tide zone to the edge of the continental shelf, very productive due to nutrients from land and shallower waters
Oceanic zone- beyond the continental shelf, waters have lower nutrient content

12. 3. Water depth
Pelagic zone – open ocean
Benthic zone – bottom
Abyssal zone – deep ocean floor with extremely high pressure

14. 5.3 Ocean Productivity
Primary Productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis
Photosynthesis is the use of light energy to convert water and carbon dioxide into energy rich glucose molecules
Chemosynthesis is the process by which certain microorganisms create organic molecules from inorganic nutrients using chemical energy
Two factors affect ocean primary productivity – availability of nutrients (nitrogen, phosphorus, and iron) and the amount of sunlight

15. Productivity in Polar Oceans – highly productive due to upwelling of nutrients from the bottom
Solar radiation is the limiting factor
Productivity of Tropical Oceans – productivity is low due to little mixing of the nutrient rich bottom waters with warm surface waters
Nutrients are the limiting factor
Productivity of Temperate Oceans – productivity is limited by both nutrients and availability of sunlight, varies according to season

16. Ocean Feeding Relationships
Marine algae, plants, and bacteria are the basis of the food chain – primary producers
Trophic levels – feeding levels
Transfer efficiency between trophic levels is very inefficient
Food chain is a sequence of organisms through which energy is transferred
Primary producer → herbivore → carnivore
Food web shows the feeding relationship among many organisms