SCIENCE

A new study is calling on the world’s sailors to help map the oceans’ phytoplankton, microscopic organisms that form the bedrock of marine food webs. (BBC)

Use our resources to learn how plankton makes the world go ’round.

Watch this video to learn how to use the free Secchi app—then use it!

Want more information on plankton? Of course you do! Watch this awesome video and visit Ocean Drifters to see what’s going on beneath the waves.

Discussion Ideas

• According to an expert quoted in the BBC article, “Away from estuaries and more than a kilometer from the coast, the main influence on water clarity is phytoplankton.” Besides the presence of phytoplankton, what factors may impact the turbidity (clarity) of estuaries and other bodies of water close to shore?
  • coastal erosion may introduce sandy sediment to the water
  • runoff from human activity can contribute to turbidity closer to land:
    • runoff from industry
    • runoff from agriculture
    • runoff from urbanization, such as storm drains and paved surfaces

• Watch our great video, “Plankton Revealed.” The video describes two major types of microscopic marine organisms—phytoplankton and zooplankton. What is the difference between the two? Why is the Secchi citizen science project only measuring phytoplankton?
  • Phytoplankton, like land plants, use photosynthesis to create oxygen and nutrients. Phytoplankton are producers in marine food webs.
  • Zooplankton are primary consumers in marine food webs—they consume phytoplankton.
  • The Secchi disk project is focusing on phytoplankton because it’s the basis of nothing less than life as we know it. “Ultimately, phytoplankton determines the amount of fish in the sea and the number of polar bears on the ice,” says the expert interviewed by the BBC. As goes phytoplankton, so goes the ocean.

• Work through the questions in “Plankton Revealed.” For example, why do marine biologists and citizen scientists find more phytoplankton at the top of the water column?
  • Phytoplankton relies on sunlight (as well as temperature and nutrients) for photosynthesis. Sunlight only permeates to upper layers of the ocean, called the epipelagic or euphotic zone. Below this zone, few phytoplankton have the necessary sunlight for photosynthesis.

• Besides Secchi disks, what are some other ways marine scientists measure plankton’s impact on the marine ecosystem? Watch the “Plankton Revealed” video for some examples.
  • scoop them up with a net
  • collect them in containers
  • collect core samples from the seafloor

• Do you live near the ocean? Do you know someone who does? What are you waiting for?
  • Make a Secchi disk. A Secchi disk is a 30-centimeter (1-foot), flat, white disk attached to a tape measure or a rope, and weighted from below. Use these instructions, but make sure your disk is 30 CENTIMETERS, not 20. This is an easy measurement to make, just one foot in diameter.
  • Download the (free) Secchi app and record your data. Any questions about the project? They’re answered here.
  • Compare your results with others in what promises to be the world’s largest global marine survey!