Channel Islands Teacher’s Guide

The amount of fluorescent light that phytoplankton emit is a relatively small value. Fluorescent light is radiant energy, and its unit is provided in watts per square meter per micrometer per steradian. When you use the Probe or Scatter tools, you will notice that the whole fluorescence unit is divided by 1,000. This means that you should shift the decimal point three spaces to the left for whatever numerical value you observe for fluorescence; i.e., a numerical readout of 21.4 actually equals 0.0214 watts per square meter per micron per steradian. Also, in this lesson, sea surface temperature values are provided in degrees Celsius. The unit value for chlorophyll concentration is milligrams per cubic centimeter.

Answers to questions:

Do you observe any relationship between areas of warmer and colder sea surface temperature and areas where there is higher and lower chlorophyll concentration? If so, why do you think there is a relationship? If not, why not?

  • Yes, there is a negative correlation between sea surface temperature and chlorophyll concentrations. Generally, areas where the surface is colder are where deeper, more nutrient-rich waters are allowed to upwell to the surface. These nutrients provide nourishment to phytoplankton. When there are abundant nutrients, phytoplankton populations can bloom exponentially in a matter of days. Thus, you generally see higher chlorophyll concentrations in pockets of colder water.
  • Click on Outline Region and trace an area where you observe high chlorophyll content. Click the Chlorophyll and Sea Surface Temperature thumbnails to select those for comparison. Then, click Scatter. Another window will appear with a graph containing data points comparing the two data products. The more correlated the two images are, the more the grouping of data points will converge along a 45-degree angle line between the X- and Y-axes.

Do you see a relationship between areas of high chlorophyll concentration and where there are high fluorescence values?

  • Yes, there is a strong positive correlation between areas of higher chlorophyll concentration and higher fluorescence values. Phytoplankton have relatively short life spans—generally a day or so. As generations of the plants begin to die off, they become stressed and their ability to photosynthesize tapers off. They begin to emit the sunlight they absorb as heat and fluorescent light. Scientists use the MODIS fluorescence product, together with the chlorophyll product, to estimate the productivity of a phytoplankton bloom—that is, how much carbon is being drawn down out of the atmosphere and fixed into the tiny plants’ bodies during photosynthesis.
  • Click on Outline Region and trace an area where you observe high chlorophyll content. Click the “Chlorophyll” and “Fluorescence” thumbnails to select those for comparison. Then, click Scatter. Another window will appear with a graph containing data points comparing the two data products. The more correlated the two images are, the more the grouping of data points will converge along a 45-degree angle line between the X- and Y-axes.
  • In another exercise, you might click Plot Transect and then draw a line across the scene. Another window will appear that plots on a graph the unit values along the transect line for all three of the data products. Again, encourage your students to look for the negative correlation between sea surface temperature and chlorophyll as well as the positive correlation between chlorophyll and fluorescence. Try clicking and holding the mouse button as you move the transect line around. Notice how the unit values move in real time. This gives students an interesting way to analyze the data.

Additional Slides as Needed (Microsoft PowerPoint files)

  • Introduction to Remote Sensing (5.83 MB)
    This presentation is an overview of remote sensing, what it is, why we use it, and how it works. Slides include the definitions of common remote-sensing terms, and examples of images captured by different remote sensing instruments. The presentation also highlights key steps in the history of remote sensing and ends with a spectacular global image of the Earth’s surface combined with ocean temperatures, both of which were captured by the MODIS sensor on the Terra satellite.

  • Leaf Reflectance (3.02 MB)
    This presentation addresses how and why vegetation interacts with sunlight the way it does, and how that interaction determines what a satellites “sees” when it looks at vegetation. The presentation includes examples of how vegetation looks different in different parts of the electromagnetic spectrum, and how using “invisible” parts of the spectrum can distinguish vegetated from non-vegetated surfaces as well as one type of vegetation from another. The presentation also includes brief discussion of photosynthesis, including schematic drawings of the process and structures involved, as well as graphs showing the range of sunlight that best drives the process.

  • The Human Eye (1.33 MB)
    This presentation briefly summarizes the main characteristics of the human eye and vision, and makes comparisons to the vision of other creatures. It includes electron micrograph images of the structures of the eye, as well as graphs that illustrate the link between our vision and the energy output of the Sun.