5.14.25

PFAS: Our forever problem

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Gary during his research experience with Natalia.

The activities are as follows:

Per- and polyfluoroalkyl substances (PFAS) are a group of pollutants that are found in many commonly used products. They are in clothing, non-stick pans, and even the linings of cans and other food containers. Because PFAS are used in so many everyday products, they make their way into the environment. Once these compounds are in our environment, they will be there for up to a thousand years! For this reason, PFAS are known as “forever chemicals.”

Water is a very common place to find these forever chemicals. Normal water treatment processes do not remove PFAS from our drinking water. Consequently, PFAS are found in the blood of humans and animals worldwide. In humans, they have been shown to cause liver damage, cancer, harm immune systems, and other health issues.

Natalia is a researcher at Florida International University who studies PFAS and other chemicals in the environment. She wanted to make sure she shared her work with the public, as this topic is so important for us all. She thought one way to do this would be to work with local teachers.

Gary, a science teacher at a school nearby, joined Natalia’s lab for the summer. When the opportunity became available, Gary jumped at the chance to investigate and learn more about Florida’s amazing environment and work in the field with scientists. He was so excited because Natalia had appeared on TV and radio shows and had authored articles in leading science magazines. When they met, Natalia described PFAS to Gary, and he was immediately captivated.

Gary and Natalia decided to work together to explore PFAS in Biscayne Bay. This area is a crucial estuary around Miami, providing a unique environment that supports diverse wildlife and local industries. As a young person, Gary would go shrimping along the bay. He really enjoyed the natural beauty of such a precious resource right in his backyard. Unfortunately, today, Biscayne Bay faces numerous
environmental challenges.

Map showing Gary’s research sites where he sampled PFAS

One challenge is PFAS, which enters the estuary through water pollution that drains into the bay. Gary expected PFAS to be highest in the urban freshwater streams that drain into the bay because human activity is high, and a lot of chemicals are released into the water. He thought that the bay would also have high concentrations of PFAS because the streams drain into the bay, but the surrounding land limits the water from mixing with the ocean. Once the water makes it to the ocean, the chemicals should be able to mix with the larger body of water, lowering the concentration of PFAS.

Gary and Natalia identified 16 water sampling sites in water bodies near Miami. They broke these sites into three categories: (1) freshwater rivers that bring water from urban areas into the bay, (2) brackish water, which means a mixture of freshwater and saltwater, located within Biscayne Bay, and (3) salt water found in the Atlantic Ocean. Courtney, a graduate student in Natalia’s lab, joined the team to assist Gary with collecting data and using the technical instruments needed to analyze the samples. Together, they collected one 500 mL sample from each site. To ensure accuracy in the collection of data, they collected two samples from the South Beach pump station site. Gary and Natalia brought the samples back to the lab and ran the samples through instruments that measured PFAS levels. Gary predicted that he would find high levels of PFAS in the freshwater canals and the brackish water of Biscayne Bay, but less in the open ocean.

Featured scientists: Gary Yoham from Miami Senior High School with Natalia Soares Quinete and Courtney Heath from Florida International University

Flesch–Kincaid Reading Grade Level = 7.3

8.1.24

Poop, poop, goose!

Cackling Goose next to a pile of goose poop, or feces
Cackling Goose next to a pile of goose poop, or feces. Photo by Andrea Pokrzywinski.

The activities are as follows:

Each spring, millions of birds return to the Yukon-Kuskokwim Delta. This delta is where two of the largest rivers in Alaska empty into the Bering Sea. It is also one of the world’s most significant habitats for geese to breed and raise their young. 

With all these geese coming together in one area, they create quite a mess – they drop tons of poop onto the soil. So much poop in fact, that scientists wonder whether poop from this area in Alaska could have a global impact! Climate change is a worldwide environmental issue that is caused by too many greenhouse gasses being released into our atmosphere. Typically, we think of humans as the cause of this greenhouse gas release, but other animals can contribute as well. 

When poop falls onto the soil it is decomposed by bacteria. Bacteria release methane (CH4), a potent greenhouse gas. The more geese there are, the more poop they will produce and the more food there will be for soil bacteria. By increasing the amount of greenhouse gasses that are released by soil bacteria, geese might actually indirectly contribute to global climate change.

Trisha is an ecosystem ecologist who scoops goose poop for research projects. Her research is looking into whether animals, other than humans, can change the carbon cycle. Trisha teamed up with Bonnie, a fellow ecosystem ecologist. Bonnie studies how matter moves between the living parts of the environment, such as plants and animals, and the nonliving parts. She is especially interested in how bacteria in the soil play a role in the carbon cycle.

Together, the team designed a three-year project to figure out the effects of goose poop on the carbon cycle. Each summer, a large team of researchers spend 90 days camping on remote sites near the Yukon-Kuskokwim Delta. The team scooped up poop from nearby goose habitats to use in their experiments. They set up six control plots where they added no poop and six treatment plots where they added poop. From these twelve plots, the team measured methane emissions from the soil. Methane was measured as methane flux in micromoles, or µM. These data helped them determine how ecosystems respond to geese by measuring whether goose poop affects methane production by soil bacteria.  

Featured scientists: Trisha Atwood of Utah State University and Bonnie Waring of Imperial College. Written by Andrea Pokrzywinski.

Flesch–Kincaid Reading Grade Level = 8.7

Additional teacher resources related to this Data Nugget include:

6.7.24

Seagrass survival in a super salty lagoon

A researcher in the Dunton Lab measures seagrasses underwater using a mask, snorkel, and a white PVC quadrat.

The activities are as follows:

Seagrasses are a group of plants that can live completely submerged underwater. They grow in the salty waters along coastal areas. Seagrasses are important because they provide a lot of benefits for other species. Like land plants, seagrasses use sunlight and carbon dioxide to grow and produce oxygen in a process called photosynthesis. The oxygen is then used by other organisms, such as animals, for respiration. Other organisms use seagrasses for food and habitat. Seagrass roots hold sediments in place, creating a more stable ocean bottom. In addition, the presence of seagrasses in coastal areas slows down waves and absorbs some of the energy, protecting shorelines.

Unfortunately, seagrasses are disappearing worldwide. Some reasons include damage from boats, disease, environmental changes, and storms. Seagrasses are sensitive to changes in their environment because they have particular conditions that they prefer. Temperature and light levels control how fast the plants can grow while salinity levels can limit their growth. Therefore, it is important to understand how these conditions are changing so that we can predict how seagrass communities might change as well.

Ken is a plant ecologist who has been monitoring seagrasses in southern Texas for over 30 years! Because of his long-term monitoring of the seagrasses in this area, Ken noticed that some seagrass species seemed to be in decline. Kyle started working with Ken during graduate school and wanted to understand more about what environmental conditions might have caused these changes. 

Manatee grass (Syringodium filiforme) located within the Upper Laguna Madre.

Texas has more seagrasses than almost any other state, and most of these plants are found in a place called Laguna Madre. During his yearly seagrass monitoring, Ken noticed that from 2012 – 2014 one of the common seagrasses, called manatee grass, died at many locations across Laguna Madre. Since then, the seagrass has grown back in some places, but not others. Kyle thought this would be an opportunity to look back at the long-term dataset that Ken has been collecting to see if there are any trends in environmental conditions in years with seagrass declines.

Each year, Ken, Kyle, and other scientists follow the same research protocols to collect data to monitor Laguna Madre meadows. Seagrass sampling takes place 2 – 4 times a year, even in winter! To find the manatee grass density, scientists dig out a 78.5 cm2 circular section (10 cm diameter) of the seagrass bed while snorkeling. They then bring samples back to the lab and count the number of seagrasses. While they are in the field, they also measure environmental conditions, like water temperature and salinity. A sensor is left in the meadow that continuously measures the amount of light that reaches the depth of the seagrass.

Kyle used data from this long-term monitoring to investigate his question about how environmental conditions may have impacted manatee grass. For each variable, he calculated the average across the sampling dates to obtain one value for that year. He wanted to compare manatee grass density with salinity, water temperature, and light levels that reach manatee grass. He thought there could be trends in environmental conditions in the years that manatee grass had low or high densities.

Featured scientists: Kyle Capistrant-Fossa (he/him) & Ken Dunton (he/him) from the U-Texas at Austin

Flesch–Kincaid Reading Grade Level 9.8

Additional teacher resources related to this Data Nugget:

There is another Data Nugget that looks at these seagrass meadows! Follow Megan and Kevin as they look at how photosynthesis can be monitored through the sound of bubbles and the acoustic data they produce.

Follow this link for more information on the Texas Seagrass Monitoring Program, including additional datasets to examine with students.

There are articles in peer-reviewed scientific journals related to this research, including:

National Park Service information about the Gulf Coast Inventory and Monitoring.

Texas Parks and Wildlife information on seagrass:

8.15.23

Lake Superior Rhythms

A sandy Lake Superior shoreline near Bayfield, WI.

The activities are as follows:

Gena and Ali are sisters who grew up in Bayfield, Wisconsin on the south shore of Lake Superior. When they were young, they spent many summer days sailing in the Apostle Islands National Lakeshore with their parents and friends. As they relaxed on the beach, they would watch how the lake changed. Even over a short period of time, they would see the landscape change. In just a few hours, a rock that was visible above the water’s surface when they arrived would slowly become submerged, only to reappear several hours later.

In high school, Gena and Ali set out to learn about the geophysical forces acting on Lake Superior. They wanted to investigate why they would sometimes see such dramatic fluctuations in water levels. They also wanted to know why water from rivers and streams would sometimes flow out into the lake, while other times it would flow back into the tributaries.

Ali presents research results on how the seiche changes the local water levels.

They learned that large lakes exhibit a phenomenon called a seiche (pronounced saysh). Like tides, a seiche is a periodic rising and falling of water levels. However, tides and seiches are caused by two different forces. Whereas tides are connected to the sun and moon, seiches are caused by changes in atmospheric pressure and strong winds.

Many atmospheric events can exert force on the water, including storms that come and go, heavy rain, cold fronts blowing through, or the calming of strong winds. You can think of Lake Superior as a giant bathtub, and the seiche is the water sloshing back and forth as it is pushed by a force and then released.

Gena and Ali realized that the seiche probably explained the water level changes they saw on Lake Superior. They became curious to learn more about the lake’s seiche pattern. An atmospheric event can cause the water to slosh from one side of the lake to the other several times. They predicted the seiche would look like a wave pattern as the water comes and goes.

The sensor with data recorder on the dock inside a boathouse.

To test their ideas, they decided to investigate how often the water switched directions and how much the water level changed because of the seiche. In other words, they wanted to measure the amplitude and period of the seiche. The amplitude is the height of a wave from its midpoint, or equilibrium. The amplitude can be calculated as half of the water level change from its highest and lowest point in a cycle. The length of time it takes to complete one full back-and-forth cycle is called the period. You can track the period of the seiche by how much time has passed from one peak to the next peak.

Over their summer break, Gena and Ali started to plan how they could document changes in water levels in their hometown. With permission, Gena and Ali placed a sensor inside a boathouse that was protected from wave action. The sensor measured the distance to the nearest object and was set to collect a data point every six minutes. Gena and Ali placed the sensor so that it faced the surface of the water. That way, it would document changes in the water level throughout time.

Featured scientists: Gena (she/her) and Ali Gephart (she/her), Bayfield High School.

Written by: Richard Erickson, Bayfield High School, and Hannah Erickson, Boston Public Schools.

Flesch–Kincaid Reading Grade Level = 8.8

Additional teacher resources related to this Data Nugget include:

  • Here is a link to learn more about the physics of waves.
  • Visit this NOAA website to learn more about seiche behavior and characteristics.
4.13.23

Surviving the flood

Andrew writing down field notes in an urban stream.

The activities are as follows:

When imagining a stream, you may think of pristine water flowing through a forest or mountain valley. However, streams are found everywhere, including cities. Many of these urban streams run through a pipe, disappear underground, or are filled with water that doesn’t seem to be moving. These streams are often overlooked because they appear more like deep ditches or canals, but they play an important role in water management.

When rain falls in a forest, it flows through the soil, moving in the small spaces between soil particles. Eventually, it reaches a stream. This journey slows the water and prevents flooding. However, when rain falls in an urban area, it often does not move through soil before getting to a stream. Urban streams are instead surrounded by buildings, roads, and parking lots. Water races over these surfaces, causing rapid flooding. This water, called stormwater runoff, can cause a stream to go from ankle-deep to over your head in just a few hours!

A team of stream ecologists, including graduate student Andrew and his advisor Dave, wanted to see whether stormwater floods disturb urban stream ecosystems. Urban streams provide important habitat for many species – fish, insects, crustaceans, bacteria, and algae. Andrew and Dave have observed how large stormwater floods can sweep algae off rocks or bury algae with sediment that is washed in from parking lots. However, algae and other organisms in urban streams are used to living in a habitat with frequent disturbance and can cling to the rocks during small floods.

Andrew downloading data from the data loggers.

Andrew and Dave focused their research on algae because they are an important part of aquatic ecosystems. Algae use energy from sunlight and building blocks from carbon dioxide gas to create sugar and oxygen. This process is called photosynthesis. By photosynthesizing during the day and not at night, algae cause large changes in the amount of oxygen in stream water. Taking a closer look at these daily oxygen changes, you can see how well algae are doing and how healthy a stream is.

Andrew and Dave monitored daily changes in the stream by using sensors that collect oxygen concentrations every 10 minutes.

Andrew and Dave also needed to measure the intensity of flooding during different kinds of storms. They used a measure called discharge, which accounts for both the amount of water flowing in a stream and how fast it’s moving. During a rain event, the time when the most water at the highest speed is rushing through the stream is called the peak discharge. For this measure, Andrew and Dave had some help from the United States Geological Survey, which has instruments in streams and rivers all over the country measuring discharge all the time. Looking at this dataset, Andrew detected a total of 13 storm events of different sizes during a one-year study period.

When the peak discharge is very high, the fast-moving water and flooding disturb algae by sweeping them off rocks and other surfaces, sending them downstream with the flow of water, and the algae are unable to photosynthesize. To answer their question, they looked at the oxygen concentrations for the day leading up to and following the 13 storms that Andrew identified. The difference in oxygen produced by algae before and after storms is a simple way to look at whether the algae resist the flooding or are disturbed by the flooding. If the oxygen concentration is the same after the storm as it was before the storm, the algae were resistant. If oxygen is lower after the storm than before the storm, that means that the algae were disturbed. Andrew and Dave thought that intense storms with high discharge will disrupt the algae more, resulting in lower oxygen concentrations after a storm than before a storm.

Featured scientists: Andrew Blinn (he/him) and Dave Costello (he/him) from Kent State University

The research and data found in this activity come from the STORMS project, which investigates how stormwater management decisions influence hydrology and stream health in tributaries of the Cuyahoga River Watershed of Ohio.

Flesch–Kincaid Reading Grade Level = 10.3

Additional teacher resources related to this Data Nugget include:

3.16.23

Benthic buddies

Danny and Kaylie sampling benthic animals

The activities are as follows:

Lagoons are areas along the coast where a shallow pocket of sea water is separated from the ocean most of the time. During some events, like high tides, the ocean water meets back up with the lagoon. Coastal lagoons are found all over the world – even in the most northern region of Alaska, called the High Arctic!

These High Arctic lagoons go through many extreme changes each season. In April, ice completely covers the surface. The mud at the bottom of the shorelines is frozen solid. In June, the ice begins to break up and the muddy bottoms of the lagoons begin to thaw. The melting ice adds freshwater to the lagoons and lowers the salt levels. In August, lagoon temperatures continue to rise until there is only open water and soft mushy sediment.

You would think these harsh conditions would make High Arctic lagoons not suitable to live in. However, these lagoons support a surprisingly wide range of marine organisms! Marine worms, snails, and clams live in the muddy sediment of these lagoons. This habitat is also called the bottom, or benthic, environment. Having a rich variety of benthic animals in these habitats supports fish, which migrate along the shoreline and eat these animals once the ice has left. And people who live in the Arctic depend on fishing for their food.

Ken, Danny, and Kaylie are a team of scientists from Texas interested in learning more about how the extreme seasons of the High Arctic affect the marine life that lives there. They want to know whether the total number of benthic species changes with the seasons. Or does the benthic community of worms, snails, and clams stay constant throughout the year regardless of ice, freezing temperatures, and large changes in salt levels? The science team thought that the extreme winter conditions in the Arctic lagoons cause a die-off each year, so there would be fewer species found at that time. Once the ice melts each year, benthic animals likely migrate back into the lagoons from deeper waters and the number of species would increase again.

Ken, Danny, and Kaylie had many discussions about how they could answer their questions. They decided the best approach would be to travel to Alaska to take samples of the benthic animals. To capture the changes in lagoon living conditions, they would need to collect samples during the three distinct seasons.

Benthic organisms from a sample

The science team chose to sample Elson Lagoon because it is in the village of Utqiaġvik, Alaska and much easier to reach than other Arctic lagoons. They visited three times. First, in April, during the ice-covered time, again in June when the ice was breaking up, and a final time in summer when the water was warmer. In April, they used a hollow ice drill to collect a core sample of the frozen sediment beneath the ice. In June and August, they deployed a Ponar instrument into the water, which snaps shut when it reaches the lagoon bottom to grab a sample. Each time they visited the lagoon, they collected two sediment samples.

Back in the lab, they rinsed the samples with seawater to remove the sediment and reveal the benthic animals. The team then sorted and identified the species present. They recorded the total number of different species, or species richness, found in each sample.

Featured scientists: Ken Dunton, Daniel Fraser, and Kaylie Plumb from the University of Texas Marine Science Institute

Written by: Maria McDonel from Flour Bluff and Corpus Christi Schools

Flesch–Kincaid Reading Grade Level = 8.9

Additional teacher resources related to this Data Nugget include:

9.6.22

Changing climates in the Rocky Mountains

Lower elevation site in the Rocky Mountains: Temperate conifer forest. Photo Credit: Alice Stears.

The activities are as follows:

Each type of plant needs specific conditions to grow and thrive. If conditions change, such as temperature or the amount of precipitation, plant communities may change as well. For example, as the climate warms, plant species might start to shift to higher latitudes to follow the conditions where they grow best. But what if a species does well in cold climates found at the tops of mountains? Because they have nowhere to go, warming puts that plant species at risk.  

To figure out if species are moving, we need to know where they’ve lived in the past, and if climates are changing. One way that we can study both things is to use the Global Vegetation Project. The goal of this project is to curate a global database of plant photos that can be used by educators and students around the world. Any individual can upload photos and identify plant species. The project then connects each photo to information on the location’s biome, ecoregion, and climate, including data tracking precipitation and temperature over time. The platform can also be used to explore how the climates of different regions are changing and use that information to predict how plant communities may change. 

Daniel is a scientist who is interested in sharing the Global Vegetation Project data with students. Daniel became interested in plants and vegetation when he learned in college that you can simply walk through the woods and prairie, collect wild seeds, germinate the plants, and grow them to restore degraded landscapes. Plants set the backdrop for virtually every landscape that we see. He thinks plants deserve our undivided attention.

Daniel and his team wanted to create a resource where students can look deeper into plant communities and their climates. Much of the inspiration for the Global Vegetation Project came from the limitations to undergraduate field research during the COVID-19 pandemic. Students in ecology and botany classes, who would normally observe and study plants in the field, were prevented from having these opportunities. By building an online database with photos of plants, students can explore local plants without having to go into the field and can even see plants from faraway places. 

Daniel’s lab is based in the Rocky Mountains in Wyoming, where the plants are a showcase in both biodiversity and beauty. These communities deal with harsh conditions: cold, windy and snowy winters, hot and dry summers, and unpredictable weather during spring and fall. The plants rely on winter snow slowly melting over spring and into summer, providing moisture that can help them survive the dry summers. 

The Rocky Mountains are currently facing many changes due to climate change, including drought, increased summer temperatures, wildfires, and more. This creates additional challenges for the plants of the Rockies. Drought reduces the amount of precipitation, decreasing the amount of water available to plants. In addition, warmer temperatures in winter and spring shift more precipitation to rain instead of snow and melts snow more quickly. Rain and melted snow rapidly move through the landscape, becoming less available to plants in need. On top of all this, hotter, drier summers further decrease the amount of water available, stressing plants in an already harsh environment. If these trends continue, there could be significant impact on the types of plants that are able to grow in the Rocky Mountains. These changes will have an impact on the landscape, organisms that rely on plants, and humans as well.

Daniel and his colleagues pulled climate data from a Historic period (1961-2009) and Current period (2010-2018). They selected two locations in Wyoming to focus on: a lower elevation montane forest and a higher elevation site. To study climate, they focused on temperature and precipitation because they are important for plants. They wanted to study how temperature and precipitation patterns changed overall and how they changed in different seasons. They predicated temperatures would be higher in the Current period compared to the Historic period in both locations. For precipitation, they predicted there would be drier summers and wetter springs.

Featured scientist: Daniel Laughlin from The University of Wyoming. Written by: Matt Bisk.

Flesch–Kincaid Reading Grade Level = 10.5

Additional teacher resource related to this Data Nugget:

8.20.22

Nitrate: Good for plants, bad for drinking water

Evelyn is a scientist at the University of Minnesota. She studies nitrate pollution and how growing perennial crops may prevent it from entering our drinking water.

The activities are as follows:

Nitrogen is the most abundant element in our atmosphere. All living things need nitrogen to live and grow, but plants and animals can’t use the atmospheric form. Instead, many plants extract nitrogen from the soil and in the case of crops, we supply nitrogen through fertilizer, in a form called nitrate.

Nitrate dissolves well in water. This helps make it easy for plants to use, but it can also end up in rivers and groundwater. Groundwater with just 10 milligrams of nitrate per liter is not safe to drink because it can lead to a higher risk of cancer and birth defects. It is really expensive to remove nitrate from drinking water. Towns whose groundwater is contaminated must either pay to remove it or find a new drinking water source. Virtually all nitrate pollution comes from fertilizers used on crops, so one way to address this problem is to change the way we farm.

Annual plants live for just one season and typically have smaller shallower root systems than perennial plants, which live for multiple seasons. Most farmland grows annuals like corn and soybeans, but we get some of our food from perennials like apples, hazelnuts, and raspberries. Perennials stay in the ground all year and start growing right away in the spring before annual crops are even planted. Perennial grasses are particularly good at growing deep roots and taking up lots of nitrate from the soil. If we could produce more food from perennial plants instead of annual plants, crops may absorb enough nitrate to prevent it from getting into our drinking water.

For twenty years, researchers at The Land Institute in Kansas and at the University of Minnesota have been working on a new perennial grain crop called Kernza®, the seeds from a plant called intermediate wheatgrass. Kernza® can be used like wheat or rye, but it has a larger, deeper root system than regular annual wheat. Perennial plants’ deep roots are really good at absorbing dissolved nitrate in soil, so scientists wanted to study Kernza® in the field to see if it would prevent nitrate getting into groundwater.

Evelyn is one of these researchers. She grew up in Minneapolis, Minnesota and as a high school student, she was surprised to learn that agriculture has a huge impact on soil and water quality, wildlife habitat, and biodiversity. She wanted to help protect the environment, so she studied Food Systems at the University of Minnesota. A few years later, she joined a project that involved planting Kernza® in rural areas to prevent and reduce nitrate contamination of drinking water. Farmers, city officials, water managers, and scientists worked together to find solutions. This project inspired Evelyn to study Kernza® and nitrate for her master’s degree.

In her experiment, Evelyn planted plots of Kernza® (foreground) and plots with a corn-soybean rotation (background). This photo was taken in a corn year. Lysimeters are used to collect groundwater samples. The white posts are holding up the lysimeter sampling tubes.

To see if Kernza® helped absorb more nitrate from soil than annual crops, Evelyn and her colleagues ran an experiment. They planted plots of Kernza® and other plots that rotated between corn and soybean every year. Plots with Kernza® and corn were fertilized with nitrogen. Soybean plots were not fertilized.

In the plots, they installed lysimeters: long tubes that go down several feet to collect soil water from below where most plant roots can reach it. Soil water is the water that sits between soil particles. It can be taken up by plant roots or trickle down into the groundwater that is used for drinking wells. Once it moves deeper than a plant’s roots, it can’t be taken up and is very likely to reach the groundwater. Evelyn took water samples from the lysimeters every ten days and analyzed them for nitrate concentration.  If more nitrate is found in soil water under corn and soybean plots than Kernza®, this would be good evidence that Kernza® takes up more nitrate and helps protect groundwater.

Featured scientist: Evelyn Reilly (she/her) from University of Minnesota

Flesch–Kincaid Reading Grade Level = 10.9

6.17.22

Going underground to investigate carbon locked in soils 

Mineral-associated organic matter (MAOM) at the bottom of a test tube in a salt solution.

The activities are as follows:

Soil is an important part of the carbon cycle because it traps carbon, keeping it out of the atmosphere and locked underground. At a global level, the amount of carbon stored by soil is more than is found in all of the plants and the atmosphere combined. Carbon trapped underground does not contribute to the rising carbon dioxide concentration in our atmosphere that leads to climate change. For decades, scientists have been researching how much carbon our soils can store to understand its role in slowing the pace of climate change.

Carbon enters the soil when plants and animals die, and their organic matter is decomposed by soil bacteria and fungi. Sometimes it is broken down into very small molecules. These molecules become attached to minerals in the soil, like clay particles. We call this mineral-associated organic matter (MAOM). The carbon is connected to minerals with very strong chemical bonds. Because these bonds are hard to break, the carbon stays in the soil for long periods of time and accumulates on clay minerals. 

Some studies have shown that the carbon in MAOM can be trapped in soils for thousands of years! When more of the carbon in the soil is attached to minerals and locked in the soil for longer time periods, the ecosystem is serving an important role in keeping carbon out of the atmosphere. 

Ashley in the lab, using a saltwater solution to isolate mineral-associated organic matter (MAOM) from soil samples.

Ashley is working to understand how much stable carbon there is in soils, and the role of climate. Microbes work faster in warmer and wetter conditions, which results in quicker decomposition. Ashley thought this rapid decomposition would cause organic matter to be broken down into smaller particles sooner. Therefore, she thought that in warmer or wetter environments, more soil carbon would attach to minerals and become stable MAOM. In colder or drier environments, she expected this process to happen more slowly, leading to a smaller amount of MAOM in the soil.

To test these ideas, Ashley used soil samples from forests with different climates throughout the Eastern United States. Soil samples were collected from New Hampshire to Alabama by teams of researchers using the same sampling protocol. The samples were mailed to Ashley’s lab at Indiana University for analysis. Ashley measured the amount of MAOM in each soil sample by taking advantage of a key feature: MOAM is heavy! Ashley submerged each soil sample in a saltwater solution, and the parts that floated were discarded, while the parts that sunk to the bottom were classified as MAOM. She then rinsed the salt off and measured the amount of carbon in the MAOM with an instrument called an elemental analyzer. She compared this number to the amount of carbon in the whole soil sample to calculate what percentage of the total soil carbon was attached to minerals.

Featured scientist: Ashley Lang from Indiana University

Flesch–Kincaid Reading Grade Level = 10.8

Additional teacher resources related to this Data Nugget:

3.31.22

Salty sediments? What bacteria have to say about chloride pollution

Lexi taking water quality measurements at Cedar Creek in Cedarburg, WI.

The activities are as follows:

In snowy climates, salt is applied to roads to help keep them safe during the winter. Over time, salt – in the form of chloride – accumulates in snowbanks. Once temperatures begin to warm in the spring, the snow melts and carries chloride to freshwater lakes, streams, and rivers. This runoff can quickly increase the salt concentration in a body of water. 

In large amounts, salt in the water is harmful to aquatic organisms like fish, frogs, and invertebrates. However, there are some species that thrive with lots of salt. Salt-loving bacteria, also known as halophiles, grow in extreme salty environments, like the ocean. Unlike other bacteria and organisms that cannot tolerate high salinity, halophiles use the salt in the environment for their day-to-day cellular activities. 

Lexi is a freshwater scientist who is interested in learning more about how ecosystems respond to this seasonal surge of chloride in road salts. She thought that there may be enough chloride from the road salt after snowmelt to change the bacteria community living in the sediment. More salt would support halophiles and likely harm the species that cannot tolerate a lot of salt. 

By taking a water sample and measuring the chloride concentration, we can see a snapshot in time of how toxic the levels are to organisms. However, the types of bacteria in sediments take a while to change. Halophiles may be able to tell us a long-term story of how aquatic organisms respond to chloride pollution. Lexi’s main goal is to use the presence of halophiles as a measure of how much chloride has impacted the health and water quality of river or stream ecosystems. This biological tool could also help cities identify areas that may be getting salted beyond what is necessary to keep roads safe.

Lexi expected that there would be few, or maybe no, halophiles in rural areas where there are not many roads. She also thought halophiles would be widespread in urban environments where there are many roads. Because salt impacts the streams year after year, she expected that halophiles would become permanent members of the microbial community and increase in winter and spring. Therefore, she also wanted to track whether halophiles remain in the sediment throughout the year, increasing in numbers when salt levels become high. 

She began to sample sediments from two different rivers in Southeastern Wisconsin. The urban Kinnickinnic River site is in Milwaukee, WI, and the Menomonee River site is in a rural environment outside of the city. She selected these sites because they offer a good comparison. Because there are more roads, and thus saltier snowmelt, the Kinnickinnic site in the city should have higher chloride concentrations than the Menomonee site. 

When visiting her sites throughout the year, Lexi collected multiple water and sediment samples. Every time she visited, she also recorded important water quality characteristics such as pH, conductivity, and temperature of the water. She then brought the samples to the laboratory and analyzed each for its chloride concentration. To measure the quantity of halophiles in the sediment, Lexi used a process where the sediment is shaken in water to separate the bacteria from the sediment and suspend them in the water. Samples from the water were then plated on a growth medium that contained a very high salt concentration. Because the growth medium was so salty, Lexi knew that if bacteria colonies grew on the plate, they would most likely be halophiles because most bacteria do not thrive in salty environments. Lexi counted the number of bacteria colonies that grew on the plates for each sample she had collected.

Featured scientist: Lexi Passante from the University of Wisconsin-Milwaukee

Flesch–Kincaid Reading Grade Level = 12.0

Some videos about Lexi and her research:

Additional teacher resources related to this Data Nugget:

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