1. Ocean Water and Ocean Life
Ch 15
Ocean Water and Ocean Life

2. Composition of Seawater
Salinity
total amount of solid material dissolved in water
Expressed in parts per thousand
Mostly sodium chloride
Sources of Sea Salt
Chemical weathering of rocks on the continents
The Earth’s Interior

3. Processes Affecting Salinity
Decrease Salinity
Precipitation
Sea ice melting
Icebergs melting
Runoff from land
Increase Salinity
Evaporation
Formation of sea ice D

4. Ocean Temperature Variation
Surface water temperature varies with the amount of solar radiation received
Thermocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of temperature with depth

5. Ocean Density Variation
Density is defined as mass per unit volume
Seawater density is influenced by two main factors:
Salinity
temperature

6. Ocean Density Variation
Pycnocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth

7. Ocean Layering
3 main zones – surface zone, transition zone, and deep zone
Surface Zone
Shallow (300 to 450 meters)
Zone of mixing
Sun-warmed zone

8. Ocean Layering Transition Zone Deep Zone
Between surface layer and deep zone
Thermocline and pycnocline
Deep Zone
Sunlight never reaches this zone
Temperatures are just a few degrees above freezing
Constant high-density water

9. Classification of Marine Organisms
Marine organisms can be classified according to where they live and how they move.
Plankton
all organisms—algae(Phytoplankton), animals(Zooplankton), and bacteria—that drift with ocean currents.
Nekton
animals capable of moving independently of the ocean currents (swimming, etc)
Benthos
organisms living on or in the ocean bottom

10. Marine Life Zones
Three factors are used to divide the ocean into distinct marine life zones:
the availability of sunlight
the distance from shore
the water depth.
Availability of Sunlight
The photic zone is the upper part of the ocean into which sunlight penetrates.

11. Distance from Shore Intertidal Zone Neritic Zone Oceanic Zone
strip of land where the land and ocean meet and overlap
Neritic Zone
extends from the low-tide line out to the shelf break
Oceanic Zone
beyond the continental shelf

12. Hydrothermal Vents
Zone where seawater seeps into the ocean floor through cracks in the crust.
water temperatures of 100oC or higher support communities of organisms found nowhere else in the world

13. Ocean Productivity
Primary productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis

14. Primary Productivity Polar Oceans Tropical Oceans Temperate Oceans
Photosynthesis limited by low solar energy
Tropical Oceans
Productivity limited by lack of nutrients
Temperate Oceans
Sunlight and nutrient supply controls productivity