Lecture 14
Freshwater Ecosystems
Ozgur Unal
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Why is this globe of Earth blue colored?
Where does water exist on Earth?
Ocean, sea, river, lake, pond etc.
Most of the water on Earth is salty ----> 97.5 %
The rest is freshwater ----> 2.5 %
Different ecosystems are present in each type of water.
Freshwater, transitional and marine ecosystems
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68.9 % of freshwater ecosystems is contained in glaciers.
30.8 % is groundwater.
The rest, 0.3 %, is found in lakes, ponds, wetlands or rivers.
Almost all of the freshwater species live in this 0.3 %.
Rivers and Streams:
Water flows in one direction.
Headwater is the source where the flow begins.
The speed of flow depends on the slope.
Sediment is material that is deposited by water, wind or
glaciers.
As the slope levels, the sediment is deposited in the form of
mud, silt or sand.
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Rivers and Streams:
The characteristics of rivers and streams change as they
flow from the source to the mouth.
Interactions between water and wind add significant
amount of oxygen to the water.
Interactions between land and water result in erosion and
nutrient availability.
The currents in a fast moving rivers and streams prevents
much accumulation of organic material and sediments.
In slow moving water, plants can root themselves into the
stream bed.
Other organisms (crab, insects, fish, frog etc) can live in
calm water.
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Lakes and Ponds:
An inland body of standing water is called a lake or a pond.
Depending on the season, the temperature of water in a
lake or pond changes (Check Figure 3.22)
Nutrient poor lakes are called oligotrophic lakes, often
found high in the mountains.
Nutirent rich lakes are called eutrophic lakes, usually are
found at lower altitudes.
Lakes and ponds are divided into 3 zones.
Littoral zones is the closest to the shore and rich in oxygen.
Limnetic zone is the open water area that is well lit.
Profundal zone is the deep region where there is not much
light and oxygen.
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Lecture 15
Transitional Aquatic Ecosystems
and Marine Ecosystems
Ozgur Unal
6
In many areas, aquatic ecosystems do not look like a stream
or a pond or even an ocean.
Many aquatic environments are a combination of two or
more different environments.
In transitional aquatic ecosystems land and water or
saltwater and freshwater intermingle.
Wetlands
Areas of land such as marshes, swamps and bogs that are
saturated with water and that support aquatic plants are
called wetlands.
Wetlands have high levels of species diversity.
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Estuaries:
An estuary is an ecosystem that is formed where freshwater
from a river or stream merges with salt water from the ocean.
Estuaries are places of transition that are inhabited by a
wide veriaty of species.
Algae, seaweeds and marsh
grasses are the dominant
producers.
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Earth is sometimes called “the water planet”.
Marine ecosystems have a significant impact on the planet.
For example: Through photosynthesis, marine algae
consumes CO2 and produce over 50 % of the atmosphere’s
oxygen.
Evaporation of water from oceans provides the majority of
precipitation.
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Intertidal zone: A narrow band where the ocean meets land.
Organisms in this zone are adapted to constant changes
that occur as daily tides and waves.
Intertidal zone is further
divided into veritcal zones.
Check Figure 3.26!
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Open Ocean Ecosystems: Divided into three major zones:
Pelagic zone, abyssal zone and benthic zone.
Pelagic zone has photic
zone and aphotic zone.
Photic zone (about 200 m
deep) gets sunlight.
Aphotic zone is dark and
colder.
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Benthic zone is the area along the ocean floor that consists
of silt, sand and dead organisms.
As the depth increases, less sunlight penetrates the deeper
water and temperature decreases.
Abyssal zone is the deepest region in the ocean.
Water in this zone is very cold.
Hydrothermal vents spew large amounts of water,
hydrogen sulfide and other minerals  chemosynthesis
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Coastal ocean and coral reefs:
World’s largest coral reefs is off the Southern coast fo
Florida.
Most diverse ecosystems.
Coral reefs form natural barriers along continents that
protect shorelines from erosion.
The dominant organist in coral
reefs are corals with a hard stony
framework.
Coral polyps have symbşotic
relationship with algae.
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