Algae Connections to Chemistry Classrooms

The theme to this year’s Chemists Celebrate Earth Week (April 16-22, 2023) is “The Curious Chemistry of Amazing Algae”.¹ I have to admit that when I think of algae I often think of green mushy material overrunning everything, much like in the picture in the summary, and the chemistry connections might not seem obvious at first. As the old joke goes: If it’s green and slimy it is biology, if it stinks it is chemistry, and if it doesn’t work at all it is physics. However, algae can be connected to chemistry topics in a number of different ways, some of which will be described in this post.

 

Algae Glows: Chlorophyll Fluorescence

Some dinoflagellate algae in the ocean produce light by bioluminescence using chemical reactions involving luciferin. This phenomenon is described in a recent edition of the American Chemical Society publication Celebrating Chemistry.² This is also explored as part of a traveling museum exhibit called Creatures of Light: Nature’s Bioluminescence, which I saw at a local museum last summer and thought was quite informative.^3,4 Bioluminescent algae is even referred to in the 2016 Disney movie “Moana”.⁵  If bioluminescent algae are not available to show to a classroom, other examples of bioluminescence in various parts of the world include fireflies. Some forms of algae can produce a glow via a completely different phenomenon: chlorophyll fluorescence.⁶ Chlorophyll from a variety of plant sources can produce a reddish fluorescence. Figure 1 shows a sample of local pond water containing some green colored algae. A violet light beam (405 nm wavelength) from a pocket laser is shined into the water. Where the beam strikes the filaments of algae, their chlorophyll glows with a pink color. NASA has used the Moderate Resolution Imaging Spectroradiometer (MODIS) on its Aqua satellite to monitor the reddish fluorescence from chlorophyll in plant life in the ocean.⁷ It has been found that plant life actually fluoresces more intensely when it is in a less-healthy, iron-poor environment. 

 

Figure 1. Excitation of chlorophyll with a 405 nm laser to produce pink fluorescence  

 

What Algae Takes

Algae are autotrophs, producing their own food, but they still need energy and matter resources. Where these resources are available, algae can thrive. Figure 2 shows greenish algae growths in a cave that obtain energy from light produced by the electric lighting.

 

Figure 2. Algae (circled) growing on cave formations near lights in Bridal Cave, MO.  

 

Another example of algae thriving when provided with resources are blooms of algae that can occur in a variety of waterways. Recent national news has been covering the large bloom of brown algae (Sargassum species) in the Atlantic Ocean.⁸ There is a likelihood that the bloom is thriving from nutrients washing from the land into the sea. Now at least some of that algae is coming back to land. The rotting seaweed contains arsenic, can produce hydrogen sulfide, and can decrease the oxygen level in nearby water to produce dead zones with few fish. Situations similar to this, with algae blooming and then dying and rotting to produce oxygen depleted waters, happen in many places around the world. Producing algae for a demonstration is quite simple, as it is very easily grown in a fish tank.

An excellent exhibit of natural waters and ecology and chemistry can be found at Splash! Into the Edwards Aquifer Exhibit in the Beverly S. Sheffield Education Center near Barton Springs Pool in Austin, TX, Figure 3.⁹ The top image shows a display representing natural waters impacted by (left to right): good stewardship, toxic chemicals, algae blooms, and erosion. The sign associated with the algae blooms notes that they can be stimulated by nitrate and phosphate contamination. The bottom image in Figure 3 shows a spectrophotometry simulation. Pushing a button on the map turns on the light associated with the oversized sample tube to simulate using a spectrophotometer to find the nitrate level for water at that location.

 

Figure 3. Exhibits from the Beverly S. Sheffield Education Center near Barton Springs Pool in Austin, TX. (TOP) Simulated water columns of varying water quality.(BOTTOM) Simulated spectrophotometry demonstration.

 

As noted earlier, plant life in the ocean require iron to thrive. This has led to studies of how addition of iron to the ocean, either through natural events like wildfires or volcanic eruptions, or though deliberate addition of iron by humans, can stimulate the growth of algae and other phytoplankton.¹⁰ The blooms of phytoplankton consume carbon dioxide. If the microorganisms sink into the ocean more quickly than they can decompose and rerelease the carbon dioxide, they provide a means to move carbon from the atmosphere to the bottom of the ocean. In the past, this process was considered for implementation at a very large scale as a geo-engineering approach to decreasing the concentration of carbon dioxide in our planet’s atmosphere, and thus possibly mitigating climate change and ocean acidification. This idea is controversial, but at least provides a springboard for many classroom discussions. These discussions can cover the chemical and physical aspects of the process: How much carbon dioxide can be removed? How much iron is needed? What are the efficiencies of removal? The discussions can also take on the economic and political aspects of the process: What are the costs of implementing large scale iron seeding of the oceans? Who is responsible for paying those costs? Even if we were to achieve exquisite control of turning this process on and off again, who is in charge of setting the planet’s thermostat?

 

What Algae Can Give

Algae plays an important role in taking in carbon dioxide gas and producing oxygen gas. For example, diatoms (described below) are credited with providing 20-30% of the oxygen in the air.¹¹ The relative amounts of the major gases in the Earth’s atmosphere can be illustrated by strips of colored tape placed on a stick divided into millimeters, Figure 4. The total length of colored tape is 760 mm, representing 760 mmHg or one atmosphere of pressure. On this scale,

• the white tape strip representing nitrogen gas is 593 mm long,
• the green tape strip representing oxygen gas is 159 mm long,
• the black marker ink on the tape representing argon gas is 9 mm long,
• and the yellow tape line on the tape representing carbon dioxide gas is 0.3 mm long.

This is reminiscent of the "LEGO Brick Atmosphere Sticks" described in a previous blog post.¹²

 

Figure 4. Meter stick marked with tape to illustrate the partial pressures of various gases in the Earth’s atmosphere

 

The amazing ability of water plants such as algae to photosynthetically produce oxygen gas can be seen in the bubbles that appear on plants in the water on a sunny day. One memorable experience I have had with gas bubbles on plants was during a visit to Barton Springs Pool in Austin, TX. On that very sunny day, when I stepped in the water weeds growing on the bottom of the pool the bubbles would rise up and tickle my legs, Figure 5. Though I did not actually test the gas to prove that was oxygen, there are a number of classroom experiments that have been developed to monitor oxygen gas production by illuminated plants in water.¹³

 

 

Figure 5. (LEFT) Barton Springs Pool in Austin, TX. (RIGHT) Gas bubbles rising up from aquatic plants in sunny Barton Springs Pool.

 

Some algae can produce diatomaceous earth. Diatoms are a form of algae that grow skeletons made of silicon dioxide.¹¹ Diatomaceous earth is composed of the remains of these skeletons. Although silicon dioxide is not very chemically reactive, diatomaceous earth can be used as a medium for filtering samples both within and outside of the chemistry laboratory. Figure 6 shows electron micrographs of diatomaceous earth (sometimes referred to as Celite) used for filtration in the chemistry laboratory. Note that most of the particles are broken algae skeletons. This is not very surprising, as macroscopic seashells are often found as fragments.

 

 

Figure 6. Electron micrographs of diatomaceous earth used for filtration in the chemistry laboratory

 

Other algae products include bioorganic products such as bio oils and alginate. At Bradley University, we cross-link alginate polymers with calcium ions as part of a greener pre-stoichiometry lab. This lab has been submitted for distribution through the organization Beyond Benign. We have also explored the use of alginate, rather than phosphate, for its interaction with divalent cations for possible use in a future “Radium Girls” lab (see a previous ChemEd X post, Online Activity: Chemical Kinetics and the “Radium Girls”.¹⁴ To conclude, our very existence on this planet is intertwined with algae, taking in light energy and various simple substances and producing a wealth of products. Algae is therefore a rich topic with many possible connections to the chemistry classroom.

 

Safety

Avoid directly looking directly into laser pointer as the intensity of the light produced may permanently damage eyesight. Avoid inhaling diatomaceous earth.

 

Acknowledgements

This work was supported by Bradley University and the Mund-Lagowski Department of Chemistry and Biochemistry with additional support from the Illinois Heartland Section of the American Chemical Society. The material contained in this document is based upon work supported by a National Aeronautics and Space Administration (NASA) grant or cooperative agreement. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author and do not necessarily reflect the views of NASA. This work was supported through a NASA grant awarded to the Illinois/NASA Space Grant Consortium.

 

References

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3. American Museum of Natural History. Creatures of Light: Nature’s Bioluminescence (accessed March, 2023).
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