Eyes on the Estuaries

Monitoring Estuaries / 9-12 / Life Science, Earth Science

Focus Question

How can we monitor and compare living resources in U.S. estuaries?

Learning Objectives

Links to Overview Essays and Resources Useful for Student Research



Audio/Visual Materials


Teaching Time

One or two 45-minute class periods, plus time for student research.

Seating Arrangement

Groups of 3-4 students

Maximum Number of Students


Key Words



Background Information

Coastal ecosystems provide many benefits to human communities, including food, ports, recreational opportunities, habitats for diverse plant and animal life, and minerals. More than half of the U.S. population lives near a coast, and about one of every six jobs in the U.S. is related to coastal or marine resources. Because these systems are vulnerable to stress from natural processes and human activity, NOAA's National Ocean Service (NOS) has a variety of programs designed to protect coastal resources and the opportunities they provide. Two of the basic requirements for providing this protection are:

Coastal monitoring programs provide the information needed to recognize and interpret changes in coastal resources.

“Coastal monitoring” refers to periodic measurements of physical, chemical, biological, and meteorological factors that may affect the use and quality of coastal resources. For example, such factors may include temperature, salinity, presence of chemical contaminants, biological species, life stages of these species (eggs, juveniles, adults, etc.), rainfall, and storm events. NOS supports 28 different monitoring systems to provide key pieces of information needed to protect marine resources and control the ways in which they are used. These programs fall into four classes that represent different geographic scales.

The first class includes measurements of environmental features over large geographic areas using sensors or instruments on airplanes, satellites, and ships. These features include distribution of habitat types or land cover, algal blooms, water depth, shoreline location, and land topography.

The second class includes physical, chemical, biological, and meteorological measurements at specific sites. These measurements are made periodically and are usually intended to provide information on specific resources or environmental stresses. Measurements include currents, water quality and weather in 26 National Estuarine Research Reserves, contaminants in sediments and bivalve molluscs at 250 sites, and water level measurements used to predict tides.

The third class includes intensive and frequent measurements of environmental conditions at a few locations of particular importance. These include coral reef ecosystems, 13 National Marine Sanctuaries, sites where there is a high potential for substantial environmental degradation (Narragansett Bay, Chesapeake Bay, and San Francisco Bay are among more than 280 sites being monitored) and real-time measurements of water levels, currents, and other oceanographic conditions in 10 U.S. ports including New York/New Jersey Harbor, Houston/Galveston Bay, Los Angeles/Long Beach, and the Port of Anchorage.

The fourth class includes monitoring activities that are focussed on a single physical location, ecosystem, or oil spill sites. The Everglades, Chesapeake Bay, and the M/V Selendang Ayu oil spill site in Alaska are among the areas included in this part of the NOS monitoring program.

This activity focuses on information contained in the NOS Estuarine Living Marine Resources (ELMR) Database. The ELMR Program was established to develop baseline information on ecologically and economically important fishes and invertebrates in U.S. estuaries. The database includes information on the distribution, relative abundance, and life history characteristics of 153 species found in 122 estuaries and coastal embayments on the Pacific, Atlantic, and Gulf of Mexico coasts. In this lesson, students will use the ELMR Database to compare characteristics of selected species in two or more estuaries, and to draw inferences about the ecology of these estuaries.


Learning Procedure

Part 1

  1. Decide which estuaries and which species within these estuaries will be assigned to each student group. If the same estuaries and species are assigned to each group, it will be easier for students to compare their results with those of other groups. On the other hand, assigning each group a different set of estuaries and species will provide greater variety, as well as ensure that each group does their own work; but this will also require more advance preparation by the teacher.
  2. The key consideration is that the assigned species must be present in both assigned estuaries to permit comparison between the two sites. If the assigned estuaries are from different regions (Mid-Atlantic, South Atlantic, etc.) there is greater likelihood that there will be noticeable differences in the ecological characteristics of at least some of the species found in both locations. The best way to make these decisions is to visit the ELMR Database at http://www8.nos.noaa.gov/biogeo_public/elmr.aspx , and scan through the data for estuaries that you think may be suitable to get an idea of the species for which data are available. You may want to include one or two invertebrate species as well as fishes for each student group. For example, the following species are among those that could be compared in the Winyah Bay and Chesapeake Bay estuaries:

    American Eel
    American Shad
    Atlantic Croaker
    Atlantic Menhaden
    Atlantic Sturgeon
    Bay Anchovy
    Black Drum
    Blue Crab
    Brown Shrimp
    Daggerblade Grass Shrimp
    Eastern Oyster
    Red Drum
    Summer Flounder

  3. Discuss the importance of living estuarine resources and some of the sources of stress that may threaten these resources. Students should realize that stress may result from natural processes (such as storms, drought, or disease) as well as human activity such as coastal development, heavy industry, or oil spills. Be sure students understand that many organisms are adapted to withstand natural stresses, but may not be able to tolerate these stresses if they are also exposed to stress from human activities. Discuss the importance of being able to recognize change in populations of estuarine organisms and of being able to separate normal variability from unusual change. Both of these capabilities depend upon having “baseline” information about species of interest that can be compared with new information from periodic monitoring of these species.
  4. Tell students that their assignment is to prepare a written report in which they summarize baseline information about selected species in two (or more) estuaries, and use this information to draw inferences about the ecology of these species. Be sure students understand that the primary purpose of the ELMR Database is to provide a reference point for each estuary that can be used to analyze future monitoring data from the SAME estuary. These reference data, though, can also provide information about variations in the life history of individual species in different estuaries.

  5. Assign each student group at least three species in at least two different estuaries, and provide each group with a copy of the “ELMR Database Student Worksheet" found at the end of this lesson plan. Click here for a separate printable worksheet.

  6. Have each student group present an oral summary of their analyses and inferences based on steps 6 and 7 on the Worksheet. Students should understand that a defining characteristic of all estuaries is variable salinity, and that this characteristic can offer advantages to species that can tolerate a range of salinities. At a minimum, student analyses should accurately summarize abundance data for each of the five life stages, as well as the salinity ranges in which these stages were found. Inferences should include ideas about how these data may reflect reproductive strategies.

    In a discussion of the Winyah Bay alewife data, for example, students should recognize that this species spawns throughout the spring, so eggs and spawning adults are most common during March, April, and May. As the eggs develop, larvae appear and are abundant through June. Juveniles appear somewhat later and remain abundant through November. Students may infer that eggs and larvae do not tolerate salinities above 0.5 ppt, or may hypothesize that these life stages inhabit low-salinity waters to avoid predators that require higher salinities. The latter hypothesis is supported by the observation that spawning adults were found only in waters with salinity of 0 - 0.5 ppt, even though non-spawning adults were equally abundant in all three salinity ranges. In addition, juveniles appear to expand their salinity range as they grow older. The absence of any life stages during December through February may suggest that alewife use estuaries primarily as spawning and nursery areas, and live in farther from shore during the winter months.

    Severe storms or prolonged droughts may alter the salinity distribution within an estuary. Reductions in freshwater flow caused by droughts or seawater driven into estuaries by storm winds could both cause higher-than-normal salinities. This could be fatal for life stages of species that are confined to low salinity waters (such as the eggs, larvae, and young juveniles of alewife).

    These patterns will vary, depending upon the estuary and species. White shrimp adults and juveniles, for example, are found in the Winyah Bay estuary throughout the year, though larvae of this species are only present from May through September. No eggs or spawning adults of this species were observed in any month, which might mean that spawning occurs elsewhere or more likely that these stages were missed by the sampling program that produced the data.


The Bridge Connection

The Bridge is a growing collection online marine education resources. It provides educators with a convenient source of useful information on global, national, and regional marine science topics. Educators and scientists review sites selected for the Bridge to insure that they are accurate and current.

www.vims.edu/bridge - Click on “Ocean Science Topics” in the navigation menu to the left, then “Habitats,” then “Coastal,” then “Estuary” for links to resources about estuaries.

The “Me” Connection

Have students write a brief essay describing a monitoring program for an ecosystem in their own community that is personally important. Essays should include an explanation of why this system is important (reasons could include ecological, economic, or aesthetic values, or a combination of these), what factors would be monitored, and how frequently monitoring should be done.


Visit http://www.epa.gov/owow/estuaries/monitor/ for an online manual for Volunteer Estuary Monitoring, as well as information on the ecology of estuaries and how they are threatened.



http://www.epa.gov/owow/estuaries/kids/ – Games and activities about estuaries produced through the National Estuary Program.

http://www.northinlet.sc.edu/estnetweb/estnet.html – “Estuary-Net Project;” an online project to develop collaborations among high schools, community volunteer water quality monitoring groups, local officials, state Coastal Zone Management (CZM)  programs and National Estuarine Research Reserves  (NERRS) to help solve non-point source pollution problems in estuaries and their watersheds.

National Science Education Standards

Content Standard A: Science as Inquiry

Content Standard C: Life Science

Content Standard F: Science in Personal and Social Perspectives


Ocean Literacy Essential Principles and Fundamental Concepts

Essential Principle 5. The ocean supports a great diversity of life and ecosystems.

Essential Principle 6. The ocean and humans are inextricably interconnected.

Essential Principle 7. The ocean is largely unexplored.


Eyes on the Estuaries

ELMR Data Base Student Worksheet

The ELMR Data Base includes data on selected fish and invertebrate species in 122 estuaries along the coastlines of the United States. Each estuary is divided into one to five salinity zones. In each zone, data are provided for the relative abundance of five life stages for each of the selected species that are present. These life stages are adults, eggs, juveniles, larvae, and spawning adults. Data for each life stage for each species are provided for each of twelve months. Relative abundance is represented by a scale from 0 to 5:

0 = not present
2 = rare
3 = common
4 = abundant
5 = highly abundant
An entry of “.” means that no data are available.

Your assignment is to compare data for certain species in two or more estuaries assigned by your teacher. For each assigned species, you should find out:

  1. Open the ELMR Data Base at: http://www8.nos.noaa.gov/biogeo_public/elmr.aspx/.

  2. Select the “Region” that includes the estuary you are interested in (SOUTHEAST), then the appropriate estuary name in the “Estuary” window (WINYAH BAY). You can confine your search to specific Species, Life Stages, and Salinity Zones, or just leave “All” selected in these windows. For     now, leave “All” selected. Click the “Save As Text” button. The file will be saved onto your hard drive as a “zip” archive.

  3. Unzip the downloaded data file, and open the ELMR download text file in Microsoft Excel®. You will get the Text Import Wizard
    Step 1. Select “Delimited,” “Start Import at Row: 1,” and the operating system you are using next to “File Origin.” Click “Next.”
    Step 2. Select “Delimiters: Tab” and “Text Qualifier: “ Click “Next.”
    Step 3. Click the “General” button under “Column Data Format.” Click “Finish.”

  4. You now have a spreadsheet with all of the data for Winyah Bay. Now, you need to make a few adjustments to this spreadsheet to make it easier to analyze:
    • Highlight columns B and C. Under the “Format” menu, select “Column” and then “Width.” Change the width of columns B and C to 2 inches.
    • Highlight columns E through P. Under the “Format” menu, select “Column” and then “Width.” Change the width of columns E through P to 0.5 inch.
    • Highlight all cells by clicking on the empty cell in the upper left corner. Under the “Data” menu click “Sort.” Check the box next to “Header Row” under “My list has.” Under “Sort By” select “Common Name.” Under “Then by” select “LifeStage.” Click “OK.
  5. Prepare data summary graphs for each of your assigned species as follows:
    • Highlight all cells in columns C through P for all Life Stages of the species you are analyzing. For this example, suppose “Alewife” is one of your assigned species; so you would highlight cells C2 through P16
    • Click on the Chart Wizard icon. Select “Column” under “Chart type” and the upper left icon under “Chart subtype.” Click “Next.”
    • Click the button next to “Rows” under “Series in.” Click the “Series” tab, and remove all life stages except “Adults” and “Spawning.” Click “Next.”
    • Click the “Titles” tab. Enter a title for your chart (such as “Alewife Adults and Spawning”). Enter “Month” in the “Category (X) axis:” box and “Abundance” in the “Value (Y) axis:” box. Click “Next.”
    • Click the button next to “As new sheet” and enter the name that you want to appear on the tab for your chart in the spreadsheet workspace. Click “Finish.” You now have a column chart that shows the relative abundance of alewife adults, and spawning adults in each salinity zone for each month.
    • If you want to print your chart and do not have a color printer, you may want to change the column fills to black and white patterns. To do this, double click on one of the columns on your chart. The “Format Data Series” dialogue box will open. Click on the “Colors an Lines” tab, then select “Fill Effects . . . “ from the Color drop down menu, then click the “Pattern” tab. Select black in the window under “Foreground:” and white in the window under “Background:” Select the pattern you want, then click “OK.” Click “OK” in the “Format Data Series” dialogue box.
    • The column on your chart should now contain a black-and-white fill pattern. Repeat these steps for the other columns.
    • Repeat steps a. and b. Click the button next to “Rows” under “Series in.” Click the “Series” tab, and remove “Adults” and “Spawning” life stages. Click “Next,” and repeat steps d. and e. You now have a second column chart that shows the relative abundance of alewife eggs, larvae, and juveniles in each salinity zone for each month. Adjust the column fills if necessary.
  6. Use your chart to find out:

    • When are spawning adults most abundant?
    • When are eggs most abundant?
    • When are larvae most abundant?
    • When are juveniles most abundant?
    • When are adults most abundant?
    • Are any of these life stages more abundant in certain salinity zones?

    For the Winyah Bay alewife example, adults and spawning adults are most abundant in March, April and May; eggs are most abundant in March, April and May; larvae are most abundant in March, April, May and June; juveniles are abundant from April through November. Notice that all life stages of alewife are absent from December through February. Different life stages of alewife appear to have different salinity preferences. Alewife eggs and larvae are found only in salinities of 0 - 0.5 ppt. Juveniles are also confined to this salinity zone during April, May, June, and July; but are found in the 0.5 - 25 ppt salinity zone between August and November, and in the > 25 ppt zone between September and November. Alewife adults are found in all three salinity zones, but spawning adults are only found in the 0 - 0.5 ppt zone.

  7. Discuss possible reasons for seasonal variations in the abundance of different life stages. What effect could severe storms or prolonged drought have on your assigned species?


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