Ch 15

1. 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

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 • 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 • Thephotic zone is the upper part of the ocean into which sunlight penetrates.

11. Distance from Shore • Intertidal 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 • Photosynthesis limited by low solar energy • Tropical Oceans • Productivity limited by lack of nutrients • Temperate Oceans • Sunlight and nutrient supply controls productivity