Ecosystem dynamics in the salt marsh
Standards
B-6.1 Explain how the interrelationships among organisms (including predation,
competition, parasitism, mutualism, and commensalism) generate stability within
ecosystems.
Performance Objectives
 Students will construct micro-ecosystems in plastic containers/soda bottles
 Students will maintain and track changes in population, plant growth, water
quality, and animal growth over a four week period
 Students will graph and interpret data
Materials
Plastic containers/ bottles
Marsh sediment/mud
Spartina alterniflora (cordgrass) plants
Tidal creek water
Snails
Crabs
Other biota found in the marsh
Hook
Before class activity the students will go to the salt marsh to explore the ecosystem and
collect materials for bottle biome. They will identify populations and communities and
determine characteristics that make up a stable ecosystem.
Concept Exploration
Instructions
1. Cut the top off one bottle, at the shoulder (where it tapers). Cut the base off
another bottle and score it with holes. This is the cover.
2. Add several oyster shells to the bottom of the bottle.
3. Place 2 inches of sediment in the bottom of the container
4. Anchor Spartina (or other plants) in sediment
5. Fill container with salt water
6. Add snails, crabs or other salt marsh organisms
7. Decide where you should place your ecosystem within the room (Think about the
basic needs of the organisms in your ecosystem.)
8. Data will be collected over four weeks on population, plant growth, water quality,
and animal growth
9. Once the data is collected, graph data to help identify what is happening in the
ecosystem
Concept Introduction
The Teacher will ask the students to describe what has happened in the bottle ecosystems
and ask for the students to come up with plausible explanations for what they see.
Then the teacher will introduce the concepts of
 ecosystem – a community (all the organisms in a given area) and the abiotic
factors (such as water, soil, or climate) that affect them.
 stable ecosystem - population numbers of each organism and the supply of
resources in the physical environment fluctuate at a predictable rate; energy flows
through the ecosystem at a fairly constant rate over time.
 Interactions between organisms
o Predation - an interaction between species in which one species (the
predator) eats the other (the prey).
o Competition - a relationship that occurs when two or more organisms need
the same resource at the same time.
o Parasitism - a symbiotic relationship in which one organism (the parasite)
benefits at the expense of the other organism (the host). In general, the
parasite does not kill the host.
o Mutualism - a symbiotic relationship in which both organisms benefit.
Because the two organisms work closely together, they help each other
survive
o Commensalism is a symbiotic relationship in which one organism benefits
and the organism is not affected.
Concept Application
The students will graph their results and identify what relationships where displayed by
the bottle.