1. Lecture 14 Freshwater Ecosystems Ozgur Unal
NIS - BIOLOGY
Lecture 14
Freshwater Ecosystems
Ozgur Unal

2. The Water on Earth 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

3. Freshwater Ecosystems
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.

4. Freshwater Ecosystems
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.

5. Freshwater Ecosystems
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.

6. NIS - BIOLOGY Lecture 15 Transitional Aquatic Ecosystems
and Marine Ecosystems
Ozgur Unal

7. Transitional Aquatic Ecosystems
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.

8. Transitional Aquatic Ecosystems
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.

9. Marine Ecosystems 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.

10. Marine Ecosystems
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!

11. Marine Ecosystems
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.

12. Marine Ecosystems
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

13. Marine Ecosystems 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.