Phytoplankton produce half of the oxygen we breathe and are the base of the ocean food web! So they provide a great topic for lessons about the oceans.
In the, researchers determined that it was the amount of light and nutrients that determined when and where we observe large blooms of phytoplankton from North Carolina up to Massachusetts (see the What’s Hot in Ocean Sciences article in the Winter 2011 newsletter for a summary of the paper http://coseenow.net/mare/newsletter/winter2011/ or see below for a copy of the paper).
But what does that mean for your students? How can you incorporate some of this research into your classroom? Below I have developed a way to bring up these topics (Introducing these Topics) and then provided a list of multiple phytoplankton lesson plans that you can use with your students (Phytoplankton Lesson Plans).
Introducing these Topics
Take time to talk with your students about why it is important for phytoplankton to “stay” near the surface sunlight for photosynthesis. Help your students understand that the two things that phytoplankton, like all plants, need to survive are: energy from the sun and nutrients. Help the students understand that the need for sunlight and nutrients explains our observations of varying amounts of phytoplankton in different parts of the ocean and at different times of year.
First talk about the energy from the sun, ask the students if light from the sun penetrates everywhere equally in the ocean (no, only in the photic zone). Then ask the students if sunlight penetrates into the ocean to the same depth every day (no, if it is stormy). Ask the students if they think these two factors effect where and when phytoplankton bloom (yes). Then you can use a map of the Atlantic Ocean to show students one of the findings from the Xu et al. (2011) paper: that there are blooms in phytoplankton biomass off of the east coast in the spring (when it is sunnier than the winter).
Next talk with your students about nutrients. As organisms (e.g., phytoplankton, zooplankton, fishes) die in the ocean they often sink to the seafloor where they are decomposed into nutrients. This process results in a pool of nutrients near the seafloor. Use questions about what the students know about plankton sinking to help them realize that there would be a build up of nutrients at the bottom of the water column (the pool of nutrients). The nutrients do not float to the surface on their own, but rather are brought to the surface when the water column is mixed (meaning water at the surface mixes with water near the seafloor). Two main processes can drive this mixing: 1) the cooling of sea surface temperatures to temperatures more similar to the bottom waters (when there is a large difference in temperature this creates a thermocline in the water column and water of different temperatures “act” like two separate water bodies, aka no mixing) and 2) storms over the ocean churn up the water at the surface, which results in mixing of the water throughout the water column. The Xu et al. (2011) paper demonstrated that in the fall/winter seasons off the east coast both of these processes occur (cooling of sea surface temperatures and increased storm frequencies). Therefore, there is an increase in nutrients at the surface and thus an increase in the phytoplankton biomass at the surface.
• Map of Atlantic Ocean
• Global maps of sea surface temperature and chlorophyll from July 2002 to Oct 2011 from the NASA Earth Observatory (http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MYD28M&d2=MY1DMM_CHLORA)
• Maps of Pacific Ocean in May and November from the NASA Earth Observatory- Differences from Season to Season (http://earthobservatory.nasa.gov/Features/Phytoplankton/page4.php)
Phytoplankton Lesson Plans
1. THE GREAT PLANKTON RACE – phytoplankton diversity and sinking adaptations (Marine Activities Resources & Education (MARE), Lawrence Hall of Science, University of California at Berkeley, http://mare.lawrencehallofscience.org/curriculum/teacher-guides/gr5-open-ocean)
2. THE GULF STREAM VOYAGE/BIOLOGY – changes in phytoplankton concentrations over space and time from satellite images (Stevens Institute of Technology, Center for Improved Engineering and Science Education (CIESE) 2004, http://www.k12science.org/curriculum/gulfstream/teacherbiology.shtml)
3. WHAT COLOR IS THE OCEAN: AND WHY DO YOU NEED A SATELLITE TO TELL YOU? – concentrations of phytoplankton and satellite imagery of oceans from space (SeaWiFS, http://oceancolor.gsfc.nasa.gov/SeaWiFS/TEACHERS/sanctuary_3.html and other resources at the SeaWiFS Teacher Resources website: http://oceancolor.gsfc.nasa.gov/SeaWiFS/TEACHERS/)
4. OCEAN PRODUCTIVITY ACTIVITY – variation of phytoplankton in space (University of Rhode Island, http://kids.earth.nasa.gov/seawifs/phyto4.htm)
5. WHEN IS DINNER SERVED? PREDICTING THE SPRING PHYTOPLANKTON BLOOM IN THE GULF OF MAINE– using satellite data to make predictions about phytoplankton in space and time (Earth Exploration Toolbook, http://serc.carleton.edu/eet/phytoplankton/index.html)
6. MEADOWS IN THE SEA – phytoplankton photosynthesis, food webs, phytoplankton diversity (“Whales in the Classroom: Oceanography”, Lawrence Wade, Singing Rock Press, Minnetonka, MN, 2005)
7. UPWELLING: THE UNDERWATER ELEVATOR – geology and geography that results in upwelling/plankton blooms, annual variation in phytoplankton (“Whales in the Classroom: Oceanography”, Lawrence Wade, Singing Rock Press, Minnetonka, MN, 2005)