Freshwater ecosystems include streams, rivers, ponds, lakes, and wetlands. Streams join to form larger rivers. Ponds and lakes have three zones - a littoral zone near shore with plants, an open-water zone where sunlight reaches, and a deep-water zone without sunlight. Wetlands soak up flood waters and replenish groundwater. They include marshes with grasses and swamps with trees. Over time, a lake can fill in with sediment and transform into a forest. The ocean contains diverse ecosystems shaped by temperature, depth, and sunlight. It has zones like intertidal, neritic, oceanic, and benthic that support different life.

1. Freshwater
Ecosystems

2. Stream and river ecoSyStemS
• Water in brooks, streams, and rivers
may flow from meltingmelting ice or snow or
come from a spring
• Each stream of water that joins a
larger stream is called a tributarytributary
• As more tributaries join, the stream
gets strongerstronger and becomes a river

3. stream
tributary
river

4. Pond and Lake ecoSyStemS
Life Near Shore
Littoral zone: area of water closest to the edge of
a lake or pond
Sunlight reaches bottom of littoral zone,
making it possible for algae and plants to grow
Beneath surface of water: algae
Near shore: cattails and rushes
Floating plants: water lilies
Small animals: snails, insects, clams, worms,
frogs, salamanders, turtles, fishes, and
snakes

5. Littoral zone

6. Life Away from Shore
Open-water zone: area of lake or pond that
extends from littoral zone across top of water
Goes as deep as sunlight can reach
Home to bass, trout, and other fishes
Many photosynthetic plankton live in this area

7. Deep-water zone:
beneath open-water
zone where no
sunlight can reach
Catfish, carp,
worms,
crustaceans, fungi,
and bacteria live
here
These organisms
often feed on dead
organisms that sink
from above

8. Three Zones of a Pond or Lake
Open water zone
Deep water zone

9. Wetland Ecosystems
Wetland: area that is sometimes
underwater or whose soil contains a great
deal of moisture
Play important role in flood control—soaks
up large amounts of water during heavy
rains
Water in wetlands moves deeper into
ground, so helps replenish underground
water supplies

10. Marshes
Treeless wetland ecosystem where
plants, such as grasses, grow
Common marsh plants: grasses, reeds,
bulrushes, and wild rice
Common animals: muskrats, turtles,
frogs, and birds

11. Swamps
Swamp: wetland ecosystem in which
trees and vines grow
Found in low-lying areas and beside
slow-moving rivers
Most swamps are flooded part of
the year, depending on rainfall
Swamp plants: poison ivy, orchids,
water lilies
Swamp animals: fishes, snakes, and
birds

12. From a Lake to a Forest
Did you know that a lake or pond can
disappear?
Water entering a standing body of
water usually carries nutrients and
sediment—these settle at the bottom
of the lake
Dead leaves and decaying matter
also settle at bottom of pond or lake
Bacteria decomposes this material

13. This process uses oxygen in the water
Loss of oxygen affects the kinds of animals
that survive in a pond or lake

14. Over time, pond or lake fills with sediment
and plants start to grow in new soil
Eventually, the wetland can become a
forest

15. Marine ecosysteMs
• Shaped by abiotic factors: water,
temperature, water depth, amount of
sunlight
• Very diverse: ocean contains whales, the
largest animals on Earth
• Tiny plankton form the base of the ocean’s
food chains

16. • Temperature
– Temperature of ocean water
decreases as depth of water
increases
– Surface zone is warm, top
layer; surface currents mix the
water
– Thermocline in this zone,
temperature decreases with
increased depth
– Deep zone bottom layer of
water; averages a chilling 2
degrees C

17. Get in the Zone!
• Major ocean
zones: intertidal,
neritic, oceanic,
benthic
• Intertidal Zone
place where ocean
meets land and is
exposed to air for
part of the day

18. • Neritic Zone
ocean floor slopes
downward, water is
warm and receives
lots of sunlight
–Corals, sea
turtles, fish,
dolphins

19. • Oceanic Zone sea
floor drops sharply,
deep water
– Animals often get food
from material that
sinks down from
ocean surface

20. • Benthic Zone
ocean floor; does
not get much
sunlight; very deep
–Bacteria get
energy from
chemicals that
escape from
thermal vents
on ocean floor

21. A Closer Look
• Through
evaporation, the
ocean provides most
of the water that
makes up Earth’s
precipitation

22. Intertidal Areas
• Coral Reefs most found in neritic zone
• Estuaries area where fresh water from
streams and rivers spills into ocean
– Fresh water and salt water are always mixing, so
amount of salt in water is always changing

23. • The Sargasso
Sea found in
middle of Atlantic
Ocean
–Contains floating
rafts of algae
called
sargassum

24. • Polar Ice the
Artic Oceans and
the ocean around
Antarctica
–Ice water rich in
nutrients, which
support large
numbers of
plankton