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Ocean Water and Ocean Life 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 Decrease Salinity ◦ ◦ ◦ ◦ Precipitation Sea ice melting Icebergs melting Runoff from land Increase Salinity ◦ Evaporation ◦ Formation of sea ice 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 Density is defined as mass per unit volume Seawater density is influenced by two main factors: ◦ Salinity ◦ temperature Pycnocline is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth 3 main zones – surface zone, transition zone, and deep zone Surface Zone ◦ Shallow (300 to 450 meters) ◦ Zone of mixing ◦ Sun-warmed zone 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 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 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. 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 Zone where seawater seeps into the ocean floor through cracks in the crust. o water temperatures of 100 C or higher support communities of organisms found nowhere else in the world Primary productivity is the production of organic compounds from inorganic substances through photosynthesis or chemosynthesis Polar Oceans Photosynthesis limited by low solar energy Tropical Oceans Productivity limited by lack of nutrients Temperate Oceans Sunlight and nutrient supply controls productivity