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Oregon Coast Ecosystem Model

Kelp Forest Balance

Investigate how sea otters, sea urchins, kelp growth, ocean warming, and storms can reshape a coastal ecosystem over thirty years.

Life Science Grades 7–12 15–30 minutes No login required
1

Choose a starting system

Scenario presets

Start with a preset, then change one variable at a time for a fair investigation.

3

Observe

Oregon coastal kelp forest

Year 0
Healthy starting conditions
Ambient motion reflects currents, storms, and habitat
Sea otters 12 Starting population
Sea urchins 75 Starting population
Kelp coverage 72%
Habitat health 78 Fish habitat: Strong
Run the model to observe how a trophic cascade changes the kelp forest.
4

Analyze and compare

Thirty-year ecosystem evidence

Kelp cover Urchins Otters
Year 0 of 30

Saved runs

Save up to three trials, then turn on Compare Runs.

No trials saved yet.

Suggested investigation

How does sea otter abundance affect kelp forest stability?

  1. Predict: What will happen if the starting otter population decreases?
  2. Test: Keep every variable constant except starting sea otters.
  3. Compare: Save at least three 30-year trials.
  4. Explain: Describe how changes move from otters to urchins to kelp.
  5. Critique: Identify one real-world factor that this model simplifies.

Evidence prompts

Build a scientific explanation

Claim: Which conditions produced the healthiest long-term kelp forest?

Evidence: Cite at least two values and one pattern from the graph.

Reasoning: Explain the trophic cascade connecting otters, urchins, and kelp.

How the model works

A simplified trophic cascade

Sea otters reduce sea urchin abundance through predation. Sea urchins graze on kelp. Kelp provides structure and habitat, so changes at the top of the food web can affect the wider ecosystem.

Ocean warming lowers kelp growth and recovery. Storm pressure removes kelp directly. Otter protection changes long-term otter survival.

Model limitations

What is left out?

  • All otters, urchins, and kelp are treated as identical.
  • Disease, migration, fisheries, currents, and genetics are simplified or omitted.
  • The habitat is represented as one connected kelp forest.
  • The model demonstrates possible patterns; it does not predict a real Oregon population.

NGSS connections

Designed for systems thinking

  • MS-LS2-1: Resource availability and population change
  • MS-LS2-2: Patterns of interactions among organisms
  • MS-LS2-4: Evidence about ecosystem change
  • HS-LS2-1: Computational representations of carrying capacity
  • Crosscutting concepts: Cause and effect; stability and change; systems and system models