Studying the Ocean From Space: Ocean Color

Plankton are tiny organisms that are carried by ocean currents. Plankton include phytoplankton, tiny single-celled plants which use chlorophyll to capture the energy in sunlight. The main types of phytoplankton are diatoms, dinoflagellates, and algae. Phytoplankton form the base of ocean food chains and also occur in freshwater habitats. The following activities will help you learn about these tiny creatures. (Choose one or more depending on your time and resources.) Helpful background information.

Exploration

PART 1: Draw an Ocean Food Web:

Use the given clues and information from reference books or encyclopedias to create a food web by drawing lines from each organism to what it eats. (You may want to add other creatures based on your research. Student Answer Sheet)
 

Clues:
 

1. Leatherback turtles sometimes mistake plastic debris for food.	4. "Zoo-" means "animal-".
2. Tuna are predators.	5. "Phyto-" means "plant-".
3. Krill are small shrimp-like zooplankton.	6. Check out the following Web sites:

 

1) Sea World Animal Resources	4) WhaleTimes: Fishin' for Facts Library
2) Fun Fish Facts!	5) Whale Watching
3) Krill	6) The Grass of the Sea

Exploration

PART 2: How Satellites Measure Phytoplankton Abundance:

Special instruments carried on certain satellites can detect and measure ocean color. Areas with little phytoplankton growth appear deep blue. Where phytoplankton are present, the color changes due to the pigments in the phytoplankton, primarily chlorophyll. The instruments record data which is first used to create a "greyscale map" composed of squares. Each square represents a specific location and is assigned a number corresponding to one of 256 possible shades of grey. The higher the value the darker the color and the more pigment is in that area of the ocean. Close up, a map of the part of the Pacific Ocean around Hawaii might look like the black and white image linked above.

In order to make sense of the data, each shade of grey is related to a specific chlorophyll concentration and a color is assigned to each range of values. For the maps you will be working with, the Greyscale to Color Conversion chart assigned is shown at right. Make several predictions based on where you think phytoplankton might be found.
 

BLANK MAP

Exploration

PART 3: Field Trip to Measure Phytoplankton Abundance (Optional Instructions Here)

Concept Introduction

PART 1: Using NIH Image to Study Ocean Color (download pc or mac as needed)

1A. Introduction to Nimbus-7 Ocean Color Data

1. Save, Introduction Stack,and Open NIH Image .

2. Select the Open command under the File menu.

3. To open the file entitled Introduction Stack , select that file in the dialog box by clicking on it and then click on Open .
 

4. After the stack of images opens, take as long as you wish to examine the image, then press the key with the period symbol (.) to move to the next image.
 

5. Take as long as you wish to examine the image, then press the period key to advance to the next image. Press the comma key (,) to go back to an image again.

6. When you are finished examining the stack, close the Introduction Stack file. To close the file, select the Close command under the File menu or click in the small box at the top left of the image.

1. Save and then use the Open command under the File menu to open the file entitled Annual Cycle Stack.
 

2. After the stack opens, select the Animate command under the Stacks menu while holding down the key numbered 1 to slow down the animation speed.)
 
 

The advantage of animating the stack instead of using the manual control is that the animation cycles repeatedly through the months of the year so that you can observe how the conditions in December lead into the conditions in January. With the manual control, January is the first image and December is the last and you cannot easily compare them.
 

3. After simply observing the annual cycle for a while, concentrate on each of the following questions one at a time:

Where are phytoplankton more abundant, in coastal areas or in the open ocean?
 
 

Where are phytoplankton more abundant, near the equator (at the bottom of the image), or away from the equator?

4. Press the right arrow key (->) or left arrow key (<-) to obtain manual control and then "back up" to the January image.

5. Use the arrow keys to move from image to image. Examine each monthly image more carefully to gather more information on the following question:

How does phytoplankton abundance change over the year?
 

6. Click the mouse to stop the animation.

7. Use the period and comma keys to move from image to image to answer the following question:

How abundant are phytoplankton near the mouth of rivers as compared to other sites?
 
 

To "zoom in" on the mouths of rivers, click once on the Magnifying Glass tool on the Tools menu to turn the pointer into a Magnifying glass, then move the Magnifying Glass over the image until you find an area near the mouth of a river. Click on the spot to enlarge the image. To zoom back out, go back to the Tools menu and double-click on the Magnifying Glass icon.

8. Compare the images for February and August to the predictions you created. How are the actual data different from your predictions?
 

9. Close the Annual Cycle Stack.

10. Close NIH Image by selecting Quit under the File menu.

Part 2: Explaining the Growth Patterns

Materials:

jars, wide-range pH indicator, graph paper,
liquid "plant food," straws, thermometers,
milk cartons, pitchers, or beakers

Overview:

Phytoplankton, like land plants, need plant nutrients to grow. Land plants get these nutrients from the soil. Phytoplankton absorb them from the water. Phytoplankton and land plants both use CO2 in photosynthesis, but for phytoplankton the CO2 must be dissolved in the water.

Nutrients from the land are continually washed into the ocean as rain runs off the land into streams and rivers. Human activities have about doubled the amount of plant nutrients entering the ocean.

The following activities will help you explain the patterns you observed in the images:

Explore the Effect of Fertilizer on Phytoplankton:

Place equal volumes from your phytoplankton samples into each of several jars. Add different amounts of liquid "plant food" to each. Place all jars on a sunny windowsill and observe any changes over time. Relate these observation to the ocean pigment data.

Explore How CO2 Dissolves in Water:

Pour some distilled water into a small jar and add a few drops of wide-range pH indicator solution (available from a scientific supply house or use red cabbage juice). Gently blow through a straw into the solution and notice the color change as CO2 in your exhaled breath dissolves in the water. Add distilled water and indicator to a second jar, filling it halfway. Tightly cap the jar and shake it to mix air into the water. Note the color change. Predict how wave action affects the amount of CO2 in ocean water.

Explore How Temperature Affects Dissolving of CO2 in Water:

Repeat the previous experiment, but this time heat the water first. Based on your observations, predict whether phytoplankton will grow better in warm water or in cool water.

Explore How Air Temperature Affects Water Temperature:

Fill several milk cartons, pitchers, or beakers to different depths with hot water and monitor the change in temperature over time. Based on your observations, predict how air temperature changes over the year affect water temperatures close to the equator and away from the equator, in deep areas and in shallow areas.

Examine how day length changes with latitude and month:

Use the information in the following table to make several line graphs comparing different latitudes in terms of the hours of daylight at various times of the year.

Hours of Daylight at Various Latitudes on the First Day of Each Month:
 

How would graphs for southern latitudes compare to these?
 
 

Use the graphs to help you interpret the phytoplankton growth patterns observed.

Part 3: Algal Blooms and Red Tides - Too Much of a Good Thing?

Materials:

Chesapeake folder of electronic images
copies of Chesapeake Bay outline maps
map of United States or North America

Overview:

A population explosion of phytoplankton is called an "algal bloom". (Since these single-celled plants reproduce by simple cell division this is very different from what we mean when we say that flowers are blooming!) In many coastal areas, too-high levels of phytoplankton (from natural or man-created conditions) are creating problems. How can an algal population explosion cause problems?

FAST FACTS:

1). Both phytoplankton and marine animals need oxygen. During daylight, phytoplankton produce more oxygen than they use, but at night both phytoplankton and animals compete for the available oxygen. If there are too many phytoplankton, some fish and other animals may die.

2). If the algal bloom occurs quickly, as is often the case, most of the phytoplankton will not be eaten by animals, because there is so much present. When these phytoplankton die, their decay will use up precious oxygen needed by animals. Again, some fish and other animals may die.

3). A different problem occurs when certain phytoplankton called dinoflagellates bloom. For unknown reasons, these phytoplankton produce a toxin which is harmful to many animals. The toxin can build up in the tissue of oysters, clams, mussels, fish, and squid, leading to the death of animals such as whales and dolphins that eat the contaminated tissue. Many fish may die directly from the toxins in the water, others may die from consuming contaminated prey. (Even humans can become affected and are discouraged from eating possibly-contaminated oysters and clams.) These phytoplankton often contain a reddish pigment and may become so numerous that a noticeable color can be seen where they are present. As they are carried by currents, a "red tide" results.

The Chesapeake Bay receives runoff from a 64,000-square mile area through several rivers. The program to monitor chlorophyll levels will help scientists determine whether efforts to reduce the flow of excess plant nutrients into the bay are effective. It is hoped that the annual average chlorophyll level, currently about 10 mg/m3, will return to the 1950s level of 1-2 mg/m3.
 

Observe Data on Algal Blooms in the Chesapeake Bay:

1. Locate the Chesapeake Bay on a map of the United States or North America. Notice the rivers that drain into the bay and the cities located on or near the bay.
 

2. Create a folder called Chesapeake Images and Save Chesapeake Images 01 through 28 to your hard drive. Open NIH Image .
 

3. Open Images 01 and 02 in your folder entitled Chesapeake ,
as follows: Select Open under the File menu. Double-click on the folder icon in the dialog box. Select 01 Chesapeake and then click Open . Again, select Open under the File menu. Select 02 Chesapeake in the dialog box and click on Open .

4. Select Tile Images under the Windows menu.

5. First notice that a different color scale is being used, with much higher concentrations than were indicated in the ocean images.

What color was used in the ocean data for concentrations higher than 10 mg/m3?

How many colors represent concentrations higher than 10 mg/m3 in the Chesapeake data?

How many colors were used to represent concentrations less than 2 mg/m3 in the ocean data?

What color is used in the Chesapeake data for concentrations lower than 2 mg/m3?

6. Another difference between the bay data and the ocean data is that the bay data shows the levels for specific days, while data for an entire month were averaged to create each of the ocean images. By looking at levels on particular days, it is possible to identify "blooms" - rather sudden (and often brief) increases in chlorophyll concentrations due to a population explosion of phytoplankton.

How many days apart were the data for these two images collected?
 
 
 
 

How much did the chlorophyll concentration change during this time at the following locations?

8. Select Open under the File menu. The contents of the Chesapeake file should appear in the dialog box. Click on Open All and then click on Open . Wait for all 28 images to open.

9. To create a stack, select Windows to Stack in the Stacksmenu.

10. Use the period and comma keys to move through the stack as before.
 

11. What do you notice about the chlorophyll levels during the time period from February 15 to September 28, 1994?
 
 
 
 
 

12. How do chlorophyll concentrations at the mouth of the bay generally compare to those at other sites in the bay?
 
 
 
 

13. Assuming that an algal bloom is indicated by chlorophyll concentrations of 25 mg/m3 or higher (yellow, gold, pink, or red),
on what 5 dates did the most-widespread blooms occur?
 
 
 
 
 
 
 
 
 
 

14. On blank outline maps of the Chesapeake, use a red pencil or crayon to color areas that are marked pink or red (chlorophyll concentrations 40 mg/m3) for each of these dates, labelling each
map with the date.

15. Close the stack.

16. Quit NIH Image .

17. Compare and contrast the 5 algal blooms in terms of their date, locations, intensity, and extent. (Print these if you need to)

Part 1: What Can We Do to Protect Our Coastal Areas?

Materials:

local maps, local telephone directory,
empty laundry detergent containers, regional maps

Overview:

Human activities have dramatically increased the transport of plant nutrients into coastal areas. Effort to reduce nutrient levels will be successful only if everyone becomes involved. The following activities may give you ideas on ways to help:

Find Out Where Your Wastewater Ends Up:

If your home is on a sewer system, wastewater first goes to the sewage treatment plant, where solids are removed and the sewage is treated, and then is discharged, usually into a stream, river, or lake. Contact your local sewage ("wastewater") treatment plant to find out where your wastewater ends up.

Check out the Ingredients in your Household Detergents:

Because phosphates in wastewater can stimulate algal growth, some communities have become concerned about the use of household detergents that contain phosphates. Check the ingredients in several detergents sold locally to determine if phosphates are present.

Find Out Where Your Local Runoff End Up:

All the precipitation which falls on land either evaporates, soaks in, or runs off to streams, lakes, or to the sea. Water in streams and rivers may eventually reach the sea, if it is not diverted and does not evaporate. Trace the water in nearby rivers all the way to the nearest coastal area.

Adopt A Stream:

Healthy streams are critical to maintaining healthy rivers and coastal areas. Find out about stream monitoring programs in your local area.

Find Our How Healthy Local Lakes Are:

Contact local agencies and inquire about the health of local lakes. Are the phytoplankton levels unnaturally high? If so, what steps, if any, are being taken to remedy the situation?
 
 
 
 
 
 
 
 

Part 2: Visiting Sites on the World Wide Web

The following sites have information you may find interesting or useful:

"Ocean Color From Space"
This site has lots of background information as well as many interesting images.

"Ocean Color"
This site suggests other phytoplankton-abundance comparisons using global data.

"SeaWIFS Project - Ocean Color Gallery"
As the title indicates, this is a gallery of images, made using ocean color data collected by the Nimbus-7 Coastal Zone Color Scanner, which operated from 1978 to 1986.

"Give Water a Hand"
This site provides a lot of suggestions of ways to prevent/reduce water pollution.

"JASON Project Aquatic Field Investigation"
This page describes how your school can participate in an international project by collecting data at a local aquatic site.

"Chesapeake Bay Program Home Page"
This site describes the efforts to restore the Bay.

"About Red Tide"
A good article on red tides in Florida.

"Additional Hydrosphere Resources"
This site has more links than you could ever hope to see.

A. Obtaining Additional Ocean Color Data:

A free set of 5 CD-ROMs containing Sea Surface Temperature data and Pigment Concentration data for 1978-1986 is available. To order it online on the World Wide Web, go to the Web address http://podaac-www.jpl.nasa.gov/mail-orders.shtml and select product #15, "AVHRR monthly global MCSST coregistered with CZCS data". Complete the order form as specified. You should receive your CDs in about a week.
 

The CDs incorporate data on daytime and nighttime sea surface temperatures and on daily ocean color. All images except the "climatologies" are monthly averages. (Climatologies for each month average the data over all years.) Both full-resolution and reduced resolution ("browse") images are included. Regional as well as global data sets are provided. In addition images showing actual data only ("valid images") are provided in addition to images in which missing data has been filled in by interpolation ("interpolated images").

Converting Files from HDF Format to PICT Format:

To view the images with NIH Image , you must first open them with NSCA Image , provided on the CDs in the "MAC" folder in the "SOFTWARE" folder. Open NCSA Image , then pull down the File menu and click Open . Select an image file to open and click the button marked "HDF", then click Open . After the image is displayed, select Save As and choose "PICT", then save the image to a folder on your hard drive. The saved PICT image can later be opened and manipulated using NIH Image .

The full resolution files are quite large. Unless you have ample RAM available, work with the global "browse" images, in which each pixel represents 1 degree latitude and 1 degree longitude, or the regional images.

Suggestions for Student Activities:

1. Examine Ocean Color Data for Various Regions:

The Northeast Atlantic region includes data for the Mediterranean Sea. Compare the phytoplankton abundance in the Mediterranean Sea to that in the rest of the region. Are the results surprising?

1. Compare Sea Surface Temperature Data and Ocean Color Data:

B. Obtaining Additional Data for the Chesapeake Bay:

Additional color data for Chesapeake Bay is available at the NOAA Chesapeake Bay Office: Ocean Data Acqusition System web site at http://155.206.19.100/ODAS.html . The data can be downloaded using Netscape as GIF files.

Converting GIF files to PICT files using GIFConverter:

GIFConverter is a shareware program you can download off the Internet. Launch GIFConverter and open the image. Select Save As from the File menu and then select "PICT". Click on Save. The saved files can later be opend and manipulated with NIH Image .
 

Suggestions for Student Activities:

1. Examine the Data for 1995:

1. Examine the Data for Other Years: