Bioluminescence: Living Light

Below 3,300 feet (1,000 meters), the waters of the ocean are dark and cold . No sunlight penetrates these depths, and 90 percent of the creatures here produce their own light in a chemical process called "bioluminescence." In this lesson students will learn about bioluminescent creatures and the underwater world in which they live.

Geography, science, biology

Standard 3: "How to analyze the spatial organization of people, places, and environments on Earth's surface"
Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"

One to two hours

• Computer with Internet access
• Several shoe boxes with lids
• Black construction paper
• Black paint and paintbrushes
• Scissors
• Tape
• National Geographic Atlas of the Ocean (optional)

Students will

• describe how organisms use bioluminescence;
• perform an experiment to learn how animals use bioluminescence for camouflage; and
• describe the habitat and characteristics of at least one bioluminescent organism.

Read students the following summary:

Bioluminescence—the word we use to describe the phenomenon that occurs when animals emit their own light—occurs in certain animals as a result of chemical reactions inside them. Organisms use their built-in lights in a variety of ways. Some species light up to confuse or blind attackers or to illuminate them so larger predators can attack. Some creatures, such as the dragonfish and the anglerfish, use luminous lures to draw the prey in close enough to eat it. Light-producing organs on the sides of other species, such as the hatchetfish and the lanternfish, make them invisible to predators viewing them against the lighted waters above them. Still other deep-sea species use distinctive light patterns to identify one another in the darkness or to find potential mates.

The ocean makes up 95 percent of the part of the world in which life exists. Because so many of the ocean's creatures use the "living light" of bioluminescence, it may be the most common form of communication on Earth.

Divide the class into small groups. To see how bioluminescence can provide camouflage, ask each group to paint the inside of a shoe box black. Then have them poke holes in one end of the box and cut a viewing hole in the other.

Next, ask them to cut two fish shapes from black construction paper; poke numerous holes in one and leave the other complete. Ask each group to hang the complete fish shape from the shoe box lid, then return the lid to the box. [Note: If you like, use the Web sites in the "Suggested Student Assessment" section to show students the shapes of fish that live in the deep sea, such as hatchetfish or lanternfish. Some of them look quite different from the fish students are probably imagining!]

Have them hold the box to a light and look through the viewing hole. Do they see a silhouette of a fish? Ask them to repeat the exercise with the fish with holes.

Ask the groups to comment on the difference in appearances of the two fish. Make the point that the complete fish shape is silhouetted when seen against scattered light, while the fish with holes blends into the background and is difficult to spot.

Discuss with students other problems that might confront creatures of the deep. Are there fewer sources of food available? Is the water that deep colder than the water closer to the surface? You might want to explore the following Web sites as a class to answer these questions:

PBS: NOVA Online—Into the Abyss
Life Without Light: Discoveries From the Abyss
Woods Hole Oceanographic Institution: Dive and Discover—Expeditions to the Seafloor

Ask each student to research one of the fish mentioned in the opening section of this lesson—lanternfish, hatchetfish, dragonfish, or anglerfish—and write a one-page paper about it. The paper should contain a physical description of the creature (you may want to suggest students include illustrations) as well as information about its habitat and how it obtains food. The above Web sites, as well as the ones listed below, will help them with their research:

Monterey Bay Aquarium: Fishes (see species list on left)
Sea and Sky: Monsters of the Deep (see species list at the bottom of the page or click on flashing lights)
UC Santa Barbara: Bioluminescence Web Page—Photos

When the students are finished with the assignment, read to the class at least one paper about each of the four types of fish. They are all bioluminescent, it is true, but what else do they have in common? The most obvious characteristic is that they are fairly small creatures, and that they have adapted to the scarcity of food and cold temperatures at such great depths.

Refer students to pages 184-185 in National Geographic's Atlas of the Ocean where they learn that visible light sensors and heat-sensitive infrared sensors on satellites help monitor the ocean. [Note: As an alternative, you can get similar information from Monitoring the Earth from Space with SeaWiFs .]

Ocean color as viewed from a satellite is a function of the amount of chlorophyll in the water—the green pigment in plants necessary for photosynthesis. Chlorophyll is visible as it responds to light. Deep where bioluminescent creatures reside, little to no light exists; but many spend the day in the deep, then move to upper layers at night to graze on plants. Have students surmise how much impact this migration may have on the colors in the satellite (SeaWIFS) images opening most chapters in the Atlas or in these examples from the SeaWiFs site .

This lesson is made possible by a generous grant from the National Oceanic and Atmospheric Administration National Marine Sanctuary Program.

Harbor Branch Oceanographic Institution: Bioluminescence
Monitoring the Earth from Space with SeaWiFs
PBS: Secrets of the Ocean RealmCreatures of Darkness
Sea and Sky: Monsters of the Deep
UC Santa Barbara: Bioluminescence Web Page