Tracking Ocean Ecology with Chlorophyll A

Algae Bloom in the Baltic Sea

Image courtesy NASA

You are a member of an International Team of Marine Biologists. You are tasked with predicting and monitoring possible harmful algae blooms. Using the data maps and guiding questions, complete this challenge.
Grade Level: 4 – 6
Estimated Time for Completing Activity: One 45 minute class period
Learning Outcomes:
  • Students will observe Chlorophyll-a data from 1997-2007
  • Students will evaluate changes in the oceans chlorophyll counts from 1997-2007
  • Students will draw conclusions about how the chlorophyll-a levels in the ocean may affect its ecological characteristics
  • Students will infer areas that should be closely monitored for harmful algal blooms
  • Students will manipulate data sets from MyNASAData website
  • Knowledge of longitude and latitude
  • Knowledge of basic directional words
  • Knowledge of continent names
Lesson Links:

Chlorophyll-a is a necessary component of algae growth, and algae are at the base of the food chain. Too little chlorophyll-a will result in no growth, too much can result in explosive algae blooms which can be harmful. Drinking water must have less than 0.25 mg of algae per cubic meter, and preferably less than 0.15 mg per cubic meter

Negative Effects:

1. Dense algae will block sunlight from entering the ocean water. This will affect all of the organisms in the sunlit zone of the ocean.
The temperature of the water below the algae will decrease.
There will be a decrease in nutrients.

2. Organisms that feed on the algae may ingest harmful chemicals.
This will affect a wide range of organisms because of the food web or chain to which they belong.

3. Decrease in oxygen levels.
When the algae do die and fall to the ocean floor, it will require far more oxygen to decompose, meaning other organisms will not be able to use that oxygen.

4. Dense algae can clog gills of fish when they filter the water for oxygen to breathe.

Algae blooms also have positive effects:

1. Increase in photosynthesis means an increase in oxygen levels.
Populations near the coast while experiencing a non-harmful algae bloom will have increased productivity because of the increase of oxygen levels in the atmosphere

2. Increase in algae and phytoplankton creates more food.
Oysters, clams, mussels, humans, krill, penguins, seals, seabirds, and baleen whales eat algae and phytoplankton, and increase in the food will cause an increase in these organisms as well.

In order to study and predict algae blooms, scientists track levels of chlorophyll- a in water samples. Chlorophyll- a is an indicator of algae growth. It does not necessarily mean that algae is or is not growing or that a major bloom has occurred. They use the levels as indicators to check out what is happening in areas with higher levels. Today, the students are the scientists. They will be looking at data from 1997 through 2007 that scientists actually used. Their job will be to observe data, evaluate areas of concern, and predict further action. Keep in mind that not all algae blooms are harmful.


1. Click on the Live Access Server (Advanced Edition) Link above

2. If not automatically prompted for dataset choices, click on the ‘Choose Dataset’ button and then click on click on Oceans, and then Monthly Chlorophyll-a Concentration (SeaWiFS)

3. Make sure the time is changed to September 1997

4. Follow steps 1-9 again, but change the time to September 2007

5. A second map should appear.

6. Repeat steps 1-5 for September 2001 and 2005.

7. You should have a total of 4 open maps.

8. Respond to the prompts under Questions.


List 3 observations of change you can make based on these 4 maps. Be sure to use complete sentences and scientific language.

Identify three regions in the world’s oceans that chlorophyll concentration change with time. Be sure to use complete sentences and scientific language. Take a few moments to look over all of the graphic sources (maps)

Now the time has come to choose sites for monitoring. The problem is, your department has had major budget cuts. You are only allowed to choose one site to monitor and investigate further for potential harmful algae blooms. Using your knowledge and data, choose a site and justify your choice. You need to describe your site, and reasons for choosing it over all other choices.
Keep in mind, you must accurately describe your site using geographical, cardinal, and longitudinal and latitudinal directions. You do not want your team to show up in the wrong area.

Before looking at all of your plots, come up with a hypothesis stating how you think chlorophyll changes with its location around the world.


Zoom in on your chosen site or choose one of the following:

Look closely now, at the zoomed area. What areas have remained similar to 1997?

Using longitude and latitude, what area has changed most? How do you know?

If you could choose three sites to visit and investigate further, what two additional sites would you choose and why. Be sure to refer to the data to explain why these sites were chosen.

How do you think that algae blooms can be mitigated? Are there areas in which we would not want to mitigate algae growth?

Lesson plan contributed by Rebecca Schnekser, MY NASA DATA Team

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