4 5 AQUATIC Ecosystems Benchmark SC 912 L

4. 5 AQUATIC Ecosystems Benchmark: üSC. 912. L. 17. 2 Explain the general distribution of life in aquatic systems as a function of chemistry, geography, light, depth, salinity, and temperature. 1

Objectives Explain how depth, salinity, and temperature affect life in an aquatic system Explain how chemistry, geography, and light affect life in an aquatic system 2

Essential Question �What are the major differences between freshwater and marine ecosystems? �How do these differences affect the organisms that live there? 3

Aquatic Ecosystems Fresh Salt 4

Light in Aquatic Ecosystems • Imagine you are a SCUBA diver, as you go deeper into the ocean, what would you see? • NOT MUCH • As you travel deeper into the ocean, light decreases 5

Light in Aquatic Ecosystems • Divided into 2 zones: photic and aphotic 6

Light in Aquatic Ecosystems Photic Zone Aphotic Zone ØThe photic zone is the region where light is able to penetrate Ø The aphotic zone is the region where light is NOT able to penetrate ØProducers can live here Ø Producers cannot live here because photosynthesis cannot occur ØPhotosynthesis happens here Ø Chemosynthesis occurs instead 7

Check for Understanding In which of the following marine zone is light able to penetrate? a. Benthic Zone b. Estuary c. Photic Zone d. Biosphere. 8

Salinity • Salinity is the amount of salt dissolved in a liquid • Does the ocean have more or less salinity than the water from your faucet? 9

Salinity Changes in the Ocean • If there is more evaporation (drying) than precipitation (rain) then the salinity increases • since salt is not evaporated into the atmosphere • If there is more precipitation (rain) than evaporation (drying) then the salinity decreases 10

Salinity Changes • The thawing of large icebergs (made of frozen fresh water and lacking any salt) will decrease the salinity while the actual freezing of seawater will increase the salinity temporarily 11

Temperature in Aquatic Ecosystems • The temperature of seawater varies with the amount of sun that hits that area • Would the temperature be higher in the photic zone or aphotic zone? • PHOTIC ZONE (sun penetrates) 12

Temperature in Aquatic Ecosystems • Do animals prefer warm water or cold water? • Will most organisms be found in the shallow or deep ocean? 13

Gases in Aquatic Ecosystems • The amount of dissolved gases in seawater depends on the types of life forms (plants and animals) that are present • Lots of plants = Lots of oxygen • Few plants = Lots of carbon dioxide 14

Nutrients in Aquatic Ecosystems • Plants need nutrients to live: • Phosphorous • Nitrogen • These nutrients are found in animal feces, which sinks to the bottom of the ocean • The majority of nitrogen and phosphorous nutrients are found in the deep and only come to top during upwelling 15

WE DO: Venn Diagram • Lay out the contents of your envelope and decide which apply to the photic zone and which apply to the aphotic zone. Create a Venn Diagram. 16