Spiders under the influence

Field picture of an urban web. Dark paper is used to make the web more visible for data collection

The activities are as follows:

People use pharmaceutical drugs, personal care products, and other chemicals on a daily basis. For example, we take medicine when we are sick to feel better, and use perfumes and cologne to make ourselves smell good. After we use these chemicals, where do they go? Often, they get washed down our drains and end up in local waterways. Even our trash can contain these harmful chemicals. For example, when coffee grounds are thrown into the trash, caffeine gets washed into our waterways.

Animals in waterways, like insects, live with these chemicals every day. Many insects are born and grow in the water, absorbing the drugs over their lifetime. As predators eat the insects, the chemicals are passed on, working their way through the food web. For example, spiders living along riverbanks feed off aquatic insects and absorb the drugs from their prey.

Just as chemicals change human behavior, they change spider behavior as well! Effects of drugs on spiders have been studied since the 1940s. Dr. Peter Witt first discovered that chemicals change spider web construction. Peter gave caffeine, and a few other drugs, to spiders to see if they would build their webs during the day instead of at night, which is when they usually work. After giving his test spiders some of the drugs, the spiders still created their webs at night. However, he noticed something unexpected – the web structure of spiders on drugs was completely different from normal webs. The webs were different sizes and had more spacing between each thread. Normal webs help spiders to easily catch prey. Irregularly shaped webs were not good at catching prey because insects could fly right through the large spaces. After his study, Peter knew that drugs were bad for spiders.

Chris (they/them), a current resident of Baltimore and a spider enthusiast, lives in a watershed that is affected by chemical pollution. They wanted to build on Peter’s research by looking at spider webs in the wild instead of in the lab. Chris knew that many types of spiders live near streams and are exposed to toxins through the prey they eat. Chris wanted to compare the effects of the chemicals on spiders in rural and urban environments. By comparing spider webs in these two habitats, they could see how changed the webs are and infer how many chemicals are in the waterways.

Chris worked with Aaron, a local high school teacher, to do this research. They collected images of spiderwebs in areas around Baltimore. They chose two sites: Baisman Run, a rural site far from the city, and Gwynns Run, an urban site close to the city. Chris traveled to the sites and took pictures of eight spiderwebs at each location. Chris and Aaron expected that urban streams would have higher concentrations of chemicals than rural areas because more people live in cities.

When they got back to the lab, Aaron took the pictures and used a computer program to count the number of cells and calculate the total area of each web. These data offer a glimpse into whether spiders near Baltimore are exposed to harmful pharmaceutical chemicals and personal care products. If spiders are exposed to these chemicals, the webs will have fewer, but larger cells than a normal web. The cells will also have irregular shapes.

Featured scientists: Chris Hawn from University of Maryland Baltimore County and Aaron Curry from Baltimore Ecosystem Study LTER

Flesch–Kincaid Reading Grade Level = 7.8

Additional teacher resources related to this Data Nugget include:

  • You can watch Aaron describe his Research Experience for Teachers project here.


Breathing in, Part 1

Susan stands in a reforestation experiment near the Chesapeake Bay.

The activities are as follows:

Photosynthesis is the process by which trees and other plants trap the sun’s energy within the molecular bonds of glucose (C6H12O6), a type of sugar. During photosynthesis, oxygen (O2) is released as a byproduct. For this reason, trees are often portrayed as the lungs of the planet “breathing out” oxygen.

Oxygen is then used by living things for cellular respiration. Your cells use oxygen to free the energy stored within glucose. That is why you, and most living things, need oxygen to survive.

But there’s another aspect of photosynthesis that’s just as important as the release of oxygen. Look at a tree or other plant out your window – how did it get so big? The answer is in the equation for photosynthesis. Carbon dioxide (CO2) and water (H2O) provide the carbon, hydrogen, and oxygen needed to build glucose. Trees use glucose as both an energy source and construction material. As they grow, they arrange glucose in long, winding structures. Some of this carbon becomes part of the plant for as long as they live. This means that the carbon that builds plants comes from the air! This process of pulling carbon out of the atmosphere and holding on to it for long periods of time is known as carbon sequestration or carbon accumulation. It’s what the trees do when they use photosynthesis to “breathe in.”

These processes caught Kristina’s interest. She wanted to know more about how carbon accumulation differed across the globe. So, in 2006, she and a small team of scientists created a database using information from 91 studies on carbon in trees.

In the meantime, Susan was working at the Nature Conservancy and getting tons of questions from people who wanted to plant new forests to help fight climate change. People wanted to know what kinds of forests to plant, and how much carbon they might be able to accumulate. Susan, like Kristina, knew that carbon accumulation differed across the globe and wanted to give people the right numbers for the right places. She started gathering carbon data by sifting through thousands of scientific papers. In the process, she found Kristina’s work. One day, Susan called Kristina to chat.

Kristina and Susan decided they needed to work together to learn more about how carbon accumulation rates differ across various types of forests found around the world. So, they set out to build on previous research and get more accurate measurements. Instead of doing their own new study, they needed to gather data from thousands of existing studies in locations from all over the earth. So that’s exactly what they did. Kristina and Susan, along with an international team of researchers, began their work creating ForC, the Global Forest Carbon Database.

ForC is an open-access database containing over 40,000 records from more than 10,000 plots in over 1,500 geographic areas. All of the data come from published research by scientists and include studies from every forested climate zone. It is a living database that is always being updated as scientists publish their work, making it the most complete source of forest carbon data in the world! It was exactly what Kristina and Susan needed.

Kristina and Susan used ForC to investigate global carbon capture by young regrowing forests. Based on their previous research, they thought that, since tropical forests regrow fastest due to a year-round warm and wet climate, they would have the highest rate of carbon accumulation. In order to study carbon accumulation, they selected 13,112 measurements from young, regrowing (<30 years old) forests around the world. They grouped measurements by forest type, averaged them, and compared their data. With these values, they could inform policy decisions and prioritize forest regrowth in parts of the world that would have the highest impact. Review the table below for information on the six main forest types that Kristina and Susan studied.

Featured scientists: Kristina J. Anderson-Teixeira, Smithsonian Conservation Biology Institute & Susan C. Cook-Patton, The Nature Conservancy. Written by Ryan Helcoski.

Flesch–Kincaid Reading Grade Level = 9.1

Additional classroom resources for this Data Nugget:

  • Here is a scientific article related to this activity: Anderson KJ, Allen AP, Gillooly JF, Brown JH. (2006). Temperature-dependence of biomass accumulation rates during secondary succession. Ecology Letters Jun: 9(6):673-82.
  • If you would like to explore the ForC database in your classroom, students can view the shiny app. Anyone that feels even more ambitious can see the raw data.

To reflect, or not to reflect, that is the question

Jen stops to take a photo while conducting fieldwork in the Arctic.

The activities are as follows:

Since 1978, satellites have measured changes in Arctic sea ice extent, or the area by the North Pole covered by ice. Observations show that Arctic sea ice extent change throughout the year. Arctic sea ice reaches its smallest size at the end of summer in September. Scientists who look at these data over time have noticed the sea ice extent in September has been getting smaller and smaller since 1978. This shocking trend means that the Arctic sea ice is declining, and fast! 

Why does this matter? Well, it turns out that Arctic sea ice plays a major role in the world’s climate system. When energy from the Sun reaches Earth, part of the energy is absorbed by the surface, while the rest is reflected back into space. The energy that is absorbed becomes heat, and warms the planet. The amount of energy reflected back is called albedo.

The higher the albedo, the more energy is reflected off a surface. Complete reflection is assigned a value of 1 (100%) and complete absorption is 0 (0%). Lighter colored surfaces (e.g., white) have a higher albedo than darker colored surfaces (e.g., black). Sea ice is white and reflects about 60% of solar energy striking its surface, so its albedo measurement is 0.60. This means that 40% of the Sun’s energy that reaches the sea ice is absorbed. In contrast, the ocean is much darker and reflects only about 6% of the Sun’s energy striking its surface, so its albedo measurement 0.06. This means that 94% of the Sun’s energy that reaches the ocean is absorbed.

Jen (second from left) preparing to teach her students at the University of Colorado Boulder while working in the Arctic. Photo by Polar Bears International.

Jen first became interested in sea ice in the summer of 2007, when a record low level of sea ice caught scientists off guard. They worried that if the albedo of the Arctic declines, energy that used to be reflected by the white ice will be absorbed by the dark oceans and lead to increased warming. At the time, Jen was working with new satellite observations and found it fascinating to understand what led to the record low sea ice year. To continue her passion, Jen joined a team of scientists studying the Arctic’s energy budget. 

Jen and her team predicted that the decline in the light-colored sea ice will cause Arctic albedo to decrease as well. Jen used incoming and reflected solar energy data to determine the changes in the Arctic’s albedo. These data were collected from satellites as part of the Clouds and Earth’s Radiant Energy System (CERES) project. Then, Jen compared the albedo data to changes in the extent of sea ice from satellite images to look for a pattern. 

Featured scientist: Jen Kay from the Cooperative Institute for Research in Environmental Sciences and the Department of Atmospheric and Oceanic Sciences at the University of Colorado Boulder. Written by Jon Griffith with support from AGS 1554659 and OPP 1839104.

Flesch–Kincaid Reading Grade Level = 9.6

Fertilizer and fire change microbes in prairie soil

Christine collecting samples from the experimental plots to measure root growth.
Christine collecting samples from the experimental plots to measure root growth.

The activities are as follows:

Stepping out into a prairie feels like looking at a sea of grass, with the horizon evoking a sense of eternity. Grasses and other prairie plants provide important benefits, such as creating habitat for many unique plants, mammals, insects, and microbes. They also help keep our water clean by using nutrients from the soil to grow. When plants take up these nutrients, they prevent them from going into streams. High levels of plant growth also keeps carbon bound up in the bodies of plants instead of in the atmosphere.  

Prairies grow where three environmental conditions come together – a variable climate, frequent fires, and large herbivores roaming the landscape. However, prairies are experiencing many changes. For example, people now work to prevent fires, which allows forest species to establish and eventually take over the prairie. In addition, a lot of land previously covered in prairie is now being used for agriculture. When land is used for agriculture, farmers add nutrients through fertilizer. With all these changes, prairie ecosystems have been declining globally. Scientists are concerned that as they disappear so will the benefits they provide. 

Lydia and Christine are two scientists contributing to the effort to learn more about how to preserve prairies. They both became interested in studying soil because of their appreciation for prairies at a young age. For Lydia, she lived in an area that was covered by trees and farmland, but knew at one time it used to be prairie. This made her want to learn more about prairie environments and how places like where she grew up have changed through history. For Christine, she grew up surrounded by prairies where she developed a passion and curiosity for the natural world. Especially for the organisms living in the soil that you cannot see, called microbes. 

These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.
These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.

Lydia and Christine read about how grassland scientists have been doing research to learn more about what happens when fire is stopped and excess nutrients are added. These changes reduce biodiversity and affect which species of plants can grow in the prairie. However, Lydia and Christine noticed that the research had been mostly focused on what happens aboveground.  Lydia and Christine had a hunch that the aboveground communities were not the only things changing. They thought that belowground components would be changed by fire and fertilizer too. They turned their focus to microbes in the soil, because they also use nutrients. In addition, they thought these microorganism would be affected by the changes in aboveground plant biodiversity. 

To see if this was true, they used data that they and other scientists collected at Konza Prairie Biological Station from a large field experiment. The experiment was set up in 1986 and the treatments were applied at the field site every year until 2017! Lydia and Christine focused on the fertilizer (nitrogen) addition and prescribed burning treatments to answer their questions. The nitrogen treatment had eight plots where nitrogen had been added and eight with no nitrogen as a control. Similarly, the prescribed burn treatment was applied to eight plots, while eight plots had no burning as a control. These two treatments were also crossed with each other, meaning that some plots were burned and nitrogen was added.

Lydia and Christine expected the types of microbes in the soil to change in response to the nitrogen and burning treatments because of the different aboveground plant communities and difference in soil nutrients. Soil microbial communities can change in multiple ways. First, the number of unique species can increase or decrease, measured as richness. The other way is how many individuals of each species there are in the community, measured as evenness. Taken together, richness and evenness give a measure of diversity, which can be summarized using the Shannon-Wiener index. The value will get bigger if either richness or evenness increases because it incorporates both. For example, a community with five species that has equal abundance of each will have a larger Shannon-Wiener index than a community with five species where one species has a lot more individuals than the other four.  

Featured Scientists: Lydia Zeglin and Christine Carson from the Konza Prairie Biological Station. Written By: Jaide Allenbrand

Flesch–Kincaid Reading Grade Level = 10.4

Mangroves on the move

mangrove in marsh
A black mangrove growing in the saltmarshes of northern Florida.

The activities are as follows:

All plants need nutrients to grow. Sometimes one nutrient is less abundant than others in a particular environment. This is called a limiting nutrient. If the limiting nutrient is given to the plant, the plant will grow in response. For example, if there is plenty of phosphorus, but very little nitrogen, then adding more phosphorus won’t help plants grow, but adding more nitrogen will. 

Saltmarshes are a common habitat along marine coastlines in North America. Saltmarsh plants get nutrients from both the soil and the seawater that comes in with the tides. In these areas, fertilizers from farms and lawns often end up in the water, adding lots of nutrients that become available to coastal plants. These fertilizers may contain the limiting nutrients that plants need, helping them grow faster and more densely.

One day while Candy, a scientist, was out in a saltmarsh in northern Florida, she noticed something that shouldn’t be there. There was a plant out of place. Normally, saltmarshes in that area are full of grasses and other small plants—there are no trees or woody shrubs. But the plant that Candy noticed was a mangrove. Mangroves are woody plants that can live in saltwater, but are usually only found in tropical places that are very warm. Candy thought the closest mangrove was miles away in the warmer southern parts of Florida. What was this little shrub doing so far from home? The more that Candy and her colleague Emily looked, the more mangroves they found in places they had not been before.

Candy and Emily wondered why mangroves were starting to pop up in northern Florida. Previous research has shown nitrogen and phosphorus are often the limiting nutrients in saltmarshes. They thought that fertilizers being washed into the ocean have made nitrogen or phosphorus available for mangroves, allowing them to grow in that area for the first time. So, Candy and Emily designed an experiment to figure out which nutrient was limiting for saltmarsh plants. 

mangrove saltmarsh researchers
Candy (right) and Emily (left) measure the height of a black mangrove growing in the saltmarsh.

For their study, Candy and Emily chose to focus on black mangroves and saltwort plants. These two species are often found growing together, and mangroves have to compete with saltwort. Candy and Emily found a saltmarsh near St. Augustine, Florida, in which they could set up an experiment. They set up 12 plots that contained both black mangrove and saltwort. Each plot had one mangrove plant and multiple smaller saltwort plants. That way, when they added nutrients to the plots they could compare the responses of mangroves with the responses of saltwort. 

To each of the 12 plots they applied one of three conditions: control (no extra nutrients), nitrogen added, and phosphorus added. They dug two holes in each plot and added the nutrients using fertilizers, which slowly released into the nearby soil. In the case of control plots, they dug the holes but put the soil back without adding fertilizer.

Candy and Emily repeated this process every winter for four years. At the end of four years, they measured plant height and percent cover for the two species. Percent (%) cover is a way of measuring how densely a plant grows, and is the percentage of a given area that a plant takes up when viewed from above. Candy and Emily measured percent cover in 1×1 meter plots. The cover for each species could vary from 0 to 100%.

Featured scientists: Candy Feller from the Smithsonian Environmental Research Center and Emily Dangremond from Roosevelt University

Flesch–Kincaid Reading Grade Level = 8.3

Corals in a strange place

Marine Biologist, Karina, snorkeling in the mangroves. Photo by John Finnerty.

The activities are as follows:

When you imagine a coral, you likely picture it living on a coral reef, bathed in sunlight, surrounded by crystal clear waters teeming with colorful fishes. But corals can actually live in a range of habitats, even habitats that are sometimes murky and much darker!

As marine biologists, Karina and John often snorkel around the mangroves in Belize, where they do their research. Mangroves are trees that have roots able to grow in saltwater. By capturing mud and sediment, these underwater roots build habitat for marine life. While Karina and John were documenting the different marine life that can grow on underwater roots, they noticed something shocking. The same corals that live on coral reefs were growing in the mangrove forests too! This surprised Karina and John because coral reefs and mangrove forests are very different habitats. Coral reefs have clear water and bright light, while mangrove forests are darker with murky water that has a lot of nutrients. How can corals live in such different places?

Karina and John started to wonder if the corals that live in the mangroves look different than the corals on the reefs. Sometimes animals can look different based on where they live. These differences may be adaptations that help them live in different environments. Karina and John measured differences between two different coral species that were found in both habitat types. The two species they used are the mounding mustard hill coral and the branching thin finger coral.   

Featured scientists: Karina Scavo Lord and John Finnerty from Boston University

Flesch–Kincaid Reading Grade Level = 8.9

Data Nuggets researchers lead collaborative study examining representation in STEM curriculum

Melissa and Liz presenting Data Nuggets.
Melissa (left) and Liz (right) presenting Data Nuggets at the LTER All Scientists Meeting.

When you were a child, what was your image of a scientist? Could you imagine yourself in those shoes?

A new, National Science Foundation-funded study led by Michigan State University researchers and others aims to better understand how science instruction that contains diverse scientist role models affects student attitudes about science, technology, engineering and mathematics—STEM—courses and careers. 

Data Nuggets, a project that has created free STEM classroom activities since 2011, is integral to the new study. Data Nuggets was founded by postdoctoral researchers Elizabeth Schultheis and Melissa Kjelvik, both of whom conducted doctoral research at the W.K. Kellogg Biological Station. The Data Nuggets activities were co-developed through collaborations between scientists and K-16 educators.

MSU ecologist Marjorie Weber will lead the study. Other members of the research team include Schultheis and Kjelvik, and Cissy Ballen and Ash Zemenick of Auburn University.

Post originally from Kellogg Biological Station. You can also read about the study here.

Limit by limit: Nutrients control algal growth in Arctic streams

The Arctic Stream Team. Frances, Breck, Abby, Alex, Jay, and Arial at Toolik Field Station in 2019. 

The activities are as follows:

You rely on the nutrients from the foods you eat to grow and thrive. Other organisms, like microbes, do as well! Aquatic algae, a type of microbe that live in the water, need to take in nutrients from their surroundings for growth. Two important nutrients for algal growth are nitrogen (N) and phosphorous (P).

Sometimes the environment does not have all the nutrients that aquatic algae need to grow. When one nutrient is less available compared to others, algae can become nutrient limited. Research on nutrient limitation started with Justus Liebig, a 19th century scientist who proposed the “law of the minimum.” The law states that the nutrient available in the lowest amount relative to demand will limit overall growth and production. This means that growth is not controlled by all the nutrients, but by the scarcest one (the “limiting factor”). When more than one nutrient limits growth, algae are considered co-limited. This just means that a combination of two nutrients are needed for algae to grow. Knowing what nutrients are limiting growth helps scientists understand how an ecosystem is working.  

From other research we know that many ecosystems, including those in the Alaskan Arctic, are phosphorus-limited. Scientists figured this out because they found if they added phosphorus, then algae growth increased. However, climate change could change this. As the Arctic warms, ecosystems on land might start to release nutrients in higher amounts or new proportions into the water. These extra nutrients will likely cause increases in algae growth in streams and ponds, which in turn could change food webs and nutrient cycling. It is therefore important to understand which nutrients are currently limiting algae growth before climate change changes things even more. This starts with tests to see how Arctic algae grow in response to changes in N, P, and N and P in the water.  

A team of scientists got to work on this question! Arial, Jay, Frances, Alex, Breck, and Abby are all interested in understanding how climate change may alter nutrient limitations in Arctic streams. Each team member has a unique role in the larger research project. For example, undergraduate researcher Abby spent her 2019 summer at Toolik Field Station in Northern Alaska as part of a research opportunity. She explored nutrient limitation in one particular lake, called Lake I8. 

Abby used small cups that placed into the streams that fed into Lake I8. These cups were filled with agar gel, a material used in labs to grow microbes. Each cup contained different nutrient treatments. Abby used four different treatments in her cups: (1) a control (agar only), (2) agar + nitrogen, (3) agar + phosphorus, and (4) agar + nitrogen + phosphorus. On the top of each cup, she placed a glass disk to provide a surface for the algae to grow.

A. Cups before going into the stream. B. Abby putting out her cup treatments into an Arctic stream. C. Cups incubating under water in an Arctic stream. D. Analyzing Chlorophyll a extracted from the cups. 

Abby put 5 replicate cups for each treatment at both the Inlet and Outlet streams on the I8 Lake. She left them underwater for 4 weeks. She brought the cups back to the lab to measure the algae that grew on each glass disk. Abby measured how much algae grew on each disk by measuring the amount of Chlorophyll a, the green pigment that helps plants photosynthesize. The more pigment, the more the algae is growing. Abby compared the data from the control to each of the other treatments. When there is more growth in a treatment compared to the control, that means a particular nutrient was limiting at that location. Abby expected that the streams would be limited by the amount of phosphorus, but not the amount of nitrogen. She predicted algae would grow more when they are given additional phosphorus compared to the control treatment.

Featured scientists: Abigail Rec from Gettysburg College; Frances Iannucci, Alex Medvedeff, and Breck Bowden from University of Vermont; Arial Shogren and Jay Zarnetske from Michigan State University

Flesch–Kincaid Reading Grade Level = 8.6

Are plants more toxic in the tropics?

Carina looking for jaboncillo plants in Costa Rica.

The activities are as follows:

Éste Data Nugget también está disponible en Español:

Long before chemists learned how to make medicines in the laboratory, and even long before there were chemists, people found their medicines in plants. To this day, people still extract some medicinal drugs from plants, while others that we used to get from plants are now manufactured in factories.

Why do plants make these chemicals that are often so useful to people? One reason is that plants can’t run away or hide from herbivores, the animals that eat them. So instead, many plants defend themselves using chemicals that are poisonous or toxic to herbivores. As pharmacists say, “the dose makes the poison,” meaning it all comes down to quantity. A tiny amount of caffeine helps you stay awake, but you wouldn’t feel so great if you ate a giant salad of coffee leaves. Similarly, an herbivore that tries to eat coffee leaves would get sick, so it will avoid eating coffee leaves. That’s why plants have evolved to make chemicals – because the chemicals discourage animals from eating the plants. This benefit helps plants survive and reproduce, and any benefit to humans is an unintentional side effect of evolution.

Carina is fascinated by the amazing ways that plants have evolved to avoid being eaten. She also loves researching tropical forests near the Equator. Tropical forests have many more kinds of plants and insects than temperate places, which are farther from the Equator. One important difference between the climates is that the tropics don’t have harsh winters that kill insects. Therefore, biologists think that tropical plants get eaten more by herbivores.

Some plants have high chemical diversity, and make many kinds of chemicals. Biologists have observed that some plants with high chemical diversity are especially difficult for herbivores to eat. Carina thought that maybe stronger insect attacks in the tropics would lead the tropical plants to evolve higher chemical diversity than temperate plants in order to better protect them from herbivory. She thought that over time, the individual plants that had more types of chemicals in their leaves would grow and reproduce more. This would allow them to pass on their traits to the next generation.

Jaboncillo plants with herbivore damage in Costa Rica.

To answer her question, Carina collected seeds from wild pokeweed plants in Michigan and Florida. She also collected seeds in Costa Rica from jaboncillo, a species closely related to pokeweed that lives in tropical countries in Latin America. She chose these locations because they vary in how close they are to the equator, and how severe their winters can be. Michigan has long and very cold winters (a temperate climate), Florida has mild winters with occasional freezing (a subtropical climate), and in Costa Rica temperatures never go below freezing (a tropical climate).

She started by growing 15-20 plants from each location in a greenhouse. Then, she extracted chemicals from their leaves and analyzed the chemical diversity of each plant. Chemical diversity is measured by an index that includes how many and how abundant different kinds of chemicals are. Carina predicted that the tropical plants would have the highest chemical diversity. She also predicted that the subtropical plants would have higher chemical diversity than the temperate plants.

Featured scientist: Carina Baskett, Michigan State University

Flesch–Kincaid Reading Grade Level = 10.8

Working to reduce the plastics problem

stretching the raw, preformed polymers
Nick (right) and one of his students (left) stretching the raw, preformed polymers.

The activities are as follows:

Plastics are materials that can be shaped easily and are used for many functions. This has made them extremely popular across the world. Thousands of products are made using plastic, including parts of cell phones, food wrappers from your lunch, and even the stitches you may need after an injury. In fact, if you look around right now, you can probably spot at least ten items made of plastic!

Once a plastic is made, it tends to stick around. Synthetic plastics, made by humans from petroleum, cannot be broken down by nature’s decomposers – bacteria and fungi. This means they impact the environment for many, many years. Some types can take thousands of years or longer to break down! 

Nick is a chemist concerned with the negative impacts caused by plastics. He knows that in order to reduce the amount of synthetic plastics in the environment, we need an alternative. And, this alternative needs to be just as good as the synthetic plastic it is replacing. Nick and his undergraduate students at Northland College are testing new ways to make plastics that are biodegradable, meaning they can be decomposed naturally and won’t last as long in the environment. His research focuses on stretchy plastics, called elastomers.Elastomers are what make up rubber bands, tires, hoses, non-latex gloves, and many more items we use every day. 

To try to solve the problem of making a biodegradable elastomer that has all the qualities of a synthetic one, Nick and his students got to work. First, they had to consider the chemical structure of plastics. Plastics are made of polymers. “Poly” means “many” and “mer” means “parts”. This means that plastics are made of long chain molecules with many repeating parts. These repeating parts are called monomers. Different monomers can be used to make different types of plastic.

Nick chose to test two biodegradable monomers – diglycerol and meso-erythritol. Diglycerol is cheap and easy to buy. However, it might be too soft when used on its own. Meso-erythritol is more expensive, but more rigid. They wanted to use diglycerol and meso-erythritol because the chemical structures have the potential to create something that is not too rigid and not too flexible.

Nick and his students designed an experiment in which they tested elastomers made from each of the monomers (diglycerol and meso-erythritol) alone, as well as elastomers made using both types of monomers. They made elastomers with the following percentage ratios of diglycerol over meso-erythritol: 100/0, 75/25, 50/50, 25/75, 0/100. The team was hoping to find the “sweet spot” between a product that is too stiff, and one that is not stiff enough to be useful in elastic materials. Once they finished making their elastomers, they prepared the stretch tests. 

To start a stretch test, the team had to stamp out a piece of material from each elastomer, creating samples with the same size, shape, and thickness. They also cut pieces from rubber bands made of synthetic plastics to compare as a control. Next, they tested the elastomers using a machine that measures how much force is applied (stress) as a material is stretched (strain), both important measures of elasticity. The stress, or force per unit of area, is measured in megapascals (MPa) while the strain, or amount of stretch, is measured as a percent of the original length. 

Featured scientist: Nick Robertson from Northland College. Written by: Theresa Paulsen from Ashland High School, Wisconsin

Flesch–Kincaid Reading Grade Level = 9.6

For additional information on the plastic problem, and Nick’s research, check out the following resources: