Weeks 4,5: Algae, Ocean temperatures

Weeks 4 and 5: Algae and Ocean Temperatures


1.) Read ch 3 of The Seaside Naturalist to familiarize yourself with the different types of seaweeds.

Important note: As you read through this chapter of The Seaside Naturalist, you will notice that the author consistently calls seaweeds and other algae “plants.” This is a common error.

In fact, algae are not plants , but exactly what they are is a bit of a mystery. Green algae are the most plant-like of the bunch and are often lumped in a subcategory along with the true plants. But  scientists place most other algae in entirely different kingdom called protista. You may be familiar with protists only as the single celled critters amoeba, euglena, and paramecium, but there are many, many more! In fact, these tiny organisms (which can be either plant-like, animal-like, or fungus-like) make up a large percentage of the plankton we looked at earlier (in other words, phytoplankton are plant-like, but not plants).

But not all protists are small. Many protists are colonial or multicellular, including all seaweeds, some of which grow quite large like the giant kelp which can reach 120 feet in length!

The only true plants in this chapter are the sea grasses and mangroves described at the end (which we will cover separately in the next section). So, just keep this in mind as you read and ignore all the “plant” references until then.

Another issue: blue-green algae are not algae, but actually cyanobacteria.

I know it’s confusing. Even scientists are confused by all of this. Work is still being done to figure out the relationships amongst these organisms, and it seems likely that kingdom protista will eventually be divided into several distinct kingdoms. But until then, you are safe just considering seaweed as algae, and algae as protists, which are distinct from plants. Now lets move on, shall we?

2) Spend the next few days visiting as many different sites as you can and collecting a variety of seaweeds. The more varied the sites the more diverse set of seaweeds you will collect. Some suggestions are sandy shores, rocky shores, sea walls, tidal flats, open water,boat hulls, and pilings.  Look for the slippery blue-green algae (cyanobacteria) on boat ramps and dock pilings. Look in sea grass beds and mangroves, but do not collect the grasses or mangroves themselves( remember those are plants).

3) Sketch your seaweeds into your notebook and identify them to the best of your abilities, grouping them into red, green, brown, etc. You may want to use a better guide than the simple sketches in your book. A local guide to seaweeds would be best.

4.) Look at some of your seaweed under a microscope. Notice the cell structure and the often beautiful patterns they make. Look for the green, red, or brown pigmented chloroplasts that function just like the chloroplasts of plants to capture sunlight for photosynthesis. They are much easier to see in algae! Draw what you see in your notebook (at least one sample).

5.) Seaweeds are yummy! Look up some recipes and check out your local markets for edible  seaweed!Make sushi, seaweed salad, or other delectable dishes from seaweed. You could even have a taste-test party! Be sure to record your efforts in your notebook.

6.) Algae can be dangerous! Read all about harmful algae blooms (HABs). What types of harmful algae blooms are most prevalent in your area (check out this map)? What can you do to protect yourself?  Finish up by watching this series of short video clips about  scientists  studying harmful algae: The Hunt for Killer Algae.

*Just for fun* do one of the algae crossword puzzles here.

Ocean Temperatures: (alternative assignment for younger kids at bottom of this page)

7.) Read the following article:Marine Bio-Ocean Temperatures. Make sure you understand the following relationships and briefly summarize them in your notebook:

  • temperature and depth (thermocline)
  • temperature and density
  • density and currents (great ocean conveyor belt)
  • change of seasons and algae growth

8.) copy the thermocline graph into your notebook and write a brief summary underneath it.

9.)Print up a small copy of a world map and draw in “the great ocean conveyor belt”.  Attach into your notebook. Write a brief summary underneath your map.

10.) Go to the website Ocean Motion . This is a site where NASA makes available satellite imagery data for ocean temperatures and chlorophyll concentrations (used to indicate algae growth). Do the following tasks, answering any  questions in your notebook:

  • Set the year to 2008, any month, and the parameter to temperature.
  • Click on a spot somewhere in the north Atlantic. A new window should pop up which shows a graph of ocean surface temperatures for the years 1981-2008. (You may need to drag and  expand this window to look at all of it).
  • What are the typical high and low yearly temperatures for this area?
  • In what approximate month  are the temps the highest? In what month  are they the lowest?
  • Repeat this observations for several spots in the northern hemisphere, in both the Atlantic and Pacific oceans. Do you notice any trends? Choose one graph and copy a representative section (about 5 years or so) into your notebook.
  • Now choose some spots in the southern hemisphere and repeat the observations. What differences do you notice?
  • Change the parameter from temperature to chlorophyll.
  • Click on a spot in the north Atlantic and a graph of chlorophyll concentrations for the years 1998-2006 should pop up. Study the graph. On average, at what times of the year are mean chlorophyll concentrations the highest? At which are they the lowest?Repeat this for several spots in the northern hemisphere. Any trends?
  • choose one spot and copy a representative section into your notebook.
  • Now choose some spots in the southern hemisphere, study the graphs, and note trends.
  • Based on your reading from the Marine Bio site, how can you explain  this data? Write an explanatory paragraph in your notebook.

Alternative temperature assignment for younger students (or older students just for fun):

Go to Steve Spangler Science and do the following experiment:Colorful convection currents. Make sure to write up your materials, methods,results and discussion in your notebook. Be sure to include photos or diagrams and label them.


  1. Here is our entry for Algae day, will do a separate ocean temps post later this week, eek I think we’re a little behind! Hugs, Mere


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