Material adapted from: Estuaries: Interface between sea and land & Sea Margin Diversity, The Water Sourcebook Grades 9-12, EPA http://www.epa.gov/safewater/kids/wsb/ Introduction: Some of the most dynamic areas on Earth are found at the interface of land and sea, especially in areas we know as estuaries. Estuaries can be defined as a semi-enclosed body of water which has a free connection to the open sea and within which seawater is measurably diluted by fresh water derived from land drainage. They are coastal zones (such as bays, lagoons, sounds or sloughs) where freshwater systems/rivers meet and mix with the salty ocean, becoming brackish. In this activity, students will be introduced to the structure of estuarine systems and their formation through modeling and mapping. Objectives: Students will be able to: Identify different coastal regions across Oregon and the U.S. Describe the five different types of estuary structure Describe the function of estuaries in both watersheds and coastal ecosystems Identify where different estuaries are located in Oregon and the U.S. Explain the value of estuaries in maintaining the integrity of natural ecosystems State the impact human use and misuse has on estuaries. Ocean Literacy Principles These activities support: Essential Principle # 5 the ocean supports a great diversity of life and ecosystems Essential Principle # 6 the oceans and humans are inextricably interconnected. Materials: Modeling clay (see recipe below for a biodegradable version) Petri dishes or plastic plates Food coloring Ice trays Hairdryers or heat lamps (optional) Wall map of Oregon Wall map of the United States 5 different colored push pins (Materials in bold are provided by SMILE) Materials provided are enough to support 20 students
Handouts/Transparencies: Handout A: Coastal Margins Coastal Margins Transparency Transparencies of Estuary Structures Handout B: Estuary Descriptions Handout C: Estuary Diagram Estuary Transparency Modeling Clay Recipe Set-Up 1. Freeze water colored with food coloring in the ice trays. Part A: Mapping 1. Display the coastal margins transparency. Discuss different types of coastal margins and how these may impact us either directly or indirectly (e.g. if student has eaten seafood, what region did this food source originate from?). Have students follow along with Handout A. 2. Divide students into small groups. Provide each group with different color map pins and have each group attempt to estimate locations of one of the following types of coastal regions on both the Oregon and U.S. map: a. Bay b. Delta c. Estuary d. Fjord e. Sound f. Lagoon g. Gulf Have each group report back how they decided on these locations. Map features? Common knowledge? Did the groups locate more accurately on a state level or on a national level? Part B: Modeling 1. Introduce estuaries, their key function and explain the different types of estuary structure, using the transparencies to help. Brainstorm with the students the key identifying features of estuaries in general. 2. Divide the students into small groups. Provide each group with one of the five estuary descriptions from handout B. Hand out clay and petri dishes/plates and, using their description, have each group construct a coastline with various raised areas corresponding to their estuary structure inside the dish. 3. Provide each group with 3 cubes of colored ice and let them place the ice on their clay model. As the ice melts, have the students note down how the water fills in
their model, does this correlate with the formation of this particular estuary structure? Using a hairdryer or heat lamp can speed up the ice melt. Alternatively, these observations could be completed whilst students participate in next part of the class. 4. Display the estuary transparency. Identify and discuss the smaller habitats found in this environment. Have students follow along with handout C. 5. Have each group brainstorm a list of ways estuaries may be so important to marine life and to humans, reporting back to the rest of the class. 6. Using their remaining map pins, ask each group to try and identify examples of their assigned estuary structure on the maps. What features on each map may provide a clue? Students may use the examples identified in the descriptions to help. Wrap Up Summary questions: 1. What types of coastal regions exist? Are there any good local or state examples? 2. What is an estuary? How are they formed? 3. Where might we find different structures of estuaries? Extensions: 1. Discuss how many estuaries have been damaged or heavily impacted by human activity. Talk about value, natural stresses, necessity to humans and restoration. Have each group brainstorm how we can reduce these impacts and create a poster advertising this idea to the public. 2. In groups (determined by number of habitat models being built), have the students make modeling clay by mixing 2 parts flour to 1 part salt with water and vegetable oil. Use the to mold a model that depicts a river, marsh or estuary habitat. The habitat is placed in one section of plywood (~4 x 4 ) form so that it fits beside others creating an entire watershed or coastal region. Straw, astroturf, plastic plants, and wire can be used at students discretion to make realistic features. Areas under water may be painted blue while land features may be painted brown. The finished product should reinforce the concepts of watershed and coastal habitat studies. Vocabulary: Bar-built estuary Type of estuary formed by a series of bars or islands created from offshore depositing
sand, washed down by rivers or in from deep water. The sand walks up the continental shelf and stabilizes. A bar-built estuary is usually laterally extended along the shore, and is long, narrow, and low. Bay A body of water partly enclosed by land but with a wide outlet to the sea. Benthic Living on the bottom of a lake or sea; pertaining to the ocean bottom Bioaccumulation To accumulate larger and larger amounts of a toxin within the tissues of organisms in each successive trophic level. Biological magnification (biomagnification) Bioaccumulation occurring through several levels of a food chain; process by which certain substances (such as pesticides or heavy metals) are deposited into a waterway, are eaten by aquatic organisms which are in turn eaten by large birds, animals, or humans, and become concentrated in tissues or internal organs as they move up the food chain. Biotic Living or derived from living things. Channelization The straightening and sometimes deepening of stream or river channels to speed water flow and reduce flooding. A waterway so treated is said to be channelized. However, channelization can cause unstable situations and may cause adverse environmental impacts. Delta A deposit of sand and soil, usually triangular, formed at the mouth of some rivers. Deltaic estuary Type of estuary formed by a delta. Detritus Decomposed or disintegrated organic matter (found in water and on land), and associated microbial elements. Distributary A branch of a river that flows away from the main stream. Drowned river valley Type of estuary that is wider than deep and triangular in shape Emergent Rising from a surrounding liquid. Estuary
A marine ecosystem where freshwater enters the ocean. The term usually describes regions near the mouths of rivers, and includes bays, lagoons, sounds, and marshes. Fjord Narrow, deep valleys carved by glaciers and flooded by the sea. Fjord-drowned glacial valley Type of estuary usually found in arctic and polar regions. They are U-shaped, deeper than wide, and have a small river discharge and large tidal volume; important to shipping. Fluvial Found in, produced by, or relating to a river. Gulf A large area of sea or ocean partially enclosed by land. Interstitial Of, forming, or occurring in a small or narrow space between things or parts. Intertidal Of, or pertaining to a shore zone bounded by the levels of low and high tide. Lagoon A shallow body of water, especially one separated from the sea by sandbars or coral reefs. Leeward In the direction toward which the wind blows; of the side of anything away from the wind. Levee An embankment, natural or artificial, built alongside a river to limit high water events from flooding bordering land. Mangrove swamps Tropical, wet, coastal areas dominated by mangroves (trees). Mangroves have extensive root systems, which form a dense thicket, providing cover for aquatic life. Mud flats Large estuarine expanses composed of rich mud exposed at low tides. Salt marsh Estuarine habitat submerged at high tide, but protected from direct wave action, and overgrown by salt-tolerant herbaceous vegetation; aquatic grasslands (coastal prairies) affected by changing tides, temperatures, and salinity. Sound Long, broad inlet of the ocean larger than a strait or channel, connecting larger bodies of water.
Strait A narrow passage that connects two larger bodies of water. Tectonic estuary Type of estuary formed when the Earth s crust shifts suddenly as in an earthquake, volcanic eruption, or a tsunami; has no definite shape. Tidal creeks Meandering creek-like channels within salt marshes and mud flats, through which seawater enters and leaves as the tide rises and falls. Tidal flats Flat-topped banks of sand and silt that comprise the most elevated portion of the salt marsh Tsunami A huge sea wave caused by a submarine disturbance such as an earthquake or volcanic eruption
Handout A Coastal Margins
Coastal Margins
Estuaries: Handout B - Estuary Descriptions (1) COASTAL PLAIN (DROWNED RIVER VALLEY) The classic estuary, wider than deep and triangular in shape, consisting of marshes, mudflats and tidal creeks. Created millions of years ago as ancient glaciers melted, causing rising sea levels that drowned coastal streams and river valleys. Examples include Chesapeake, Delaware, Savannah, Hudson and Columbia River Estuary, OR. (2) FJORD (DROWNED GLACIAL VALLEY) Usually in Arctic or Polar Regions, these are u-shaped, deeper than wide and have a small river discharge with a large tidal volume, hence they are important to shipping. An advancing glacier erodes out long, narrow valleys with steep sides, and when the glacier melts, seawater floods into the remnant valley. Examples are in Puget Sound, WA, Valdez, AK, New Zealand and Norway. (3) DELTAIC The most changeable estuary structure consisting of fluvial depositions with a large river discharge. They form at the mouth of large rivers from sediment and silt deposition, often when river flow is restricted by the river delta itself. They are very prone to the influence of waves, tides, longshore currents, storm damage and sediment lay down. Examples include on the Mississippi River, Amazon River and Nile River. (4) BAR-BUILT The most dynamic of estuary structures, a series of bars or islands created from offshore deposition of sand, washed down by rivers or from deep water, creates a protected area fed by small streams. Bar-built estuaries, usually laterally extended along the shore, are long, narrow and low-lying, such as near sand spits or barrier islands. Some have such low river flow in summer they become blind estuaries an offshore sand bar size increasing so much it closes off the mouth of the estuary (e.g. Sixes River, OR). Bar-built estuaries exist on the leeward side of the river, changing quickly with oceanic movements. Examples include the Mississippi Sound, Cape Cod, Long Island and Salmon River, OR. (5) TECTONIC These estuaries form when the Earth s crust shifts suddenly such as during an earthquake, volcanic eruption, or a tsunami. The shift creates a large land sink in the Earth below sea level, which subsequently fills with water. Tectonic estuaries have no definite shape. A good example is San Francisco Bay.
Coastal Plain http://www.ozcoasts.org.au Fjord http://www.britannica.com
Deltaic http://www.coastalresearch.nl Bar-Built http://www.cnsm.csulb.edu
Tectonic http://dcm2.enr.state.nc.us
Handout C Estuary
Estuary
Modeling Clay Recipe Taken from www.moonsweb.com Ingredients: 2 Cups Plain Flour 1 Cup Salt 1 to 1½ Cups water 2 Tbsp Vegetable/Mineral Oil Food coloring (optional) Makes about 2 cups of dough Directions: 1. In a mixing bowl, stir together flour and salt. Add food coloring if desired. 2. Gradually add water and oil until mixture becomes a dough-like consistency. Add more water/flour if mixture is too dry/wet. 3. Knead the dough well until it forms a soft ball. 4. Dough can be air-dried or baked in the oven at 300 F until hard.