1.
2.
3.
4.
Compare and Contrast What are some ways in
which life in an aphotic zone might differ from life
in a photic zone
Apply Concepts What is a wetland and why are
they important
Predict How might a dam upriver affect an
estuary at the river’s mouth
Review List the three major marine ecological
zones and give two abiotic factors for each.
CH 4 ECOSYSTEMS AND COMMUNITIES
4.5 Aquatic Ecosystems

Nearly three-fourths of Earth’s surface is
covered with water.

Aquatic organisms are affected primarily by
the water’s depth, temperature, flow, and
amount of dissolved nutrients.
Water Depth


Sunlight penetrates only a relatively short
distance through water
Photic zone
 Sunlit
region near the surface in which
photosynthesis can occur
 May be as deep as 200 meters in tropical seas
 May be much, much less.


Photosynthetic algae (phytoplankton) live in
the photic zone
Zooplankton (tiny free-floating animals)eat
phytoplankton.

Aphotic zone
 Photosynthesis

cannot occur
Benthic zone
 Rocks
and sediments and on bottom of lakes and
streams

Benthos
 Aquatic
organisms that live in the benthic zone.
Temperature and Currents



Warmer near the equator and colder near the
poles
Deepest parts of lakes and oceans are often
colder than surface waters
Currents can carry different temperature
waters.
Nutrient Availability

Not consistent in aquatic habitats.

Freshwater ecosystems can be divided into
three main categories: rivers and streams,
lakes and ponds, and freshwater wetlands.
Rivers and Streams




Often originate from underground water
sources in mountains or hills
Have plenty of dissolved oxygen but little plant
life near source
Sediments build up and plants establish
themselves downstream
Depend on terrestrial plants and animals that
live along their banks for food.
Lakes and Ponds


Based on a combination of plankton and
attached algae and plants
Water flows in and out of lakes and ponds and
circulates between the surface and the
benthos, distributing heat, oxygen, and
nutrients.
Freshwater Wetlands
•
Wetland
–
•
•
•
•
Water either covers the soil or is present at or
near the surface for at least part of the year
May have flowing water
Nutrient-rich, highly productive, and serve as
breeding grounds for many organisms
Purify and filter water
Freshwater bogs, freshwater marshes, and
freshwater swamps.
Estuary




Saltwater wetland
Where river meets the sea
Affected by tides
Spawning and nursery grounds for many
ecologically and commercially important fish
and shellfish species.
Marine Ecosystems

Ocean divided into zones based on depth and
distance from shore:
 Intertidal
ocean.
zone, the coastal ocean, and the open
Intertidal Zone


Submerged in seawater at high tide and
exposed to air and sunlight at low tide
Barnacles and seaweed attached to rocks.
Coastal Ocean


Extends from the low-tide mark to the outer
edge of the continental shelf
Water is brightly lit, and is often supplied with
nutrients- very productive.
Open Ocean




Begins at the edge of the continental shelf and
extends outward
More than 90 percent of the world’s ocean
Depth ranges from 500 m along to more than
10,000 m
Divided into photic and aphotic zones.
Photic Zone


Typically has low nutrient levels and supports
only small phytoplankton
Most photosynthesis occurs in the top 100
meters of the open ocean.
Aphotic Zone


Permanently dark
Deepest parts of the ocean.