1. Aquatic Ecosystems

2. Aquatic Ecosystems
The major kinds of aquatic environments are streams and rivers, lakes, wetlands, estuaries, and oceans.
Each of these can be subdivided further with respect to many factors.

3. Aquatic Ecosystems
In aquatic ecosystems, depth, water temperature, flow rate, and oxygen and nutrient concentrations are the dominant physical factor
Many of the producers in many aquatic ecosystems are single-celled algae
Aquatic ecosystems have been classified by salinity, water movement, and depth
Unlike terrestrial ecosystems, defining aquatic ecosystems according to vegetation would be impossible.

4. Flowing Water: Streams and Rivers
All aquatic ecosystems interact with the terrestrial biomes that surround them
Streams receive runoff, groundwater, and organic matter from the surrounding land
A variety of organisms live their lives in both aquatic and terrestrial environments

5. Flowing Water: Streams and Rivers
Could you name some other interactions between aquatic ecosystems and terrestrial biomes?
Frogs and salamanders, for example, have aquatic larval stages and terrestrial adult stages
Some terrestrial animals feed on organisms that grow in streams and lakes
Many organisms with aquatic larval stages, such as mosquitoes, feed on terrestrial organisms

6. Flowing Water: Streams and Rivers
Stream and river systems are referred to as lotic systems
Flowing water erodes
Rivers and streams are created by erosion
Most streams and rivers are older than lakes – although they move around more
lotic systems-applied to flowing water systems

7. Flowing Water: Streams and Rivers
Streams form wherever precipitation exceeds evaporation
Streams grow with distance as they join together with rivers

8. Flowing Water: Streams and Rivers
River continuum concept-ecosystems are more complex and more productive downstream because water flows more slowly and becomes warmer and richer in nutrients.
The River Continuum Concept describes the physical processes (geology, climate) outside of a river that effect the biological processes (vegetation) along a river, which effect the physical and biological processes within a river (temperature, nutrients).

9. Flowing Water: Streams and Rivers
Riffle areas are where water runs rapidly over a rocky substratum
Water is well oxygenated in riffles

10. Flowing Water: Streams and Rivers
Pools are deeper stretches of more slowly moving waters
Pools tend to accumulate silt and organic matter

11. Flowing Water: Streams and Rivers
Are these two areas productive or unproductive?
Both areas tend to be unproductive because the nutrients needed for life are washed away in riffles, whereas the oxygen and sunlight needed for life are lacking in pools.

12. Flowing Water: Streams and Rivers
Streams lack the richness and diversity of life
Toward the headwaters of rivers, the productivity of algae and other photosynthetic organisms tend to be low
Riparian zones are transitional areas between the aquatic system and adjacent land
Riparian zones are influenced by seasonal flooding and elevated water tables

13. Flowing Water: Streams and Rivers
Much of the food web of headwater ecosystems depends on leaves and other organic matter
Organic material that enters the aquatic ecosystem the outside is termed allochthonous
leaves and other organic matter fall or washes into streams from surrounding vegetation
uh-lok-thuh-nuhs

14. Flowing Water: Streams and Rivers
The larger the river , the more its organic material is autochtonous, originating where it is found

15. Flowing Water: Streams and Rivers
As you move downstream, rivers become wider, slower moving, more nutrient laden, and more exposed to sunlight
Nutrients and sunlight support growth of algae and plants

16. Flowing Water: Streams and Rivers
Lotic systems are sensitive to any modification of their water flow
Rates of flow, water temperature, and sediment patterns are all altered
Could you name one major modification?

17. Flowing Water: Streams and Rivers
Dams are built for flood control, to provide water for irrigation, or to generate electricity
Water behind dams becomes warmer, and bottom habitats become choked with silt, destroying habitat for fish and other aquatic organisms
Using dams for flood control changes the seasonal cycles of flooding
Dams disrupt the natural movement of aquatic organisms

18. Standing Water: Lakes and Ponds
Referred to as lentic systems, distinguished by non-flowing waters
Range in size from small, temporary rainwater to lakes that
are about a mile in depth
Example: Lake Baikal,
in Russia, contains about
1/5th of all the fresh
water at the surface of the
earth.

19. Standing Water: Lakes and Ponds
Many lakes and ponds are
formed by the
retreat of glaciers
Glaciers leave
behind gouged-out
basins and blocks
of ice buried in
glacial deposits
Example: The
Great Lakes of North
America formed in glacial
basins

20. Standing Water: Lakes and Ponds
Lakes are also formed in geologically active regions
Vertical shifting of blocks of the earth’s crust creates basins w/in water accumulates

21. Standing Water: Lakes and Ponds
Oxbow lakes are broad bends of the former river cut off by shifts in the main channel

22. Standing Water: Lakes and Ponds
Lakes are subdivided into several ecological zones, each of which has distinct physical conditions
Littoral zone
Limnetic zone
Benthic Zone

23. Standing Water: Lakes and Ponds
Littoral zone is the shallow zone around the edge of a lake or pond w/in which one finds rooted vegetation
Limnetic zone is the open water where producers are floating single-celled algae, phytoplankton.

24. Standing Water: Lakes and Ponds
The sediments at the bottoms of lakes and ponds make up the benthic zone
The benthic zone provides habitat for burrowing animals and microorganisms

25. Standing Water: Lakes and Ponds
Are lakes and ponds permanent?
Most temporary ponds can dry out each year
Most small temperate lakes that formed when glaciers retreated will gradually refill in w/ sediment until there is no open water
What will happen to the former aquatic ecosystem?
Small temporary ponds can dry out each year, often multiple times during a season
Most small temperate lakes that when glaciers retreated will gradually fill in with sediment until there is no open water
The formerly aquatic ecosystem will slowly change into a terrestrial ecosystem, first a wet meadow and later the natural terrestrial biome of the region

26. Wetlands
Areas of land consisting of soil that is saturated w/ water and supports vegetation specifically adapted to such conditions

27. Wetlands What are some examples of wetlands? Swamps, marshes, and bogs
Salt marshes and mangrove wetlands associated w/ marine envrionments

28. Wetlands
Most of the plants can tolerate low oxygen concentrations in the soil. Many are specialized for anoxic conditions and grow nowhere else
Wetlands provide important habitat for a wide variety of animals
Wetlands protect coastal areas from the ravages of hurricanes and other storms
Wetland sediments immobilize potentially toxic or polluting substances dissolved in water

29. Estuaries Estuaries are found at the mouths of rivers
Are unique because of their mix of fresh and salt water
Are abundantly supplied w/ nutrients and sediments carried downstream by rivers
Estuaries tend to be areas of sediment deposition
Supports high biological productivity

30. Marine Aquatic Systems
Oceans cover the largest portion of the earth
Variation in marine environments comes from differences in temperature, salinity, depth, currents, substrata, and tides
What does depth influence?
Depth influences light and pressure.

31. Marine Aquatic Systems
The littoral zone (also called
the intertidal zone) extends between the highest and lowest tidal water levels
Exposed periodically to air
Ecological conditions w/in
the littoral zone change
rapidly as the tide flows
in or out

32. Marine Aquatic Systems
The neritic zone extends to depths of about 200m, which correspond to the edge of the continental shelf
Region of high productivity
The sunlit surface layers of water are close enough to the nutrients in the sediments below that strong waves can move them to the surface

33. Marine Aquatic Systems
The oceanic zone is beyond the neritic zone where the seafloor drops rapidly to great depths
In the oceanic zone, nutrients are sparse and production is strictly limited
The seafloor beneath the oceanic zone is the benthic zone.

34. Marine Aquatic Systems
Both the neritic and oceanic zones are subdivided vertically into a photic zone
In the photic zone, there is sufficient light for photosynthesis

35. Marine Aquatic Systems
Organisms in the aphotic zone depend mostly on organic material raining down from above

36. Marine Aquatic Sytems
What other ecosystem could be compared to the open ocean?
What other ecosystem could be compared to the tropical rainforest?

37. Marine Aquatic Sytems
Coral reefs are like tropical rainforests, both in the richness of their biological production and the diversity of their inhabitants
Reef-building corals are found in shallow waters of warm oceans
Coral reefs usually surround volcanic islands, where they are fed by nutrients eroding from the rich volcanic soil and by the deep water currents forced upward by the profile of the island

38. Marine Aquatic Sytems
Coral reefs are doubly productive because photosynthetic algae w/in their tissues generate carbon energy that fuels the coral’s rates of growth