Investigating the Long Island Sound Lobster Collapse

Overview

In this task, you will investigate the environmental factors that led to the dramatic decline of the American Lobster population in the Long Island Sound during the late 1990s. Using an interactive simulation, you will manipulate variables such as fishing pressure, nitrogen runoff, and an unknown environmental variable (“Mystery Variable X”) to understand how these factors interact to maintain a stable ecosystem—or push it into collapse.

Estimated Time: 45-60 minutes Materials: Computer with internet access, Long Island Sound Lobster Collapse Simulation

1. Engage

Read the following scenario and consider the phenomenon:

In the late 1990s, the American Lobster (Homarus americanus) population in the Long Island Sound suffered a catastrophic die-off. Lobstermen who had fished these waters for generations pulled up traps full of dead or dying lobsters. The collapse was swift and severe, devastating the local fishing industry and permanently altering the benthic (bottom-dwelling) ecosystem. What caused this sudden and extreme change?

Class Discussion:

• What factors do you think could cause a sudden die-off of a marine population?
• How might human activities contribute to changes in an aquatic ecosystem?

2. Explore

Open the Long Island Sound Lobster Collapse Simulation.

Familiarize yourself with the controls:

• Fishing Pressure: Adjusts the commercial harvesting rate.
• Nitrogen Runoff: Simulates fertilizer and sewage entering the sound, which fuels algal blooms.
• Mystery Variable X: An unknown, changing abiotic factor in the bottom waters.

Initial Investigation:

1. Keep all variables at their default settings (Fishing Pressure: 20%, Nitrogen Runoff: 10%, Mystery Variable X: 20%). Click “Play”.
2. Observe the “Ecosystem Status” readout for Lobster Population and Dissolved Oxygen over 50 time steps.
3. Pause the simulation. Record your observations. Was the ecosystem stable?

3. Explain

Now, test each variable independently to determine its effect on the ecosystem. For each trial, press “Reset”, adjust the target variable as instructed, and leave the others at their defaults. Run the simulation for 100 time steps and record the final state.

Data Collection Table

Analysis Questions:

1. Did high fishing pressure alone cause a total collapse of the lobster population? Explain based on your data. _____

2. How did high nitrogen runoff affect the dissolved oxygen in the water? What biological process causes this (Hint: think about algal blooms and decomposition)? _____

3. What do you think “Mystery Variable X” represents? How does it interact with the other variables? _____

4. Elaborate

Based on your findings, construct a scientific explanation for the lobster collapse.

Your deliverable: Write a short argument (1-2 paragraphs) claiming what caused the Long Island Sound lobster collapse.

• State your claim clearly.
• Provide quantitative evidence from the simulation (data from Trial 4 compared to Trials 1-3).
• Provide reasoning that connects the evidence to the claim, explaining how the combination of variables (complex interactions) disrupted the ecosystem’s stability, leading to a new, altered state.

5. Evaluate (Extension)

Research the actual events of the 1999 Long Island Sound lobster die-off.

• Identify the real-world equivalent of “Mystery Variable X” (e.g., bottom water temperature increases due to climate change).
• Evaluate your simulation findings against historical data. Did the simulation accurately model the complex interactions that maintain or disrupt ecosystem stability?

Teacher Notes: NGSS Alignment

This task aligns with the following Next Generation Science Standards:

Performance Expectation:

• HS-LS2-6: Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.

Dimensions:

• SEP: Engaging in Argument from Evidence: Students construct and evaluate an argument using simulation data to explain the lobster collapse.
• DCI: LS2.C: Ecosystem Dynamics, Functioning, and Resilience: Students observe that modest disturbances (e.g., moderate fishing) maintain stability, while extreme fluctuations (combined nitrogen runoff and temperature stress) challenge ecosystem functioning, leading to a population crash.
• CCC: Stability and Change: Students investigate how changing specific variables disrupts the stability of the benthic ecosystem.

Evidence Statements Addressed:

• 1. Identifying the given explanation and the supporting claims, evidence, and reasoning: Students identify the explanation that combined environmental stressors (nitrogen and temperature) caused the collapse, rather than fishing pressure alone.
• 2. Identifying any potential additional evidence: Students identify factors affecting biodiversity and species relationships.
• 3. Evaluating and critiquing: Students assess the strengths and weaknesses of different claims (e.g., fishing vs. environmental factors) based on simulation data showing the response of the population to changing conditions.
• 4. Reasoning and synthesis: Students synthesize data from multiple trials to reason how the combination of variables pushes the ecosystem beyond its resilience threshold, resulting in a new ecosystem state.