The Oceans: Carbon Sink or Source?

Part B: Phytoplankton: Nature's Green Machines

In Part A, you learned that the ability of the oceans to absorb and sequester a lot of carbon is dependent on phytoplankton—tiny one-celled photosynthetic organisms that float in the upper surface of ocean. Given phytoplankton's importance in the ocean carbon cycle, let's learn more about phytoplankton, where they flourish best and under what conditions.

Begin by watching a NASA video The Ocean's Green Machines. In addition to watching the video, read an accompanying NASA article entitled What Are Phytoplankton?

As you watch the video and read the article, take notes on the topics listed below. Your teacher may want to assign specific topics to individuals, which can then be shared within your group in a jigsaw activity.

Topics:

the role of phytoplankton in the carbon cycle
what phytoplankton need to grow
why scientists think it is important to study phytoplankton
how do satellites measure phytoplankton blooms
global locations where phytoplankton flourish and grow
why phytoplankton flourish in some locations but not others
the relationship between warmer oceans and phytoplankton productivity
differences in phytoplankton growth from season to season and year to year

Next, watch a NASA visualization of a 10-year data set of phytoplankton growth. The satellite is measuring the amount of chlorophyll used by phytoplankton to photosynthesize. Pay careful attention to the phytoplankton blooms—where they happen and any seasonal variability that you observe. Phytoplankton blooms are considered to be the "greening up" of the oceans. Hint: Paying attention to what the terrestrial vegetation is doing will give you a clue as to the seasonal variability. Reading the information on the website will help you interpret the visualization.

Show me how to view this NASA visualization successfully

Hide

When you bring up the web page, click on an available format from the right hand menu that would be appropriate for your computer. The best format is the first one on the list: 1280x720 (30fps) MPEG-4 254 MB. However, if your computer has streaming problems, 512x288 MPEG-1 51 MB would be best.
The colors are very important to observe;
Dark blue = very low phytoplankton numbers. No bloom.
Green to red = high phytoplankton numbers generating large blooms.

Now, use your notes from the movie, the article, and the visualization to help you answer the Checking In and Stop and Think questions, below.

Checking In

If their needs are met, phytoplankton populations can grow explosively, causing large phytoplankton blooms. Which of the following factors can cause phytoplankton populations to "bloom"? Check all that apply.
Sunlight and CO2

Nutrients containing essential elements such as nitrogen, iron and phosphorus

Warm tropical water

Areas of cold upwelling along coastlines
When you observed the NASA visualizations, where were the largest phytoplankton blooms located? Check all that apply.
In the middle of large oceans such as the Pacific Ocean

Along coastlines where upwelling occurs

Cold Arctic and Antarctic oceans

Coastlines where nutrients are washed down from rivers

Stop and Think

1. A warmer climate produces warmer oceans. Phytoplankton reproduction requires important nutrients such as nitrates and phosphates. When oceans warm, the ability of deep ocean currents to bring these important nutrients up to the surface is reduced.

a. What effect(s), if any, would this have on phytoplankton reproduction, the biological pump, and the ocean as a large carbon sink?
b. What effects, if any, would this have on other parts of the carbon cycle?

Optional Extensions

Have you ever wondered how NASA visualizations like the one on the right are created? If you have the time, watch this SciFri video Creating Earth
Read the other articles on Phytoplankton and ocean research in the NASA Earth Observatory features collection. You can access these articles at here
Grow your own phytoplankton and use it to design an experiment on variables that affect phytoplankton growth. Here is one of several videos that tells you How to grow phytoplankton.
Carry out a case study on predicting the Spring Phytoplankton Bloom in the Gulf of Maine. When is Dinner Served? Predicting the Spring Phytoplankton Bloom in the Gulf of Maine

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