Teacher’s Guide
Lesson 5
Estuarine Habitats - Between Fresh and
Salt Water
Lesson Description
Estuarine habitats represent the area where the oceanic salt water meets
the freshwater flowing downstream in the Hudson River. These areas
represent a mixing of not only the water, but also a habitat that can
support unique plants and animals. The tides impact this area greatly and
the fluctuation of the water level offers many challenges for the flora and
fauna that call this area home.
After having completed the activity on tides, this lesson asks the
students to investigate an estuarine habitat and describe the differences
they find there. It would be helpful for the students to have completed the
lesson on tides before beginning this so that they are aware of the amount
of fluctuation in the water level in their area.
Science Concepts Introduced
• Estuary, habitat, limiting factor, food chain/web.
Process Skills Emphasized
• Cooperative/team skills, data collection.
Technology Used
• Computer with Internet capability recommended.
Learning Outcomes
Students will be able to:
•
Identify different plants characteristic of an estuary;
•
Identify different animals characteristic of an estuary;
•
Explain the effect of the change in water level on the
habitat and its populations;
•
Identify the various estuary zones that are shown on the
diagram; and
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•
Explain what the estuaries would look like upstream or
downstream from their location, based on how the salinity
would change.
Time Requirement
• One to two forty-minute class periods above and beyond
the tide analysis activity. More time will be needed if the
students have the opportunity to actually visit the estuary.
This activity could be extended throughout the year, as the
teacher wishes, noting any changes that occur in plant
and/or animal life.
Instructional Strategies
Students will investigate the characteristics of an estuary habitat. If
students cannot visit an estuary, they can use the diagram to answer
questions given in the student section. Careful attention should be paid to
the extent of water level change due to the tides and a connection should
be made to the plants and/or animals that can be found at each level.
Students will also become familiar with the concept of limiting factors
through this activity, as they will be asked to define limiting factors for
organisms and plants found in estuarine habitats.
One very effective way to investigate estuary organisms is to have the
students draw or construct a food chain and/or food web of the types of
plants and animals found there. Students should be instructed or
reminded of the role of plankton in an estuarine habitat.
If students are going outside to conduct research, they might be given
testing equipment to test the salinity and soil characteristics. If testing can
be done for different types of plankton, this will also add another level of
trophic energy for the students to investigate.
Assessment
Students could be:
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•
Given a diagram of another estuary habitat and asked to
diagram what they might find at each level.
•
Asked to give characteristics of the soil, water level, or
salinity found at each level.
•
Given a food chain or web to fill in with the appropriate
organisms.
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Extensions / Options
• Students could be taken to a number of different sites and compare the
characteristics of those sites, especially with respect to the effect of
water/tide level.
•
Students could also conduct additional research on estuaries, using the
Internet sites listed below.
Key Terms
Estuary, habitat, limiting factor.
Pre-Requisite Knowledge
• Students may or may not have completed the lesson on tides.
Equipment Needed
• Computer with Internet optional.
References
See Website information below.
Handouts
Characteristics of Estuarine Habitats handout for students, student
question sheet.
Websites:
• EPA Office of Water – National Estuary Program
• http://www.epa.gov/owow/estuaries/
•
National Estuarine Research Reserve System – Estuary-Net Program
• http://inlet.geol.sc.edu/estnet.html
•
National Estuarine Research Reserve System – Hudson River
Special Estuaries In the Hudson River Basin
• http://inlet.geol.sc.edu/HUD/index.html
•
Estuary Live! A live camera of an estuary in North Carolina.
• http://www.estuarylive.org/
•
The NYS Hudson River Homepage
• http://www.dec.state.ny.us/website/hudson/
•
The Hudson River Estuary – The Basics
• http://www.dec.state.ny.us/website/hudson/
•
Cornell University – Department of Natural Resources Kids’
Activities – Special Habitats
• http://www.sarep.cornell.edu/Sarep/Kids/facts/ecology/hab
itats.html
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Student Guide
Lesson 5
Estuarine Habitats-Between Fresh and
Salt Water
Introduction
Estuaries are unique habitats formed when freshwater meets the water flowing in from the
ocean. To complicate matters, the water composition and level changes cyclically, due to the rise
and fall caused by the daily tides. What things can survive under these conditions? You are about
to find out!
Learning Outcomes
When you finish this lesson, you will be able to:
•
Identify different plants characteristic of an estuary;
•
Identify different animals characteristic of an estuary;
•
Explain the effect of the change in water level on the habitat and its populations;
•
Identify the various estuary zones that are shown on the diagram;
•
Explain what the estuaries would look like upstream or downstream from their location,
based on how the salinity would change; and
•
Show the feeding relationships and how energy is passed between different organisms in an
estuary using either a food chain or a food web.
Skills Required
• Cooperative/team skills, data collection, research skills.
New Terms
Estuary, habitat, limiting factor.
Quest
Your mission is to identify the kinds of plants and animals that call this place home – what
could live here? The water level is constantly changing, and there is a combination of salt and
freshwater in the area--- who could survive? What are the limiting factors in an estuary? Your
task is to investigate this area to determine the brave organisms that call this place home!
Materials
• Student worksheets
•
Computers with Internet access
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Procedure
You will answer the questions on the worksheet by doing one or more of the following:
•
Investigate using books or materials provided by you teacher.
•
Investigate using information from the Internet (see the websites given below.
•
Go outside to investigate an estuary nearby.
Extensions / Options
This lesson may be extended be taking you to a number of different sites and comparing the
characteristics of those sites, especially with respect to the effect of water/tide level. You may
also be asked to do additional research on estuaries, using the Internet sites listed below.
Assessment
• You may be given a diagram of another estuary habitat and asked to diagram what you might
find at each level.
•
You might also be asked to give characteristics of the soil, water level, salinity, etc., found at
each level.
•
Additionally, you might be asked to complete a food chain or food web using organisms that
you found out about in this investigation.
Handouts
• Handout on characteristics of estuarine habitats, question sheet.
Websites:
• EPA Office of Water – National Estuary Program
• http://www.epa.gov/owow/estuaries/
•
National Estuarine Research Reserve System – Estuary-Net Program
• http://inlet.geol.sc.edu/estnet.html
•
National Estuarine Research Reserve System – Hudson River – Special Estuaries In the
Hudson River Basin
• http://inlet.geol.sc.edu/HUD/index.html
•
Estuary Live! A live camera of an estuary in North Carolina.
• http://www.estuarylive.org/
•
The NYS Hudson River Homepage
• http://www.dec.state.ny.us/website/hudson/
•
The Hudson River Estuary – The Basics
• http://www.dec.state.ny.us/website/hudson/
•
Cornell University – Department of Natural Resources Kids’ Activities – Special Habitats
• http://www.sarep.cornell.edu/Sarep/Kids/facts/ecology/habitats.html
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Student Guide
Lesson 5
Estuarine Habitats-Between Fresh and
Salt Water
(Lee, Cara. 1996)
Although the ocean tidal flow is the energy behind the tides in the Hudson River, not all of the
tidal portion of the river is saltwater. On average the salt water surges as far up as Newburgh,
and freshwater tides continue all the way to the dam in Troy. The inland tide creates a variety of
habitats along the Hudson River. Different habitats can be identified based on specific
characteristics including water levels, water salinity, and soil type. These physical
characteristics allow different flora and fauna to live and utilize the habitat.
Subtidal Zone– below low-tide level; submerged
Deepwater communities are found in the sub-tidal zone. The sub-tidal zone is the area
found below low-tide level or the area that is continuously covered in water, usually by
more than two meters deep. Light does not penetrate very deep into the sub-tidal zone of
the Hudson River. This zone does not support rooted vegetation, however,
phytoplankton grows in the upper layers of the water column. Animals including benthic
or bottom dwelling invertebrates, fish, and fish-eating predators live or depend on this
zone.
Intertidal Zone– between average low- and high-tide levels;
The inter-tidal zone is split up into a variety of communities each with their own distinct
physical characteristics. One distinction that divides these habitats is the mean tide level.
There is an upper inter-tidal zone and a lower inter-tidal zone. The upper inter-tidal zone
is the area between the mean tide level and the mean high tide level. The lower intertidal zone is the area between the mean low tide level and the mean tide level. The
second distinction between these communities has to do with whether the water is
saltwater, brackish or freshwater. Brackish water supports different organisms then
freshwater. A few examples of communities found in the intertidal zones are high salt
marsh, low salt marsh, brackish tidal marsh, and freshwater tidal marsh. Along the
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Hudson River brackish tidal marshes occur between New York City to Newburgh, and
freshwater tidal marshes are found from Newburgh to Troy.
Irregularly Flooded Zone– above average high-tide level; this area is flooded with spring high
tides and storm events
This community along the river is called the tidal swamp. The tidal swamp is less
frequently observed along the Hudson River. It occurs where the change from inter-tidal
communities to upland communities is more gradual, yielding the tidal swamp.
Upland – area beyond the reach of tides, only the highest of storm-related tides may reach
Although this community is not tidally influenced, upland areas play important roles in
estuarine ecosystems. These habitats that occur adjacent to wetland habitats act as
watershed buffers to the water draining into the river or its tributaries.
Extension: Human impacts on estuarine habitats
Once you have determined how the tide behaves near your community it will be easier to
interpret what kind of habitats are found along the Hudson River and it’s tributaries. As an
extension activity you can take a field trip to a local wetland and explore the flora and fauna with
field guides. This will give students a connection with what they have learned in class to the
natural world.
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Student Guide
Lesson 5
Estuarine Habitats-Between Fresh and
Salt Water
Worksheet for looking at Estuaries of the Hudson River
1. How much does the water level change in this estuary due to the tides?
2. What types of plants are found in this type of area? Be as specific as you can – identify the
plants by groups or by species if at all possible!
3. What characteristics do these plants have in common? What adaptations help the plants to
survive in this changeable habitat?
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4. What does the soil of this area look like? Do you see anything that makes this soil
different from soils found in another area?
5. What types of animals would be found in this area? Identify birds, fish, invertebrates and
other animals that might call this area home. Would you find these animals in other
habitats or only in an estuary?
6. What characteristics do these organisms possess that allow them to live in this habitat? Be
as specific as you can! What adaptations allow these animals to live here?
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7. What is the role of plankton in an estuary habitat? Give a description of these organisms
and tell why they are so important to an estuary.
8. What factors limit where and how organisms can live in an estuary? How do these
limiting factors affect the ecosystem as a whole?
9. Use the space below to draw a food chain and a food web using some of the organisms
you learned about in this activity. Include arrows in your diagram to show how the
energy flows between the organisms. Be sure to include plankton and the original source
of energy for the ecosystem.
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