Phytoplankton in the Gulf of Maine

Gulf of Maine ocean productivity

Image courtesy Visible Earth – MODIS

To use satellite data to explore and determine the correlation between sea surface temperature, sunlight, and the amount of chlorophyll (phytoplankton) in the Gulf of Maine at various times of year
Grade Level: 7 – 8
Estimated Time for Completing Activity: 50 minutes
Learning Outcomes:
  • Students will be able to use satellite data to identify differences in chlorophyll concentration.
  • Students will be able to use Excel to examine and analyze remotely- sensed data to identify conditions that may lead to a plankton bloom.
  • Introduction to Phytoplankton
  • Familiarity with using the Internet to access websites
  • Experience using Excel to import data and make charts
  • Computer with Internet access
  • Excel or other Spreadsheet software
  • Color Printer and Paper
AP Environmental Science Topics
Lesson Links:

Phytoplankton, microscopic floating plant-like marine organisms (plankton means wanderer) are at the bottom of the marine food chain. They perform photosynthesis using water, carbon dioxide, and sunlight to produce glucose for their own use, as well as oxygen. Humans and all land animals and sea creatures are dependent on phytoplankton. Oceanic phytoplankton produce more oxygen than all the land plants and trees on Earth. Plankton blooms occur each year in the spring and fall in the Gulf of Maine.

During the summer, the warm surface layer of ocean water floats on top of cold, dense water. Nutrients are trapped in the thermocline, due to a lack of mixing between layers with very different densities, acting as a barrier between the two layers. When the surface water cools and becomes more dense in the winter, the thermocline disappears and through wind and wave action, nutrients are brought to the surface. The combination of adequate nutrients and lengthening daylight in the spring contribute to a plankton bloom. The North Atlantic spring plankton bloom is the largest in the world. As the water warms and the thermocline develops in the summer, the lack of nutrients at the surface causes the plankton to die off. As nutrients become available in the fall, there is another, smaller plankton bloom which is limited by the amount of sunlight available.

The chlorophyll in phytoplankton can be observed by remote sensing instruments and is used by scientists as a measure of phytoplankton.


Part I: Overview of the seasonal cycle in the Gulf of Maine

1. Print or save color plots showing chlorophyll concentrations in the Gulf of Maine in January, April, July, and October of any single year.

To do this, Click on the Lesson Link for LAS Advanced Edition.
Follow LAS links to parameter: Oceans, Monthly Chlorophyll-a Concentration

Change the latitude and longitude coordinates to: 72W-65W, 40-44N
change your date: Enter Month and Year
Click the ‘Update Plot’ radio button to see your changes.

2. Also print or save your color plots of sea surface temperature and sunlight data for the same months using links to the parameters:

Go back to the Live Access Server as above and click on:
Atmosphere, Atmospheric Radiation, Surface, Monthly Surface All-sky SW Downward Flux
Oceans, Weekly Sea Surface Temperature

3. Divide into small groups of three or four, each with a set of the color plots. Work together to answer 1-3 of the Lesson Questions below.

Part II: Examine the annual cycle at a certain location in the Gulf of Maine and determine correlations

1. Return to the LAS to make line plots of the same data parameters for one particular location in the Gulf of Maine for the full year:

Once back in the Live Access Server click on, Time Series, which will change Select output to Line Plot
Enter latitude and longitude of your interesting location
Enter time range for January to December of one particular year

2. Make text files of the data by changing Select output to ASCII file (text). Save the files to your Desktop. Import chlorophyll-a data into Excel. Also import sea surface temperature and monthly surface all-sky data into Excel. Make Excel line graphs of the data. Saving your files to an ASCII file can be done as follows,:
Click on the ‘Save As’ tab at the top of the screen, from the ‘Select Format’ drop down menu choose ‘ASCII’, verify your date range and click ‘OK’. You will then be able to save the data by going to file, and Save Page As in your browser. This file can then be imported into excel as a text file.

3. Using your line plots, answer Question 4 below by writing a paragraph summary of your conclusions.


1. What information can you gather from these satellite data plots?

2. When is there the least chlorophyll in the water? What is your evidence?

3. When is there the most chlorophyll in the water? What is your evidence?

4. How are sea surface temperatures and sunlight related to the growth of plankton?


1. What other parameters in the LAS do you think may be correlated to the bloom times? Explore more parameters and seek correlations using the same procedure.

2. What are the unique characteristics of the Gulf of Maine are (i.e. what other regions have similar sea surface temperature and solar radiation patterns and do not have similar patterns of chlorophyll concentration? Why?)

2. Read information about the movement of phytoplankton by ocean currents from the Coastal Ocean Observatory Laboratory (Lesson Link). How can the movement of plankton be monitored?

Lesson plan contributed by Margaret Morton, South Bristol, Maine

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