Aquatic Ecosystems
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Transcript Aquatic Ecosystems
Aquatic Ecosystems
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.
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
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
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
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
Flowing Water: Streams and Rivers
Streams form wherever
precipitation exceeds
evaporation
Streams grow with distance
as they join together with
rivers
Flowing Water: Streams and Rivers
River continuum conceptecosystems are more complex and
more productive downstream
because water flows more slowly
and becomes warmer and richer in
nutrients.
Flowing Water: Streams and Rivers
Riffle areas are where
water runs rapidly over a
rocky substratum
Water is well oxygenated
in riffles
Flowing Water: Streams and Rivers
Pools are deeper
stretches of more slowly
moving waters
Pools tend to
accumulate silt and
organic matter
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.
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
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
Flowing Water: Streams and Rivers
The larger the river , the more its
organic material is autochtonous,
originating where it is found
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
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?
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
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.
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
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
Standing Water: Lakes and Ponds
Oxbow lakes are broad bends of the former river cut
off by shifts in the main channel
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
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 singlecelled algae, phytoplankton.
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
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?
The formerly aquatic ecosystem will slowly change into a
terrestrial ecosystem, first a wet meadow and later the natural
terrestrial biome of the region
Wetlands
Areas of land
consisting of soil that
is saturated w/ water
and supports
vegetation specifically
adapted to such
conditions
Wetlands
What are some examples of wetlands?
Swamps, marshes, and bogs
Salt marshes and mangrove wetlands associated w/ marine
envrionments
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
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
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.
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
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
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.
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
Marine Aquatic Systems
Organisms in the aphotic zone depend mostly on organic material
raining down from above
Marine Aquatic Sytems
What other ecosystem could be compared to the
open ocean?
What other ecosystem could be compared to the
tropical rainforest?
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
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