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glossary

Plankton refer to marine organisms that cannot swim against the current. They are generally free-floating, and many have physical structures that help them either move up and down the water column or remain buoyant (i.e. suspended) near the surface. Plankton can be microscopic, like diatoms and radiolarians, or stretch up to 130 ft in length, like some colonial siphonophores. In this investigation, it is the microscopic plankton that is of importance.

Microscopic plankton are the base of the food webs in the marine environment. Therefore, their presence and availability influences the abundance of countless other marine organisms.

Plankton that can carry out photosynthesis to produce their own food are known as phytoplankton. These are the "plants" in the ocean. They produce most of the oxygen in the air that we breathe, and form the base of almost all food chains in the ocean. Their abundance is influenced by the availability of nitrogen and phosphorous.

 Almost all organisms in the ocean start out their life as a microscopic zooplankton. These are the egg and larval stages of their lives. Some zooplankton eventually grow into a large adult stage, like anchovies, blue crabs, corals, sea urchins, etc. Other animals remain small their entire life, such as copepods and krill.

(www.chesapeakebay.net/info/plankton.cfm)

(www.cnas.smsu.edu/zooplankton/epischura.htm)
HOW IS PLANKTON IMPORTANT?

Phytoplankton make nitrogen into a chemical form that is usable by marine animals. N & P are locked in organic material (as the amino acids, protein, and DNA) even after death. Dead organic material sink to the ocean bottom, and are consumed by other organisms on the way down or decomposed by bacteria.

N is put back into the marine environment via animal waste and byproduct from bacterial decomposition. Phytoplankton take up this nitrogen in the water during photosynthesis, and animals acquire the necessary nitrogen when they consume the phytoplankton. However, phytoplankton are not found at the ocean bottom. Phytoplankton rely on upwelling mechanisms to vertically transport N & P back up to the surface.

(www.soc.soton.ac.uk/CHD/education/posters/productivity.html)
NITROGEN AND PHOSPHOROUS

Aside from oxygen and carbon dioxide, all organisms need other essential nutrients to survive. Nitrogen (N) and phosphorous (P), in the form of nitrates and phosphates, are needed for producing amino acids and ATP. Amino acids are the building blocks of protein, which are essential for life. ATP is cellular energy, thus without ATP cellular activity would not take place.

Autotrophs, like phytoplankton, can take up nitrates and phosphates from the water. Heterotrophs, like zooplankton and fish, acquire N & P by consuming organic material, such as phytoplankton, other animals, or waste products. Heterotrophs need autotrophs to transform nitrogen and phosphorous into a chemical form that they can actually use.

The high availability of nitrogen and phosphorous along Peru's coast makes it a rich environment to support an abundance of anchovies.

  1. What happens to the anchovy population when there is a reduction in plankton supply?
  2. What can alter the plankton supply?
  3. When would you expect plankton to be most abundant?
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This web site was created by Lynn Tran at the North Carolina State University, Department of Mathematics, Science, and Technology Education on 7/12/03. Faculty advisor Dr. David Eggleston, NCSU, Department of Marine, Earth, & Atmospheric Sciences. Last updated December 29, 2003 .