tide

Salt Marsh Ecosystem: Subtidal and Supratidal Studies

by Melanie Jenkins

Objective

1. Students will learn to identify some plants and animals from the marsh ecosystem.
2. Students will learn to take abiotic data: temperature, relative humidity, wind direction, wind speed, soil & water pH, dissolved oxygen.
3. Students will learn to make observation and take down data in a quadrate study.
4. Students will learn how to do a seine pull and some subtidal organisms names.

National Science Education Standards

A. Teachers of science plan an inquiry-based science program for their students.
C. Teachers of science engage in ongoing assessment of their teaching and of student learning.
D. Teachers of science design and manage learning environments that provide students with the time, space, and resources needed for learning science.

Summary

On a coastal field trip students will study the three areas found in the salt marsh: subtidal, intertidal, and supratidal. The activities for each area are specific. The quadrate can be done in conjunction with the beach transect.

Prerequisites

Students will be introduced to the organisms they will see at the coast by videos, filmstrips, field guides, etc. in the classroom before going on a field trip.
Activity is appropriate for 8th Integrated Science, 10th Biology, high school Environmental Science. Follow-up activities and assessment will determine level.

Materials & Equipment

Salt water seine net
Water testing test kit, specifically dissolved oxygen
Soil thermometers
Sling psycrometer
Anemometer
Individual bottle of distilled water
pH meter or paper
Compass
Bucket (for carrying equipment)
Hula hoops or quadrates
Meter stick
Field guides appropriate for area

Procedure

1. Quadrate Study (Supratidal Marsh): Use hula hoops to approximate a square meter of area to be surveyed for plant and animal species. In an area to be studied lay the hula hoop over an area and have students list what they see, counting how many of each population and listing in a chart. This data can be part of a transect of the island or a separate activity.

Students can compile data later in the classroom and charts and graphs can be generated. Models can be made, and statistical analysis can be run if you wish to extend the exercise.

[NOTE TO TEACHER: hula hoops are easy for students to transport in the field and make for a good keep busy item when you only have one seine net later on...]

2. Water's Edge of the Marsh (Intertidal Marsh): Using a meter stick measure the height of the marsh snails (Periwinkles) on the cord grass (Spartina alterniflora). Have students make hypotheses about the water depth at the last tide from this data.

3. Seine Pull (Subtidal Marsh): On the back side of a barrier island in the bay or sound area find a shallow area where students can walk with the seine net for 10 - 15 meters, dragging it on the bottom slowly and tilting it back to catch as many organisms as possible. When they get back to shore keep the net at the water's edge and do not keep the organisms out of the water for too long. Put all organisms back in the water after identification. Discuss the marsh as the "nursery of the sea". Discuss the effects of pollution on the marsh. If your marsh is an estuary you can test salinity also and talk about why there are some species absent from the environment or only present in that environment. Students should list names of organisms found with approximate numbers for each seine pull. Comparisons between different places in the marsh can be done, and even graphed. Tidal pools make for great seining especially with younger students.

Assessment

Depending on the level of the class comparison papers are a good assessment. Short papers on their favorite organism and how is it adapted to the environment in which it lives or longer papers comparing and contrasting different areas within the marsh subtidal with supratidal and how cord grass is different from black needle rush for example. If you can get a permit to collect or your area is not in a state park, plant collections by students are nice. You can have them make the identification tags very specific with as much phylogenetic information as you think they can find, but be reasonable; sometimes there is only one book with classes keyed out in the whole town! Photo collections are terrific also. This is only limited by your imagination. :)

Extension

Link to Maritime Forest and Beach activities and do as a whole unit on Coastal Ecology. You can actually teach all basic ecology objectives at the coast. What are the effects of sea-level rise on coasts? Have students brainstorm what happens to the subtidal organisms when more water is added to the ecosystem (Can sunlight penetrate the water and get to the plants living under the water's surface as well with deeper water? As abiotic data changes, does dissolved oxygen content remain the same? Why would this matter? )? Supratidal organisms drown when sea-level rises on coasts; is this a problem? Can we ever risk losing a single species from the environment?

Resources

photo by Melanie Jenkins at Cape May, NJ 7-18-98
lab by Melanie Jenkins
use field guides appropriate to your area

Woodrow Wilson Leadership Program in Environmental Science

lpt@www.woodrow.org
The Woodrow Wilson National Fellowship Foundation

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CN 5281, Princeton NJ 08543-5281

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