1. Lesson 6.3 Aquatic Ecosystems
75% of Earth’s surface is covered by water.

2. What are the basic needs of aquatic life?
CO2 O2
Sunlight
Nutrients- food & minerals

3. Describing Aquatic Ecosystems
Salinity:
Amount of dissolved salt present in water
Salt water, fresh water, or brackish
Photosynthesis:
Light availability
Depth & water clarity
Flowing or standing water
Zones: photic, aphotic, benthic

4. Types of Aquatic Ecosystems
Freshwater Ecosystems
Standing Water- lakes & ponds
Moving Water- rivers & streams
Transitional Communities
Estuaries
Wetlands- bogs/fens, swamps, marshes
Marine Ecosystems
Shorelines
Barrier Islands
Coral Reefs
Open Ocean

5. Freshwater Ecosystems
Usually 0.005% salt
Some exceptions:
Great Salt Lakes-
5-27% salt
Dead Sea- 30% salt
Moving water- high elevations; cold; high O2; trout; streamlined plants
Standing water- lower elevations; warmer; less O2; bass, amphibians; cattails, rushes

6. Freshwater Ecosystems: Ponds, Lakes, Inland Seas
Horizontal zones: littoral and limnetic

7. How is a lake stratified and what lives in each level?
Epilimnion- upper layer of warm water; high light & O2; ex: water striders, phyto- & zooplankton, fish
Thermocline (mesolimnion); middle layer; medium light & O2; ex: phyto- & zooplankton, fish
Hypolimnion- lower layer of cold water; lower light & O2; ex: fish
Benthos- bottom level; no light & little O2; ex: anaerobic bacteria, leeches; insect larvae
Littoral- near the shoreline; cattails, rushes, amphibians, etc.

8. Freshwater Ecosystems: Wetlands
Lesson 6.3 Aquatic Ecosystems
Freshwater Ecosystems: Wetlands
Areas of land flooded with water at least part of the year
Marshes, swamps, bogs, and fens
Prevent flooding, recharge aquifers, filter pollutants, and provide habitats.

9. Freshwater Ecosystems: Rivers and Streams
Lesson 6.3 Aquatic Ecosystems
Freshwater Ecosystems: Rivers and Streams
Bodies of surface water that flow downhill, eventually reaching an ocean or inland sea
Watershed: area of land drained by a river and its tributaries
Characteristics, such as dissolved oxygen, temperature, water speed, organisms, and others, change from source to mouth.

10. Estuaries Where river flows into the ocean or an inland sea
Prevent flooding and soil erosion as well as provide habitats.
Coastal estuaries
brackish; organisms must tolerate wide salinity and temperature ranges
home to salt marshes & mangrove forests
Everglades, Florida, wetlands
Did You Know? Salt marshes and mangrove forests are two of the most productive ecosystems on Earth.

11. Lesson 6.3 Aquatic Ecosystems
Oceans
Currents are driven by water temperature and density differences, wind, and gravity.
Surface winds and heating generate vertical currents that transport nutrients and oxygen.
Horizontal ocean zones: intertidal, neritic, open ocean
Vertical ocean zones: photic, aphotic, benthic
Did You Know? If the water in the oceans evaporated, a 60 m (200 ft) deep layer of salt would be left behind.

12. Ocean Ecosystems
Intertidal: Highly diverse; extreme range of temperature, moisture, and salinity
Neritic: Productive kelp forests and coral reefs provide habitats and help protect shorelines from erosion.
Open ocean: Low productivity due to low light penetration; phytoplankton base of food chain; deep sea organisms and hydrothermal vent communities
Did You Know? Over 90% of ocean water on Earth is in the open ocean zone.

13. What factors influence the availability of those basic needs?
Substances dissolved in water- Nitrates, phosphates, potassium, O2
Suspended matter- (silt, algae) can affect light penetration
Depth
Temperature
Rate of flow
Bottom characteristics (muddy, sandy, or rocky)
Internal convection currents
Connection to or isolation from other aquatic ecosystems.

14. Transitional Communities
ESTUARIES
Where freshwater dumps into ocean
Brackish (less salty than seawater)
Has rich sediments that often form deltas
Productive & biodiverse
Organisms adapted to varying levels of salinity as tide ebbs & flows
“Nursery” for larval forms of many aquatic species of commercial fish & shellfish

15. Transitional Communities
WETLANDS
Land saturated at least part of the year
Swamps- have trees like bald cypress; high productivity
Marshes- no trees; tall grasses; high productivity
Bogs/Fens- may or may not have trees; waterlogged soil with lots of peat; low productivity
Fens- fed by groundwater & surface runoff
Bogs- fed by precipitation
Swamp
Marsh
Bog
Fen

16. Importance of Wetlands
Highly productive- get lots of sunlight, ↑ plants =
↑ animals
Nesting, breeding ground for migratory birds
Slows flooding by absorbing runoff
Silt settles, making water clearer & nutrient rich
Trap & filter water
Natural chemical rxns neutralize and detoxify pollutants
Gives H2O time to percolate thru soil & replenish underground aquifers.
Threats- artificial eutrophication (see slide 13), draining, sedimentation via construction
“Nature’s Septic Tank”

17. Marine Ecosystems SHORELINES
Rocky coasts- great density & diversity attached to solid rock surface
Sandy beaches- burrowing animals
Threats- due to hotels, restaurants, homes on beach, more plant life destroyed, destabilizing soil, susceptible to wind & water erosion
Insurance high; danger of hurricanes, erosion
Build sea walls to protect people but changes & endangers shoreline habitat

18. Marine Ecosystems BARRIER ISLANDS Low, narrow offshore islands
Protect inland shores from storms
Beauty attracts developers = developers destroy land
New coastal zoning laws protect future development

19. MARINE ECOSYSTEMS CORAL REEFS Clear, warm shallow seas
Made up of accumulated calcareous (made of calcium) skeletons of coral animals
Formation depends on light penetration.
Have a symbiotic relationship with algae
Very diverse, abundant (rainforests of sea)
Threats- destructive fishing (cyanide & dynamite to stun fish), pet trade; about 3/4ths have been destroyed

20. What factors can alter aquatic ecosystems?
Natural Succession- normal cycle of pond becoming forest
Artificial Succession- humans add N & P to water via fertilizer & sewage causing succession to happen faster = EUTROPHICATION

21. What factors can alter aquatic ecosystems?
Humans!
Find food
Recreation
Waste disposal
Cooling of power plants
Transportation
Dams, canals