NASA Educational Workshop

SeaWiFS: Biology




Phytoplankton: Vital Statistics

Diameter: < 1 um to over 100 um Penny

If you stack 1000 one micron phytoplankton end to end, the length of the stack would equal the width of a penny! (18,000 would fit across the face)

Coke can Concentration: 1000's to 1,000,000 per milliliter

If you fill a Coke can with seawater sampled from a thick, oceanic phytoplankton bloom, the can may contain a many as 75 to 100 million cells!

Global Biomass: < 1% of the plant biomass on earth


Tree BUT responsible for nearly half the net photosynthesis of the biosphere!



Pyrrophytes (dinoflagellates)


Diatoms (Bacillariophyceae): The Biogeochemical Workhorse


Satellite Chlorophyll and Photosynthesis

Satellite Chlorophyll and Photosynthesis



gas exchange

Carbon Cycling in the Oceans

Carbon Cycling


Q: Why are satellite chlorophyll measurements important for understanding photosynthesis in the oceans?

A: Because chlorophyll concentrations tell you the biomass of pigment in the water being used by phytoplankton for photosynthesis.

Q: What are the major losses of carbon in the marine food web?

A: (1) Release of CO2 back into the water/atmosphere
    (2) Release into the dissolved organic pool
    (3) Sinking of dead phytoplankton and zooplankton waste to the sediments

Q: In contrast to the above question, what are major carbon storage pools in terrestrial systems?

A: (1) Plant roots and stems
    (2) Storage of organic matter in soils

Q: How does phytoplankton photosynthesis influence atmospheric carbon dioxide concentrations?

A: Carbon dioxide is constantly exchanged between the atmosphere and ocean. Photosynthesis extracts carbon dioxide from the water to form plant biomass. The decrease in carbon dioxide in the water consequently requires that more atmospheric carbon dioxide is taken to re-establish the equilibrium.

Q: What are three examples of fossil carbon reservoirs of biological origin?

A: (1) Coal
    (2) Calcium carbonate (e.g., Hill of Dover)
    (3) Petrolium


  1. View phytoplankton under a microscope: Samples of phytoplankton can be acquired from a local pond using a plankton net or filtering water through a coffee filter. Fossil remains of diatoms may be available from the local swimming pool supplier -- ask for a pool filter that uses diatomaceous earth.

  2. Measure phytoplankton: What is the range observed? Can you calculate the concentration per volume of water? Can you calculate the cell volume based on your measurements and simple assumptions regarding the general shape of the cell (e.g., approximate the cell as a sphere, cylinder, or cube)?

  3. Identify phytoplantkon: Can you find dinoflagellates? Diatoms? Green algae? What types of diatoms do you see: centric or pennate? Single cells or chain forming? Do the diatoms have long spines? What might these be used for (e.g., influence sinking rate or defense against zooplankton)?

  4. Follow changes in species: If readily available, periodic sampling of a nearby pond over the course of spring might give a nice view of how the dominant phytoplankton in a pond changes with time. What might be the reasons for this (e.g., changes in the zooplankton population, nutrients, light, temperature, other)?

rainbow line

SeaWIFS biosphere globe

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Mike Behrenfeld(