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• TeachEngineering
• Grow Your Own Algae!

Hands-on Activity Grow Your Own Algae!

Grade Level: 8 (7-10)

(30 minutes set-up time; extends for 5-7 days)

Expendable Cost/Group: US $10.00

Group Size: 5

Activity Dependency: Biological Processes: Putting Microbes to Work

Subject Areas: Biology, Chemistry, Life Science, Science and Technology

NGSS Performance Expectations:

Activities Associated with this Lesson Units serve as guides to a particular content or subject area. Nested under units are lessons (in purple) and hands-on activities (in blue). Note that not all lessons and activities will exist under a unit, and instead may exist as "standalone" curriculum.

• Microbes Know How to Work!

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Engineering connection, learning objectives, materials list, more curriculum like this, introduction/motivation, vocabulary/definitions, troubleshooting tips, activity scaling, user comments & tips.

Environmental engineers play a critical role in protecting the environment and public health by developing wastewater treatment systems that use microbes to break down dangerous contaminants and pollutants. They must consider factors such as pH and temperature when they design systems to remove nutrients from wastewater.

After this activity, students should be able to:

• Explain how the amount of light that passes through a sample can be used to determine the growth of microbes.
• Demonstrate that algae consume nutrients dissolved in water.

Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .

Ngss: next generation science standards - science.

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International Technology and Engineering Educators Association - Technology

State standards, florida - science.

Each group needs:

• coffee filter
• fish tank or large glass container
• liquid plant fertilizer
• small plastic soda bottle (591 ml)
• larger mason jar

(Note to teacher: This activity was designed to help students understand how engineers use algae species to recover the nutrients found in wastewater. Students may be interested to know that some types of algae produce oils that can be processed to power cars and trucks.)

Here's our design challenge: You are an engineer given the task to develop a system for removing nutrients from a local stream. The stream is contaminated from rainwater that has picked up nutrients from the fertilizers used at a local golf course. You know that algae can naturally remove the nutrients when they are grown on nutrient-rich waters. You want to find algae species that are native to the area. Our activity focuses on finding the right species for the clean-up job. Ready to get started? Let's do it!

See the associated Biological Processes: Putting Microbes to Work lesson for information on biological processes. Focus on what occurs when wastewater enters natural water bodies.

Before the Activity

• Collect water samples at a local lake or river, 591 ml in each soda bottle, one for each student group.
• Filter each water sample through a coffee filter into the larger mason jars.
• Store the samples in the refrigerator until the activity is ready to start.

With the Students

• Have students fill the fish tank or glass container three-quarters of the way with tap water.
• Add 10 ml liquid fertilizer per liter of tap water.
• Add an additional 20 ml sample lake or river water per liter of tap water.
• Use a spoon to mix the contents in the tank.
• Place the container on a window sill or near some artificial lights.
• Observe changes in the tank over a few weeks.

After the Activity

The activity takes a few weeks to run its course. The algae species go through all the growth phases described in the associated lesson. Once the color of the tank starts turning anything other than green, end the activity by dumping the tanks contents down the drain or on grass.

microalgae: An organism similar to a microscopic plant. Like plants, they use the Sun's energy to grow while taking in carbon dioxide.

Pre-Activity Assessment

Questions : Ask the students and discuss as a class:

• How do the nutrients in wastewater affect microbes? (Answer: The microbes, like algae, use the nutrients to grow.)
• For the nutrient removal system you are developing, do you think the species that you are growing in the tank are suitable? (Answer: Selecting for local species is important because they can already compete with the other bacteria that live in the area. They are also already accustomed to the regional climate.)

Activity Embedded Assessment

Questions : Ask the students:

• What is in the water collected from the stream or lake? Why are we taking that water sample and putting it in the tank? (Answer: The water sample contains all sorts of organisms naturally present in water bodies. Usually these organisms are kept in check by natural limitations in nutrients, food sources and climate. Of these organisms, we are hoping to select for some algae species.)
• Why is the water turning green? (Answer: In large quantities, we can see algae in water because as the algae begin to thrive, they multiply and cause the water to turn green.)
• Near the end of the experiment: Why is the green color vanishing from the tank? (Answer: The nutrients in the tank have all been used up. Now the algae are starting to die.)

Post-Activity Assessment

• What tools can we use to measure growth? (Answer: Engineers use the color change as a way to measure growth. They send light through the container and measure how much is absorbed by all the cells. The more light that is absorbed, the more algae we have growing in the container.)

If the initial growth is anything other than green, it is advisable to end the experiment since it is possible that non-algal bacteria have colonized the tank.

• For ninth and tenth grade students, use this activity to model growth rates. For example, place a solar cell under the tank and connected to a voltmeter. As the algae begins to grow, take periodic measurements of how much light passes through the tank. Allow students to create a graph over time of the data they collect and have them explain why it might behave in a certain way.

Students learn the fundamentals of using microbes to treat wastewater. They discover how wastewater is generated and its primary constituents. Microbial metabolism, enzymes and bioreactors are explored to fully understand the primary processes occurring within organisms.

By studying key processes in the carbon cycle, such as photosynthesis, composting and anaerobic digestion, students learn how nature and engineers "biorecycle" carbon. Students are exposed to examples of how microbes play many roles in various systems to recycle organic materials and also learn how ...

Students gain an understanding of the parts of a plant, plant types and how they produce their own food from sunlight through photosynthesis. They learn how plants play an important part in maintaining a balanced environment in which the living organisms of the Earth survive. This lesson is part of ...

In a multi-week experiment, student teams gather biogas data from the mini-anaerobic digesters that they build to break down different types of food waste with microbes. Using plastic soda bottles for the mini-anaerobic digesters and gas measurement devices, they compare methane gas production from ...

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Algae experiments, ideas, and lesson plans.

Want to teach your students about algae? Here are some resources to help you!

Here are some Lesson Plans:

• Algae Growing   (Google document)
• Algae Bloom Investigation  (Google document)
• Algae Bloom Experiment  (Downloadable PDF)

Zooplankton project are really great too:

• Brainy Briny family of products

 Here are some videos:

 Additionally, feel free to join the algae community by following us on social media to collaborate and share your ideas and findings with other educators!

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• ChemMatters

From Pond Scum to Product: The Chemistry of Algae

by  Max G. Levy

Download Article (PDF)

Teacher's Guide (.docx)

Teacher's Guide (Google Doc)

Spanish Translation of Article (PDF)

The first time Beth Zotter tried her company’s bacon, it tasted bitter, and powdery. “Most protein concentrates don’t taste very well,” says Zotter, cofounder and chief executive officer of Umaro Foods. Umaro was attempting to re-create crispy, savory bacon out of seaweed.

Why bacon? “It’s America’s favorite food,” said co-founder Amanda Stiles on an episode of the TV show, “Shark Tank,” where the two raised funds for Umaro. “It’s the holy grail of plant-based meat. Sizzling, salty, delicious.” But the real magic of Umaro’s pitch was not the bacon. It was the algae.

Plant-based meats are often assembled from soy or pea protein. While algae are plant-like because they conduct photosynthesis with chloroplasts, they don’t have other roots or stems. And they actually photosynthesize far more efficiently than plants.

This holds true from microalgae (or phytoplankton), which are invisible to the naked eye, to enormous forests of seaweed in the ocean.

“Algae own the carbon cycle,” says Schonna Manning, a phycologist (one who studies algae) at Florida International University. “When it comes down to carbon sequestration, algae can sequester up to 400 times more than trees,” said Manning. Algae are an inherently more efficient biological machines for carbon capture than trees or plants, because their entire surface area is dedicated to photosynthesis, and they don’t waste resources creating trunks, roots, or branches. Algae just make more algae.

You might think of algae as the dark stuff on your sushi or the layer of green growth inside a forgotten water bottle. But their many species (up to one million) can be harvested and engineered into products that are not just useful, but better than what we use now.

“They’re really little green machines—or purple machines, or golden machines,” says Manning.

These biological machines have the tools to capture planet-warming carbon dioxide from the atmosphere, produce proteins and oils for human nutrition, biofuels, toxins that kill microbes, or miscellaneous vitamins and nutrients that support health.

“There are so many unique groups with all these different unique characteristics that we can exploit if we’re being creative as biologists and chemists and engineers,” said Manning.

Like Umaro, labs around the world have embraced algae as a material for the future. And they are confident that the world will soon depend on seaweed, and be better off as a result.

The Carbon Cycle

The carbon cycle is  nature’s way of recycling carbon atoms, which move from the atmosphere into living and nonliving things and then back into the atmosphere over and over again. For example, carbon dioxide is used by plants to make food, the food is eaten by land animals and given back to the atmosphere as they breathe out carbon dioxide.

Five Basic Tastes

Biology's First Supermaterial

The story of algae’s future promise reflects its ancient past. The oldest algal fossils date back more than one billion years. “Every four out of five breaths that you’re taking in, that oxygen is coming from microalgae not trees,” says Manning. “They’re really a foundation to oxygen and life on this planet.” 

Primitive algae were among the first organisms to sequester carbon from the atmosphere, which established their place at the base of the food web. 

Brown seaweed also provides us with a compound called alginate . Alginates are copolymers, or chains consisting of two different monomers: β-D-mannuronate (M) and α-L-guluronate (G).

Some sections of that chain feature a sequence of repeating α-L-guluronates, or repeating β-D-mannuronates with some sections alternating between the two.

What results is a gummy, edible polymer. Engineers commonly use alginates in cosmetics, fire-proofing materials, and as a food thickener.

“If you enjoy boba tea, you can thank those engineers because those are actually alginate-de-rived compounds,” says Janine Hutchison, a microbiologist with the Pacific Northwest National Laboratory.

Hutchison and her colleagues develop technologies based on algae and alginate. Last year, they reported creating “3D bio-ink” from alginate. This ink is colorful, lustrous, biocompatible, and can be printed at room temperature, an ideal trait for many applications.

Scientists want to print human tissue in specific three-dimensional shapes. The reason is that real human tissue exists in 3D networks, yet most conventional studies are ducted in 2D Petri dishes.

Cells cultured on three dimensional “scaffolds” behave more like the real thing. It’s better to print human neurons in a small, interconnected sphere than a flat sheet, for example.

Pharmaceutical experiments on these models will better predict actual human responses to new medicines. It’s worth noting that agar and agarose gels used for 2D experiments also come from algae!

“We have been hindered in 3D-printing technologies by relying on plastics,” says Hutchison. 

Plastics must be heated to 240 ºC (464 °F) to be able to melt for extrusion.

“There’s no way a living cell, or any biological component can survive that type of heat or stress, even for a short duration of time,” said Hutchison. Alginate is more amenable to biofriendly conditions, so human cells will grow on structures made of alginate.

World Oxygen Production

A Sense for the Future

Algae expands the limits of what people can sense, too. In fact, seaweed is the reason why we discovered a fifth taste.

In 1907, a Japanese woman named Tei Ikeda prepared boiled tofu in a kelp broth called kombu dashi. Dashi had long been a staple of Japanese cooking. But that day, Tei’s husband Kikunae tasted the broth and had a realization: There is a taste here that is distinct from sweet, salty, bitter, and sour.

The broth was rich and savory, almost meaty. Kikunae, a chemist, then isolated crystals responsible for the mysterious flavor he named “umami” (translating loosely to “deliciousness”). He discovered that glutamic acid, one of the most common amino acids, was responsible for the taste of umami.  He would eventually isolate monosodium glutamate (MSG) which would be sold as a seasoning product for umami.

Umami is now recognized as our fifth taste. It gives us a name to explain why some foods are so good. Ripe tomatoes, egg yolks, aged cheeses such as parmesan, seaweeds such as nori, and cured meats such as bacon, all contain glutamates.

Given this history—and chemistry—it makes sense that Zotter would mimic bacon with seaweed. Meat production accounts for nearly 60% of global greenhouse gas emissions in agriculture, so reducing or replacing it has become a popular approach among people who want to minimize their carbon footprint.

The demand for meat substitutes continues to grow and companies, such as Beyond Meat and Impossible Foods, have led the way with plant-based burgers and ground meats. “Give a lot of credit to the founders of those companies for saying we can make meat replacements from plants,” Zotter says.

But other meats, such as bacon, have been harder to replicate with the usual ingredients. “Right now, we basically have soy, and we have legumes. And some people are now producing using fungi,” she adds.

“We need more options. And the ocean just seems like a no brainer,” said Zotter.

The ocean is an obvious target, according to Zotter, because of nitrogen. Nitrogen is an essential element for life. It’s what gives amino acids their name (from nitrogenous “amine” -NH 3 + groups), and snaps them together like Lego pieces to create all proteins.

While gaseous diatomic nitrogen makes up 78% of our air, it’s not chemically reactive nor available for most land plants to process. Oceans contain the largest reservoir of chemically reactive nitrogen on Earth.

“Oceans are huge, and we can make protein without freshwater. The resource potential is enormous,” says Zotter.

Umaro Foods successfully isolated the protein from nori, a protein-rich red algae used on sushi rolls, but bacon is more than just protein. It’s the fat and flavor that sets bacon it apart.

Bacon fat is solid at room temperature, so Zotter’s team found that, when nori protein is combined with algal components agar and carra-geenan it behaves the same as bacon.

Both compounds are hydrocolloids, meaning they form gels with water. They come from gracilaria and kappaphycus species of algae, respectively. These seaweed-based ingredients are able to encapsulate plant-based oils into a fat that crisps and crunches just like the animal fat of bacon. Then, after much trial and error, Umaro Foods developed a flavor recipe to match bacon’s flavor and complement nori’s natural umami.

They debuted their crispy bacon prototype on “Shark Tank,” and now offer it at select restaurants around the United States. Zotter says, “Our vision is that seaweed is the most scalable, lowest cost, and will be the most abundant protein. It’s almost inevitable.”

Re-Greening the World

While algal proteins could reshape the energy in our diets, algal oils could change the fuels that power our machines. Microalgae can reach 50% oil content, by weight, and 25% protein. They are also entirely photosynthetic.

Compare that to a tree that is covered in non-photosynthetic brown bark. This means algae can produce energy efficiently, while simultaneously extracting carbon dioxide from the atmosphere.

Research organizations have wanted to harness algal oils to make fuels, such as jet fuel, for decades, and Dave Hazlebeck, founder of Global Algae, has been a part of this endeavor for nearly 20 years.

Hazlebeck led the biofuels research for an energy company called General Atomics. He steered a consortium of 30 companies in a government-funded program to create jet fuel from algae.

“Through that I became fully aware of all the challenges, all the issues, all the opportunities with algae,” he says. That program ended for the government, but not for Hazlebeck. “I wanted to stay in algae because of the potential of what it could do for the world,” said Hazlebeck.

During the past nine years, Hazlebeck’s Global Algae developed technology to farm and harvest microalgae, and to extract their oils and protein.

They figured out how to cultivate large ponds of microalgae outdoors without contamination from bacteria, viruses, or undesirable algae. Their harvesting system uses 100 times less energy than previous systems.

Each innovation has brought down the cost of producing algae, its oils, and protein, so that it can compete with existing crops such as soy, corn, and palm oil. Existing plant crop farms create problems for the planet—problems that algae may actually solve.

Corn and soy require precious supplies of fresh-water and farmland; the world’s growing reliance on inexpensive palm oil has increased deforestation. Algae farms could replace palm plantations.

And according to Hazlebeck, algal oils are so similar to palm oil, that they can be processed by the same mills. Microalgae are actually richer in omega-3 fats, which could be sold as a separate product.

“You can allow most of the rainforests to regrow, because we can produce almost 10 times as much oil per acre,” Hazlebeck says.

Some of the algae oil would be processed to make jet fuel, and they could isolate the protein from each harvest, too. “About 15 times more than if you were doing soy there,” according to Hazlebeck.

He imagines that protein could feed livestock or fish farms. Each product sets Global Algae up to replace the status quo with alternatives that reduce greenhouse gas emissions. And Hazle-beck also believes algae will help remove carbon dioxide already in the atmosphere.

The idea begins with algae capturing CO 2 during photosynthesis. If you make those photosynthetic products into fuel and food, which then get burned or digested, that carbon goes right back into the atmosphere. That’s not a good carbon-se-questration strategy.

But if you turn some of the organic matter from algae into plastics, the carbon will stay trapped for a very long time. Plus, most of the world’s plastic production comes from fossil fuels.

Next, Global Algae plans to use revenue from their products to buy and protect rainforests. Those land buys would just factor into their costs. “It would be an economically viable approach,” Hazlebeck says.

Last year, Global Algae won a $1 million prize by being a finalist in a carbon-capture tech competition led by the nonprofit XPrize. “That was a great honor and helps us by opening doors to move things faster,” says Hazlebeck.

“If we were on an accelerated timeline, we could probably stop deforestation by approximately 2032, and probably have it completely reversed by 2040,” Hazlebeck says.

The final round of demonstrations for XPrize’s carbon-capture contest is in 2025. In the meantime, Global Algae plans to operate a new farm in California and continue refining its extraction technology. The grand prize is $50 million.

Whether you’re interested in inks, plastics, fuel, or food, algae is sneaking into the conversation. The phycologist Manning notes algae’s potential in medicines that combat bacteria, viruses, or even cancer. Many drugs in your medicine cabinet came from plants discovered in rainforests.

Algae’s chemical secrets may also reveal some superpowers. Preliminary studies show that com-pounds isolated from algae can kill drug-resistant pathogens. “Kind of a neo-Neosporin,” says Manning, “Algae don’t have teeth and claws, so they’re producing a lot of these different compounds as a defense. They’re usually just trying to claim their space in the world.”

And algae’s space in the world appears to be on the cusp of a major expansion.

https://www.xprize.org/prizes/carbon/articles/this-algae-eats-co2-from-the-atmosphere 

Yong, E. The Origin Story of Animals Is a Song of Fire and Ice. The Atlantic, Aug 16, 2017: https://www.theatlantic.com/science/archive/2017/08/theanimal-origin-story-is-a-song-of-ice-and-fire/537003/ [accessed Feb 2023].

Zimmer, C. How Did Plants Conquer Land? These Humble Algae Hold Clues. The New York Times, Nov 19, 2019: https://www.nytimes.com/2019/11/14/science/plant-genes-evolution.html [accessed Feb 2023].

Cabrera, J. Innovators Develop Seaweed-Based Alternatives to Plastic Food Wrappers. Mongabay, Jan 17, 2023: https://news.mongabay.com/2023/01/innovators-develop-seaweed-based-alternatives-to-plastic-food-wrappers/ [accessed Feb 2023].

Oster, L. Is Seaweed the Next Big Alternative to Meat? Smithsonian magazine, June 23, 2022: https://www.smithsonianmag.com/innovation/is-seaweedthe-next-big-alternative-to-meat-180980299/ [accessed Feb 2023].

Max G. Levy is a freelance science journalist based in Los Angeles, Calif., writing about tiny neurons, vast cosmos, and all the science in between. He received a Ph.D. in chemical and biological engineering from the University of Colorado, Boulder.

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The Algae-in-a-Bottle Experiment: A High-Impact Learning Activity

This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

For more information about the peer review process itself, please see https://serc.carleton.edu/teachearth/activity_review.html .

• First Publication: December 22, 2015
• Reviewed: December 10, 2020 -- Reviewed by the On the Cutting Edge Activity Review Process

The Algae-in-a-Bottle Experiment provides an engaging and flexible high-impact teaching tool for helping students to know, understand, and apply a number of concepts related to the biology and ecology of aquatic plants and their environments. It is also relevant to methods being developed for the use of algae as an alternative energy source, that is, biofuels. The protocols in this experiment can be adapted use as a demonstration activity in one or two class sessions, or as a nature of science, inquiry-based activity over a few to several weeks. The easy-to-obtain and inexpensive materials used in the experiment make it accessible to institutions where resources and space are limited, as long as sunlight or artificial light are available to carry out the experiment. Preliminary results with non-majors enrolled in introductory general education oceanography courses in a community college indicate increased engagement and a high level of enthusiasm for the experiments, and suggest a better knowledge and understanding of the effects of light and nutrients on photosynthesis, and greater appreciation for the nature of science. We believe that the Algae-in-a-Bottle Experiment offers an effective means for improving science literacy and for introducing scientific research to diverse learners from middle school to college.

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‘Algal balls’ – Photosynthesis using algae wrapped in jelly balls

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Photosynthesis can be a hard topic to demonstrate reliably in the lab, especially in winter. This fun and reliable practical makes investigating photosynthesis easy, with a technique that can be used with students from KS3 to post-16, and offering quantifiable and replicable results.

This page includes the core information on the protocol and the students’ notes for 11-16 students. For post-16 students, please see our  updated post-16 notes .

Algae  (Scenedesmus quadricauda)  can be purchased from our recommended suppliers, Darwin Biological and Blades Biological . We suggest that a 30ml sample will need to be grown for 2-3 weeks using the growth medium recipe to ensure there is a sufficient amount for a class of 30. Please note that the algae can be purchased from other school suppliers.

Green algae photosynthesise in a way similar to that seen in C 3  higher plants. In this practical, students use algae to look at the rate of photosynthesis. Since algae are tiny and are difficult to work with directly in the water,  the first part of the practical involves ‘immobilising’ the algae as algal balls. This effectively traps large numbers of algal cells in ‘jelly like’ balls made of sodium alginate. Sodium alginate is not harmful to the algae, and they will continue to photosynthesise once immobilised.

When these algae are ‘wrapped up’ in the jelly balls they are excellent to use in experiments on photosynthesis. These algal balls are:

• cheap to grow and easy to make – you will be able to make hundreds in a very short time
• easy to get a standard quantity of plant material because each of the balls is approximately the same volume
• easy to keep alive for several weeks so you can keep them for future experiments

A kit, produced in collaboration with the NCBE , is available for this practical.

Further details  to support those doing further investigations with this protocol with post-16 students are also available.

See what has been said about the resource

"Straightforward advice offering an alternative to pondweed photosynthesis."

What's included?

• SAPS - Colour chart showing hydrogencarbonate indicator
• SAPS - Photosynthesis with Algal Balls - Student Sheet
• SAPS - Photosynthesis with algal balls - Algal growth medium recipe
• SAPS - Photosynthesis with Algal Balls - Student Preparation Sheet
• SAPS - Photosynthesis with Algal Balls - Teaching Notes
• SAPS - Photosynthesis with Algal Balls - Technical Notes
• SAPS Sheet 23 - Photosynthesis with Algal balls
• SAPS - Photosynthesis context
• SAPS - Photosynthesis - context notes
• Photosynthesis
• Respiration
• Essential practicals

Related content

Teaching resources.

• 'Algal balls' - Investigating photosynthesis and respiration: post-16 version
• A-level set practicals - factors affecting rates of photosynthesis
• Photosynthesis: testing a variegated leaf for starch
• Photosynthesis Quiz: Test Your Knowledge!
• Biology animations - transport of water and sugar, respiration and photosynthesis and cell growth in plants

Episodes - Lessons

Chemistry & biology of algal blooms, full episode, classroom videos.

Did you ever try to eat an entire apple pie chased with a quart of milk? If so, you how too much of a good thing can create problems. It’s the same with algae.

In many lakes and oceans, algae is an important part of the base of the entire food pyramid in naturally balanced ecosystems. But when algae is artificially over-fertilized in an unbalanced ecosystem, it can create waaaay too much of a good thing. And that can make things go horribly wrong.

Take Tainter Lake for instance . It’s located in northwestern Wisconsin and was once a pristine home to a number of bird, fish, reptile, and amphibian species. But nowadays, an organism known as blue-green algae typically forms a slimy mat over the lake during the summer. It not only stinks and prevents people from recreating on the lake, the toxic algae reportedly causes health problems for the lakeside residents. So what’s happening here?

As you’ll see in the video, our eco-investigator, Caroline, met with residents and scientists to discover how blue-green algae forms cyanobacteria each summer, which in turn, produce toxins. These toxins have caused health problems, such as lupus-like symptoms and hives for some residents.

To understand the causes of this environmental problem, we need to look at the basic chemistry and biology of plant and algae growth. Farmers put un-natural amounts of phosphorous (P) and nitrogen (N) on their fields to grow maximum crop yields. Those plant nutrients are often a combination of commercial fertilizers and animal manure. Unfortunately, rains wash off some of those fertilizers from the landscape and the mix ends up in rivers and lakes.

So the main cause for this toxic algal growth at Tainter Lake is the increasing concentration of “plant nutrients” getting washed into the lake. Phosphorous is one of the biggies, that’s contained in the fertilizers that modern farmers apply on their fields, and is a major chemical component of cow manure . Depending on a number of variables such as slope, rainfall, runoff, concentration, soil attachment, and erosion, both sources of phosphorous and nitrogen can get flushed off fields, into streams, and ultimately into lakes such as Tainter. So these forms of fertilizer that cause field crops to grow also functions the same way in the lake, except that it can cause a massive undesired algal bloom. Though not technically a plant, algae uses the same plant-like process of photosynthesis to grow and thrive. And when all that algae begins to die off, it causes depletion of the oxygen content in the water that can kill off aquatic life, creating a "dead zone". To learn more about how nutrient-induced algae causes hypoxic zones, check out the NOAA link below.

So what’s to be done? Society needs farmers to grow crops, right? Well, for starters farmers can limit how much phosphorous and nitrogen gets washed off their fields in a couple of ways. One is by limiting the amount of fertilizers they use on their crops. This is done through what is called “nutrient management planning”. In short, they only apply what the crops can absorb and use to grow. As you might imagine that depends on a number of technical things and the forces of Mother Nature. Another way to limit phosphorous and nitrogen runoff is by using improved farming techniques that help prevent excess nutrients from leaving the soils and landscape. To learn more how this is done, take a moment and watch the video.

To really “plow into” the science and environmental implications of all this, and ignite the chemistry and biology parts of your brain:

• Explore the extended learning section below by clicking on the " Learn More " tab below.
• Or better yet, ask your teacher to download the lessons below so your entire classroom can share in peer-driven learning. Now we're talkin' serious fun.

Also, find out more about what you can do to keep your local waters healthy and clean by checking out the website of our educational partner, Wisconsin Land+Water.

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Teen’s algae-biofuel experiment wins science fest

Teen’s Algae-Biofuel Experiment Wins Science Fest The winner of the $100,000 Intel Science Talent Search is Sarah Volz, a Colorado public high-school senior who developed a way to increase oil yields from algae, a potential alternative to fossil fuels .

Discussion Ideas:

• Watch this 2:30-minute video on algal fuel , how it is cultivated, and why it is an important potential fuel source in the United States. Based on the description of the experiment in the NBCNews article above , what part of the cultivation process do students think Sarah’s work addresses? (Her experiments focused on targeting lipid-rich algae cells, a process explained at about 1:10 minutes into the video clip.)
• The video does not address any drawbacks to developing algae as a fuel source. Read the relevant part of our encyclopedic entry on biomass energy. What are some obstacles to developing algae as a fuel source? (It is an expensive process, especially the start-up costs associated with building an algae ‘refinery.’)
• Almost all industrial  producers of algal fuel are in developed nations. Can students suggest some reasons why? (It’s expensive, and the process requires a tech-based infrastructure (including education and economic incentives) that most developing nations do not have.)
• Do students think the United States should invest in developing algal fuel as an complementary or alternative to fossil fuels? Why? If yes, do they think the financial investment should come from the government (through taxes and other revenue) or from private investment? Why? (Currently, both the Department of Energy (government) and private industry (such as Chevron ) are investing in experimental algal fuel technology.)
• Algae is just one source of biomass energy. What are some other sources of biomass energy ? (Trees, food crops such as corn and soy, and municipal waste—garbage—are some leading sources of biomass energy.)

Note: We’re experimenting with a new feature here on the NG Education Blog. “Current Event Connection” posts will connect educators with news stories and relevant discussion ideas featuring content from the NG Education website. 

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3 thoughts on “ Teen’s algae-biofuel experiment wins science fest ”

• Pingback: Truly Alternative Energies: Biopower | Nat Geo Education Blog
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Reassuring educational article on Algae bio-fuel experiment. Hopefully this progresses quickly and becomes a reality. I guess, we must be careful not to exhaust the planets’ resources as we dicover them and begin to make use/abuse of the benefits to our ever growing capacity to consume more than ou neighbour. .

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Science project, growing algae.

Grade Level: 6th - 12th; Type: Life Science, Engineering

This project measures the growth rate of algae supplied with supplemental carbon dioxide.

The goal is to have the student conduct a controlled experiment to test a hypothesis about conditions affecting the growth of algae.

Research Questions:

• Does supplemental carbon dioxide affect the growth rate of algae?
• Is the experimental design capable of producing enough carbon dioxide to drive algal growth?

Algae are organisms commonly found in aquatic environments. There are two types: macroalgae and microalgae. The large multicellular macroalgae are often found in ponds and in the ocean. They tend to be measurable in inches, although giant kelp in the ocean can grow to more than 100 feet in length. Microalgae are tiny unicellular algae that grow as suspensions in water; they are measurable in micrometers. Common sources of microalgae are bogs, marshes, and swamps.

All algae require sunlight, water, nutrients, and carbon dioxide for growth. Through the process of photosynthesis, algae convert the carbon dioxide into glucose (a sugar). The glucose is then broken down into fatty acids, which under normal conditions, are used to produce membranes for new algal cells. If, however, the algae are starved of nutrients, the fatty acids produce fat molecules (oil). Because carbon dioxide is the only source of carbon for algae, having an adequate supply is essential if they are to be used for commercial purposes.

• What materials are required? Three one-liter bottles of purified water; sugar; brewer’s yeast; silicone sealant; drill; 6-mm aquarium airline tubing; algae
• Materials can be found at the following places: Purified water (supermarket), sugar (supermarket), brewer’s yeast (supermarket), silicone sealant (Walmart-type store); aquarium; airline (pet store); algae (pond or marsh or biological/scientific supply house); 10-15-10 liquid plant food (plant nursery or Internet)

Experimental Procedure:

• Read about the conditions required for algae to grow, and formulate a hypothesis to predict whether giving algae supplemental carbon dioxide would be a feasible way to increase algae growth.
• Collect some algae from a pond, marsh, swamp, swimming pool, fish aquarium, bird bath, or other source. If you are unable to locate a natural source, contact a biological/scientific supply house (Google).
• Add equivalent amounts of algae to two (clear plastic) bottles of purified water. Discard the bottle caps.
• Add two drops of 10-15-10 liquid plant food to each bottle.
• Pour out a small amount of water from a third bottle of purified water, leaving about an inch of air space at the top of the bottle. This bottle will be the carbon dioxide reactor.
• Make a hole in the bottle cap of the reactor bottle that is just large enough to allow an aquarium airline to pass through it, then run the airline through the hole so that it extends into the free air space when the cap is on. Seal the airline to the top of the bottle cap with a silicone sealant.
• Dissolve 2 teaspoons of sugar and 1 teaspoon of brewers yeast in the reactor. (Yeast is a fungus that converts sugar into carbon dioxide bubbles.)
• Extend the aquarium airline from the reactor bottle to one of the bottles containing algae. The airline should extend about half way into the algae bottle.
• Place all three bottles outdoors where they will get indirect sun. (TIP: Direct sunlight may inhibit growth. The optimum temperature for algal growth is between 20 and 24 degrees C. Temperatures above 35 degrees C are lethal to algae.)
• Monitor the growth of the algae in the two sample bottles for one month. If necessary, replace the sugar, yeast, and water in the reactor to keep the carbon dioxide source operating.
• At the end of the month, compare the amounts of algae in the two sample bottles.
• Evaluate your hypothesis in light of your findings. Revise it if necessary and propose additional experiments.

Terms: Photosynthesis; Algae; Microalgae; Macroalgae; Carbon dioxide; Yeast; Sugar

References:

• http://www.pbs.org/wgbh/nova/tech/algae-biodiesel.html
• http://www.nytimes.com/2009/06/29/business/energy-environment/29biofuel.html
• http://www.sciencedaily.com/releases/2008/08/080818184434.htm
• https://folk.ntnu.no/skoge/prost/proceedings/aiche-2008/data/papers/P125838.pdf
• http://www.slideshare.net/kabronic/maximization-of-algae-lipid-yield-scenedesmus-dimorphus-for-the-production-of-biodiesel
• http://www.qsl.net/w2wdx/aquaria/diyco2.html

Related learning resources

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• F.A.Q.s & Support

Family-Style Homeschooling

Algae and Pollution Experiment

This experiment is for all ages, as the colored smilies show. You can do the algae and pollution experiment with your whole family together!

The algae and pollution experiment is a Biology experiment from the Layers of Learning Ecology unit. Layers of Learning has hands-on experiments in every unit of this family-friendly curriculum. Learn more about Layers of Learning .

Algae grows naturally in ponds and is a normal part of the ecosystem of a pond. However, certain pollutants can affect the growth of algae. Phosphorus is one of the most important nutrients for plant growth, but if too much phosphorus makes its way into a pond, river, or lake, it can cause the algae and other aquatic plants to explode in growth. They use up all the oxygen in the water and suffocate out other life forms like frogs and fish.

Acid rain is another problematic pollutant. If the pH level is outside of the normal range in water, then it kills off the algae and other living things.

Step 1: Library Research

Before you begin exploring, read a book or two about pollution. Here are some suggestions, but if you can’t find these, look for books at your library about pollution, water pollution, conservation, and phosphates. The colored smilies above each book tell you what age level they’re recommended for.

As Amazon affiliates, the recommended books and products below kick back a tiny percentage of your purchase to us. It doesn’t affect your cost and it helps us run our website. We thank you!

You Wouldn’t Want To Live Without Clean Water!

by Roger Canavan

My River: Cleaning Up the LaHave River

by Stella Bowles

by Dan Fagin

Step 2: Algae and Pollution Experiment

WARNING: This experiment uses chemicals that can be dangerous if handled incorrectly. Keep out of reach of small children, wear gloves when handling chemicals, and never mix two chemicals together.

For this experiment you need jars, pond water, chemicals containing phosphates like detergents or fertilizer, and vinegar, which is an acid.

Before you begin this experiment get the scientific method worksheet and use this process to set up your experiment.

Collect two or more jars and add pond water to each jar to the same level. If you can actually see some larger patches of algae to scoop up, it will sure help the process to be quicker.

Let it sit in a sunny spot for a week to get growing.

Label one jar “Control” and leave it chemical free. It will be the jar you compare your others to.

At this point you are going to design your own experiment with the chemicals you want to use. You can use phosphate-containing chemicals to see how phosphates affect the growth of algae or you can use vinegar to see how acid rain might affect the growth of algae. If there are other common pollutants you are concerned about, you can try those in your experiment jars too.

Add only one chemical per jar. DO NOT MIX CHEMICALS WITH EACH OTHER!

Here are some choices to add to your jars.

• Laundry or dishwasher detergent with phosphates
• Laundry or dishwasher detergent without phosphates (to test against phosphate detergents to see if it is the phosphates that are making the difference).

Be sure to properly label the jars then set them in a place with warmth and sunlight for 1-2 more weeks and observe the growth.

You can observe the different amounts of growth by eye and even observe some of the algae that is too small for the naked eye under a microscope by placing a drop on a slide and observing it. You can also watch for color changes or density changes within the samples.

Which conditions created greater algae growth? Which created less? What does this tell you about the effect of things like fertilizer and detergent pollution? Acid rain? What affect does rampant algae growth have on a pond or a lake environment? What does too little algae growth mean for a pond or lake environment? Do you think all types of algae would respond the same way to pollutants that your variety did?

Step 3: Show What You Know

Complete your scientific method worksheet . On the back side make some notes about how you would adjust the experiment next time or further experiments you could make.

Additional Layers

Additional Layers are extra activities you can do or tangents you can take off on. You will find them in the sidebars of each Layers of Learning unit . They are optional, so just choose what interests you.

Deep Thoughts

Did you go into the experiment with expectations of what would happen?  Real scientists do too.  It’s called a hypothesis. 

Good scientists don’t let their hypothesis get in the way of the truth though.  If their experiment proves them wrong they’ll change their minds.

How did you control for bias in your experiment? Can you redesign the experiment to be even more fair?

Additional Layer

How does a city sewage system work?  How might pollutants leak from your home into ponds and lakes in your area from the city sewage? 

What if you live in the suburbs or country and have a septic tank?  How can pollutants affect the area then?

Scientists and entrepreneurs are looking at using certain types of algae to produce bio-fuels.  Research more about this.

Free Samples

Try family-style homeschooling now with free samples of four Layers of Learning units when you subscribe. You'll get to try family-style history, geography, science, and arts with your children.

You can unsubscribe any time.

54 thoughts on “Algae and Pollution Experiment”

Is a T a tablespoon or teaspoon?

Capital T is tablespoon.

This is not a detailed idea for an experiment. It is not this simple. Algae will not survive with simply scooping up pond water and sitting it outside. Waste of time.

Yes, algae will survive if it is in sunlight, at least for the few days or weeks required for the experiment. Also, the details of the experiment are purposely left up to the child. Part of this lesson is learning to think independently and creatively as opposed to following a recipe.

Hi there! I’m doing a research project on How pollution affects algae, and I was hoping if you could possible elaborate more on how pollution effects algae and it’s environment. Great experiment by the way!

Hi Diana, there is tons of research about how algae growth is an indicator of pollution. Here is one article to get you started: http://www.walpa.org/waterline/june-2012/algae-can-function-as-indicators-of-water-pollution/ . There are many kinds of algae and many kinds and amounts of pollution, so the specifics will vary, but in general, as algae has specific growing requirements, you can observe how algae growth is either rampant or stunted by what is present within the water it is growing in. We recommend that you look up several scholarly journals that detail ecological experiments dealing with pollution’s effect on algae growth. This is a topic that is easy to find. Best of luck on your project.

Can you please clarify what detergent does/does not have phosphate? thank you

Just read the labels. They will say if they have phosphates. If they do not have phosphates they are usually labeled “phosphate free”. In some places phosphates are illegal (Washington State is one I know of) in laundry detergent, so you won’t find them on grocery shelves.

If you’re still on the topic, I did a lot of looking for detergent with phosphates and I found that phosphates have been banned from detergent because they promote algae growth. This ban caused literally every company to remove phosphates from dish soap, detergent, hand soap, and basically any soap you can find. Luckily, if I did my research correctly, you can just buy trisodium phosphate (TSP) which is marketed as a “heavy duty” all purpose cleaner from home depot for about $7.

Yes, phosphates became banned in several states in the US and so manufacturers have changed their formulas. Dishwasher soap still often has phosphates because the bans applied primarily to laundry soaps. Thanks for your tip.

How do you measure or weigh the algae growth?

You won’t be measuring it quantitatively. You will observe the growth. As your algae grows, it will become more and more compact inside the container. As the algae population gets more dense, it also becomes more opaque. You will visibly see growth and may see color changes, depending on the type of algae you collected. You can also put a sample drop of water on a microscope slide for a view of some of the algae that is present but too small to see with the naked eye.

Could we use plant lights instead of placing the jars outside?

Yes, that should work well.

When you scoop the water, do you need to make sure algae is collected, too?

Not necessarily. The pond water will contain organisms too small for you to see and then you can watch it grow. However, if you can begin with some visible algae, it will speed up the process and be easier and quicker to observe.

Thank you . I really needed help in an activity. i didn’t have much ideas. you all helped it a lot. get going. Doing a great job guys.

Will the algae be in the water in cold weather still? I don’t mean in the dead of winter, but around Halloween?

Is algae still alive in pond water around Halloween in Central Maine? The temperature is about 45-60 degrees Fahrenheit.

Algae probably isn’t actively growing at this time of year, but if you collect pond water and bring it indoors to a warmer temperature it should take off and begin to grow.

How can I expand on the experiment? What could I use as a hypothesis?

You could hypothesize about the effects of any variety of specific chemicals on algae growth. Your hypothesis would include what you predict would happen specifically when the algae is exposed to a particular contaminant.

Ok, thank you!

What are the measurements for these? How much water and how much algae do I use for this experiment to get good results?

Exact measurements aren’t important. Just fill the jar most of the way and capture some algae, even a little algae will grow to much more in a few days if given sunlight.

How much pollutant should I add to two cups of water?

I would add about a tablespoon, but you can design the experiment however you like.

Does the container have to remain open, and is it okay to leave it inside by a window? or does it have to be outside?

The container should be left open and it can be inside. It just needs to have light, so in a window sill is perfect.

Okay, thank you!

Would the “pollutants” be the vinegar, bone meal, and fertilizer?

The specific pollutants you use are up to you, but those are a few ideas. You can just do one jar with one of the pollutants recommended, or you can use several jars, each with one pollutant. For example, you may have one jar with water and algae that you add fertilizer to while you have another jar with water and algae that you add vinegar to. In addition, make sure to keep one control jar that you haven’t polluted at all. You will be comparing the algae growth between the jars.

whats the conclusion of this experiment meant to be? Like what will I find after doing this experiment?

The nature of an experiment is that you have to do it to find out. Otherwise it is a recipe.

How much Bone meal and other stuff like that do i put in the pond water ?

Chloe, it’s up to you. You are the experimenter. You can approach this in different ways. If you want to simulate a real polluted body of water, then you need to do research to find out how many parts per million of pollutant is in the pond or lake, then figure out how much you would need from that.

If you just want to see what kind of general effect the pollutant has on growth, then as long as you carefully measure and keep your data records, then you can use your judgement. It might also be cool to try several different concentrations of the same pollutant in multiple jars instead of trying different pollutants in each jar. For example, you could try 1 gram, 2 grams, and 3 grams of bone meal in three different jars.

okay thank you! I also forgot to ask another thing, would I be able to use creek water because i have one by my home.

is karen the maker of the layer of learning? i need this infomation for my science fair project

Michelle Copher and Karen Loutzenhiser are the authors of Layers of Learning.

How long will it take for the algae to appear im doing an experiment about this for school and it needs to be done by a certain time.

That really depends on the type of algae you collected, the temperature of the water and air, and other factors. We could begin to see growth within a week and had significant growth in about a two weeks, but it’s dependent on your conditions. Good luck!

does it have to be pond water or would i be able to use something like salt water

It needs to be pond water. You are collecting microorganisms along with the pond water.

How many days do we have to let it sit out until it observes growth.

This is meant to be an experiment, not a recipe. You are the scientist. You set the parameters for the test. A minimum would be a week, but longer is better.

This experiment makes no sense at all. I can’t get the 1 qt jars cause they cost to much. And i can’t use pond water/

You can use any jars including those that you save from food packaging, like peanut butter or jam jars.

Why does it need to be pond water instead of distilled water

You have to have algae from pond water plus the things the algae eats that are in the pond water. You are testing natural waters and the effect pollution has on them.

Can you tell me the exact measurements for each material you used because I have a science fair coming up and I need the measurements for my project.

Hi Anne, There aren’t any specific measurements required. You will need to measure your own experiment and use those measurements. This same experiment has been done many times and in many ways. You will need to decide how much pond water you want in each jar (making it the same in each one) and then decide which pollutants you want to experiment with. As long as you track what you use, it will be an accurate experiment. A friend of ours is an environmental scientist and he goes around to ponds, lakes, and rivers all over our regions conducting this exact same experiment over and over again each year. This is what real scientists do to see the effects of pollutants on aquatic environments. Good luck!

Do you need to keep the lids off of the jars? Is oxygen needed for algae growth? Thank you for this experiment. We’re going to start it at the library next week for an Earth Day program.

Plants require carbon dioxide for photosynthesis and the algae will do better with the lids off. But it would be a good experiment to have a jar with the lid on and one with the lid off and everything else the same.

That’s a great idea. Though not sure if I have another jar. But if I do, I’ll try it! Thank you so much.

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• 11 April 2024
• Correction 23 April 2024

Scientists discover first algae that can fix nitrogen — thanks to a tiny cell structure

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Researchers have discovered a type of organelle, a fundamental cellular structure, that can turn nitrogen gas into a form that is useful for cell growth.

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Correction 23 April 2024 : An earlier version of this article omitted a reference to a previous study describing a genetic analysis of when ancestors of algae and bacteria entered a symbiotic relationship.

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Algae String

Introduction 

We use plastic objects every day. But what is plastic? If we zoomed in for a closer look, we'd see that it’s made of lots of long molecule chains called polymers. Most of today's plastics are made in a lab and not environmentally friendly, but nature can make useful polymers too! For example, natural rubber and paper are both created from natural polymers that are biodegradable. In this activity you will use polymers made by algae and a bit of chemistry to create your own custom string! 

Design Challenge

Create your own colorful string creations using ingredients that come from algae. Then craft fun things with your string! 

Biodesign, Chemistry, Materials Science

Make algae gel: 20 min

Let gel rest: 1 hr- overnight

Make calcium bath: 5 min

Make string: 30 min

Key Concepts

Polymers, chemical reactions, biomaterials, fiber arts

This activity was made possible by a Science Education Partnership Award (SEPA), Grant Number R25 GM129220, from the National Institutes of Health (NIH). 

Getting Started

Learn more with our videos.

What’s the Chemistry?

How Dried String Changes

Algae String Ideas

Make String From Algae

Learn more with our pdf guides.

Algae String Activity Guide

Follow this guide to turn powdered algae into a string using chemistry!

Algae String Essential Questions

Get answers to some of the sticky questions frequently asked by adults.

Algae String Tool Chest

The inside scoop on how different tools might affect your gel or string.

Algae String Mizuhiki Knots

Try these simple instructions to tie your own decorative Japanese knots.

If you think this looks fun, wait ‘til you try these!

Practical Biology

A collection of experiments that demonstrate biological concepts and processes.

Observing earthworm locomotion

Practical Work for Learning

Published experiments

Investigating photosynthesis using immobilised algae, class practical.

This procedure offers a method for measuring the rate of photosynthesis which depends directly on the rate of uptake of carbon dioxide by the photosynthetic organism. Hydrogencarbonate indicator changes colour with pH, which is determined by the concentration of carbon dioxide in solution.

The photosynthetic organism is a fast-growing green alga – such as Scenedesmus quadricauda – immobilised in alginate beads. These algal balls make it easy to standardise the amount of photosynthetic tissue in any investigation.

There is scope for students to develop the protocol to investigate a range of factors.

This protocol is adapted with permission from information on the Science and Plants for Schools (SAPS) website (see www.saps.org.uk ).

Lesson organisation

You can make up the algal balls in one lesson, discuss how to set up the main procedure, and carry it through in the next lesson. A preliminary investigation by teacher/ technician will allow you to estimate the amount of algal material and indicator to use to get a result with your equipment in the time available.

Apparatus and Chemicals

For each group of students:.

Transparent containers (glass bottles are ideal) with sealable lids, around 10 cm 3 , 6–12

Clamp stand, boss and clamp

Syringe barrel, 10 cm 3

Beaker, 100 cm 3 , 2

Cocktail stick to stir alginate

150 W lamp ( Note 5 )

Container of water as heat filter ( Note 6 )

Ruler/ tape measure

For the class – set up by technician/ teacher:

Colorimeter ( Note 1 )

Algal suspension, 2.5 cm 3 concentrated for each group ( Note 2 )

Sodium alginate, 2–3%, 100 cm 3 for a class of 30 students ( Note 3 )

Calcium chloride solution, 2%, 50 cm 3 per group

Hydrogencarbonate indicator, 50–100 cm 3 per group ( Note 4 )

Hydrogencarbonate indicator, standard colour scale, if colorimeter not available ( Note 4 )

Light meters, if available

Health & Safety and Technical notes

Do not look directly into the lamps. Do not touch the lamps while hot. Keep flammable material away from the lamps in use.

Read our standard health & safety guidance

1 Colorimeter. There is a linear relationship between absorbance of the indicator (at 550 nm – bright green filter) and pH over the range studied in this procedure.

2 Growing your alga. Prepare a culture of green alga such as unicellular Scenedesmus quadricauda . Make up a solution of algal enrichment medium, and subculture the alga into this. Aerate gently and keep at temperatures between 18–22 °C. Constant illumination ensures faster growth of the alga. After 3–4 weeks, the culture should have a green ‘pea soup’ colour. Subculture the alga again to maintain a healthy culture. You could use other algae, but Scenedesmus should produce 2 to 3 litres of dark green ‘soup’ in about 4 weeks from 50 cm 3 of original culture. (Details from SAPS Sheet 23).

3 Preparing solutions to make alginate beads (Refer to Recipe card 2):

• Dissolve 3 g of sodium alginate in 100 cm 3 of cold, pure water. Stir with a spatula every half hour or so. Leave overnight and stir in the morning.
• Dissolve 4 g of calcium chloride-6-water in 200 cm 3 of pure water in a 250 cm 3 beaker.

4 Hydrogencarbonate indicator. Refer to Recipe card 34 and Hazcard 32. Low hazard once made; must be made fresh by qualified staff using fume cupboard. The indicator is very sensitive to changes in pH, so rinse all apparatus with the indicator before use. Avoid exhaling over open containers of the indicator. Make up a ‘standard colour scale’ of reaction bottles containing buffers from pH 7.6- pH 9.2 with hydrogencarbonate indicator if students will not have access to a colorimeter.

5 Lamps. You need a brighter light than a standard 40 W or 60 W bench light. Low energy bulbs produce too limited a spectrum of light for full activity. 150 W tungsten or halogen lamps are best. 150 W portable halogen lamps have a stand and handle separate from the body of the lamp which makes them safer to handle. But they do produce heat, so you will need a heat filter for the investigation ( Note 6 ).

6 Heat filter. Use a large flat-sided glass vase (available from Ikea or Homebase or other domestic suppliers) or a medical ‘flat’ filled with water. With a high power lamp, the small volume in a medical ‘flat’ may get too hot for comfort.

7 Making alginate beads:

• When making up the alginate or diluting the algal culture it is essential to use pure water; otherwise calcium ions in the water will cause the alginate to 'set' prematurely.
• If your beads are not the size and texture you want, try different mixes with your active material, or different concentrations of sodium alginate (around 2–3%), or make the syringe nozzle narrower (with glass capillary tubing) or wider (by sawing off and adding a plastic tube). Different brands of alginate have different consistencies. You need a viscous mixture that will drip steadily through the syringe. Keep a note of what worked for this supply and keep your syringe barrels with nozzles for next time.

8 Neutral density filters: can be sourced as a film from photographic suppliers (for example, Lee filters www.leefilters.com . A neutral density filter reduces the amount of light transmitted by the same amount at all wavelengths.

Ethical issues

There are no ethical issues associated with this procedure.

SAFETY: Take precautions to avoid burns, fires and dazzle caused by hot, bright lamps. Do not leave the apparatus unattended overnight as the lamps are so hot.

Preparation of algal beads

a Concentrate your active algal culture ( Note 2 ). Do this by leaving 50 cm 3 to settle for 30 minutes in a measuring cylinder until you have a darker green sediment. Carefully pour off the pale green suspension to leave just 5 cm 3 of concentrated culture.

b Make up the solutions you need to prepare alginate beads ( Note 3 ).

c Mix 5 cm 3 of the algal culture with 5 cm 3 of the 3% sodium alginate solution ( Note 3 ) in a very small beaker.

d Clamp a syringe barrel above a beaker of calcium chloride solution (see diagram and Note 7 ) – making sure the tip of the syringe is well above the solution in the beaker.

e Pour the alga/alginate mixture through the syringe barrel so it drips through and forms beads in the beaker. Swirl the beaker gently as the drops fall. ( Note 7 .)

f Allow the beads to harden for a few minutes before straining them out of the beaker through a tea strainer.

g Rinse the beads in distilled water. The algae in the beads will stay alive for several months in a stoppered bottle of distilled water in the refrigerator.

Other materials

h Make up hydrogencarbonate indicator (see Note 4 and Recipe card 34). It is important to make up enough for the whole investigation as the depth of colour of this indicator is so variable. Make a few litres and keep for the duration of the investigations, aerating before each lesson. Make up a ‘standard colour scale’ of reaction bottles containing buffers from pH 7.6- pH 9.2 with hydrogencarbonate indicator if students will not have access to a colorimeter.

a Rinse 6 translucent bottles with hydrogencarbonate indicator solution.

b Add equal numbers of algal balls to each container – around 20.

c Add a standard volume of indicator to each container (7–10 cm 3 ).

d Replace the lid.

e Note the colour of the solution against a standard set of bottles of indicator, and/or measure the absorbance at 550nm using a colorimeter.

f Put one container in the dark. Set up the other containers at different light intensities – either by placing at different distances from the lamp, or by wrapping different neutral density filters ( Note 8 ) around the bottles.

g Place a heat filter between the light and the containers to absorb heat from the lamp. ( Note 6 .)

h After 30 minutes, note the colours of the solution at each distance.

i Once the bottles cover a range of colours, which will probably take more than 60 minutes, take samples from each bottle and measure the absorbance at 550 nm using a colorimeter. Start with the bottle that has changed most – the one at highest light intensity.

j Plot absorbance against light intensity.

k You could measure light intensity at each distance if a light meter is available, or calculate light intensity (1 ÷ distance 2 ).

Teaching notes

It takes at least an hour for colour changes to happen – so students will need to return to the lab at break or after lessons to ‘read’ the results.

Plotting absorbance against light intensity for the above procedure will show a proportional relationship at low light intensities, levelling off at higher intensities which indicates another limiting factor. The method with neutral density filters (rather than changing distance from the lamp) is reportedly more accessible for some students.

Carbon dioxide is unlikely to be the limiting factor here as the indicator contains a relatively high concentration of hydrogencarbonate ions.

Other factors to investigate include:

• amount of algal material: Shake 1 litre of algal culture, and leave 500 cm 3 , 250 cm 3 or 100 cm 3 to settle in measuring cylinders, saving the bottom 5 cm 3 each time. Make up into balls as above – each batch will have a different amount of algae, but the same surface area to volume ratio for the balls.
• surface area to volume ratio: Make smaller balls using a narrower bore to drip the alginate through.
• wavelength of light: Use coloured filters wrapped around the containers, or try different lamps (if you can identify the spectrum of light produced). Coloured filters will also alter the light intensity.

This practical reportedly works well for coursework investigations as students can suggest improvements or developments after some preliminary work with the technique.

Set aside a container of indicator and algal beads to keep in the lab for a few days. Students will be able to see changes to the colour of indicator according to the time of day – algae use up more carbon dioxide than they produce during the day and release carbon dioxide at night when they are not taking up any.

There is a linear response between absorbance of the indicator (at 550nm) and pH over the range studied in this procedure. Using a colorimeter (at 550nm) is one way to quantify this procedure. Alternatively you could set up a ‘standard colour scale’ with buffer solutions and indicator at the same concentration as the reagent in the investigation. Students can then compare their reaction vessels with the standards and interpolate to estimate pH.

You can also use this technique of immobilisation in an alginate bead to study enzymes or yeast cells. The beads can be packed into a column (for example, a syringe barrel) and a suitable substrate passed over the beads. Collect the products at the bottom of the column and use the immobilised enzymes or cells again and again without the need to separate them from the reactants.

Health and safety checked, September 2008

Related experiments

Investigating factors affecting the rate of photosynthesis

Investigating the light dependent reaction in photosynthesis

Adapted with permission from information on the Science and Plants for Schools (SAPS) website (see www.saps.org.uk ).

Alga Experiment Crazy Chemistry

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