Harmful Algal Blooms (HABs) and the Cayuga Lake Watershed

Last updated: October 24, 2025. Please check back as we continue to add content to this teaching module.

Introduction

This module consists of 6 sections (see outline below) with activities based on the following phenomenon and guiding question.

Phenomenon

As I was walking along the beach of Cayuga Lake one day, I came across a family looking at a sign posted by the swimming area of the lake park. The Father said “My family was planning a fun day at the beach with lots of water-related activities. Then we encountered this new sign:”

Guiding Question

Why are harmful algal blooms (HABs) happening and what can my family do so we can all get in the water again (including our pets)? 

Grade level: 6-8, 9-12

Credit and Contact Information: Mark Johnson, mjohnson71264@gmail.com

Time Required: Most sections require 3 to 4 class periods.

Matching to New York State P-12 Science Learning Standards: see details in Outline below.

Module Outline

Section 1: Energy in our lake [Download Word file, Version 1.0, Oct. 23, 2025, 1.5 MB]

1. Building a food web - Energy flow
   • Standards:

     • 5-LS2-1. Develop a model to describe the movement of matter among plants (producers), animals (consumers), decomposers, and the environment.

     • HS-LS2-3. Construct and revise an explanation based on evidence for the cycling of matter and flow of energy in ecosystems.

2. Follow the carbon
   • Standards:

     • MS-PS1-5. Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

     • HS-LS1-5. Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

3. Cellular respiration versus photosynthesis
   • Standards:

     • MS-LS1-6. Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms.

     • MS-LS1-7. Develop a model to describe how food molecules are rearranged through chemical reactions to release energy during cellular respiration and/or form new molecules that support growth as this matter moves through an organism.

Section 2: Plankton in the lake [Download Word file, Version 1.0, Oct. 23, 2025, 730 kB]

1. Collection: Plankton - what is a plankton tow?
2. Collection Equipment
   • Standards:

     • MS-ESS3-3. Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.

3. Phytoplankton vs. zooplankton
   • Standards:

     • HS-LS2-3. Construct and revise an explanation based on evidence for the cycling of matter and flow of energy in ecosystems.

Section 3: Nutrient loading - the algal bloom cascade

• Activity (pilot version): Hydro Logic Town Plan [Download Word file, Version 1.0, Oct. 23, 2025, 112 kB]

1. Nutrient sources mapping activity
   • Standards:

     • 5-PS3-1. Use models to describe that energy in animals’ food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the Sun.

     • MS-ESS3-4. Construct an argument supported by evidence for how increases in human population and per-capita consumption of natural resources impact Earth’s systems.

2. Design project: building a watershed
3. What makes the bloom happen?  Examining algal bloom formation video

Section 4: Harmful algal blooms on Cayuga Lake

1. History of harmful algal blooms –mapping activity
2. A history of climate change in New York
   • Standards:
     • ESS2-4. Use a model to describe how variations in the flow of energy into and out of Earth’s systems result in changes in climate.
3. Climate change and HABs
   • Standards:

     • MS-LS2-4. Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.

     • HS-ESS2-4. Use a model to describe how variations in the flow of energy into and out of Earth’s systems result in changes in climate.

Section 5: Harmful algal blooms and climate change

•  Activity (pilot version): Climate Change and Harmful Algal Blooms (HABs) - Data Analysis
  • [Download Word file, Version 1.0, Oct. 23, 2025, 75 kB]

1. Research activity: Why have algal blooms become more frequent?
   • Standards:

     • HS-LS2-2. Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales

2. Water quality fact sheet - What is the overall quality of our water?

Section 6: Student theories

1. Data analysis: What did you learn from sections 1 - 5?
2. Why is it dangerous for you and your pets to go swimming in our lake?
3. Where does climate change fit in?
4. What can we do individually and globally?
   • Standards:

     • MS-LS2-5. Evaluate competing design solutions for maintaining biodiversity and protecting ecosystem stability.

     • MS-ESS3-3. Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.

     • HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.

     • HS-ESS3-4. Evaluate or refine a technological solution that reduces impacts of human activities on natural systems.

     • HS-ETS1-2. Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.