5.14.25

PFAS: Our forever problem

This image has an empty alt attribute; its file name is gary-headshot.png
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

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:

2.4.21

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.