The mystery of Plum Island Marsh

Scientist, Harriet Booth, counting and collecting mudsnails from a mudflat at low tide.

Scientist, Harriet Booth, counting and collecting mudsnails from a mudflat at low tide.

The activities are as follows:

Salt marshes are among the most productive coastal ecosystems. They support a diversity of plants and animals. Algae and marsh plants use the sun’s energy to make sugars and grow. They also feed many invertebrates, such as snails and crabs, which are then eaten by fish and birds. This flow of energy through the food web is important for the functioning of the marsh. Also important for the food web is the cycle of matter and nutrients. The waste from these animals, and eventually their decaying bodies, recycle matter and nutrients, which can be used by the next generation of plants and algae. Changes in any links in the food chain can have cascading effects throughout the ecosystem.

Today, we are adding large amounts of fertilizers to our lawns and agricultural areas. When it rains, these nutrients run off into our waterways, ponds, and lakes. If the added nutrients end up in marshes, marsh plants and algae can then use these extra nutrients to grow and reproduce faster. Scientists working at Plum Island Marsh wanted to understand how these added nutrients affect the marsh food web, so they experimentally fertilized several salt marsh creeks for many years. In 2009, they noticed that fish populations were declining in the fertilized creeks.

View of a Plum Island salt marsh.

View of a Plum Island salt marsh.

Fertilizer does not have any direct effect on fish, so the scientists wondered what the fertilizer could be changing in the system that could affect the fish. That same year they also noticed that the mudflats in the fertilized creeks were covered in mudsnails, far more so than in previous years. These mudsnails eat the same algae that the fish eat, and they compete for space on the mudflats with the small invertebrates that the fish also eat. The scientists thought that the large populations of mudsnails were causing the mysterious disappearance of fish in fertilized creeks by decreasing the number of algae and invertebrates in fertilized creeks.

A few years later, Harriet began working as one of the scientists at Plum Island Marsh. She was interested in the mudsnail hypothesis, but there was yet no evidence to show the mudsnails were causing the decline in fish populations. She decided to collect some data. If mudsnails were competing with the invertebrates that fish eat, she expected to find high densities of mudsnails and low densities of invertebrates in the fertilized creeks. In the summer of 2012, Harriet counted and collected mudsnails using a quadrat (shown in the photo) and took cores down into the mud to measure the other invertebrates in the mudflats of the creeks. She randomly sampled 20 locations along a 200-meter stretch of creek at low tide. The data she collected are found below and can help determine whether mudsnails are responsible for the disappearance of fish in fertilized creeks.

Mudsnails on a mudflat, and the quadrat used to study their population size.

Mudsnails on a mudflat, and the quadrat used to study their population size.

Featured scientist: Harriet Booth from Northeastern University

Flesch–Kincaid Reading Grade Level = 10.2

Click here for a great blog post by Harriet detailing her time spent in the salt marsh: Harriet Booth: Unraveling the mysteries of Plum Island’s marshes

If your students are looking for more information on trophic cascades in salt marsh ecosystems, check out the video below!

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Invasive reeds in the salt marsh

Culverts run under roads and allow water from the ocean to enter a marsh. Phragmites can be seen growing in the background.

Culverts run under roads and allow water from the ocean to enter a marsh. Phragmites can be seen growing in the background.

The activities are as follows:

Phragmites australis is an invasive reed, a type of grass that grows in water. Phragmites is taking over saltwater marshes in New England, or wetland habitats near the Atlantic Ocean coast. Phragmites does so well it crowds out native plants that once served as food and homes for marsh animals. Once Phragmites has invaded, it is sometimes the only plant species left! Phragmites does best where humans have disturbed a marsh, and scientists were curious why that might be. They thought that perhaps when a marsh is disturbed, the salinity, or amount of salt in the water, changes. Phragmites might be able to survive after disturbances that cause the amount of salt in the water to drop, but becomes stressed when salinity is high.

Students collecting data on the plant species present in the marsh using transects. Every 1m along the tape, students observe which plants are present. Phragmites is the tall grass that can be seen growing behind the students.

Students collecting data on the plant species present in the marsh using transects. Every 1m along the tape, students observe which plants are present. Phragmites is the tall grass that can be seen growing behind the students.

Fresh water in a marsh flows from the upstream source to downstream. Saltwater marshes end at the ocean, where freshwater mixes with salty ocean water. One type of disturbance is when a road is cut through a marsh. Upstream of the road, the marsh is cut off from the salt waters from the ocean, so only fresh water will enter and salinity will drop. Downstream of the road, the marsh is still connected to the ocean and salinity should be unaffected by the disturbance. Often, a culvert (a pipe that runs under the road) is placed to allow salt water to pass from the ocean into the marsh. The amount of ocean water flowing into the marsh is dependent on the diameter of the culvert.

Students at Ipswich High School worked with scientists from the Mass Audubon, a conservation organization, to look at the Phragmites in the marsh. They looked at an area where the salinity in the marsh changed after a road was built. They wanted to know if this change would affect the amount of Phragmites in that marsh. In 1996, permanent posts were placed 25 meters apart in the marsh. That way, scientists could collect data from the same points each year. At these posts, students used transects, a straight line measured from a point to mark where data is collected. Then they collected data on all the plants that were found every meter along the transects. Data has been collected at these same points since 1996. In 2005, an old 30cm diameter culvert was replaced with two 122cm culverts. These wider culverts allow much more salty ocean water to flow under the road and into the marsh. Students predicted that after the culverts were widened, more ocean water would enter the marsh. This would make salinity go up, making it harder for Phragmites to grow, and it would decline in numbers. Students continued to survey the plants found along transects at each permanent post and documented their findings.

Featured scientists: Lori LaFrance from Ipswich High School, Massachusetts and Liz Duff from Mass Audubon. This study was part of the PIE-LTER funded by the NSF.

Flesch–Kincaid Reading Grade Level = 9.0

To access the original data presented in this activity, and collected by students, access Mass Audubon’s Vegetation Data, available online. To access the salinity data related to this activity, and collected by students, access Mass Audubon’s Salinity Data, available online. Scroll down to “Ipswich, MA, Town Farm Road” for data from the site discussed here.

View of the two new culverts.

View of the two new culverts.

The old pipe that was removed.

The old pipe that was removed, and the new culvert.

 

 

 

Arial view of the upstream and downstream research sites.

Arial view of the upstream and downstream research sites.

Springing forward

Scientist Shaun collecting phenology data in the climate change experiment. He is recording the date that the first flowers emerge for dame’s rocket.

Sean Mooney, a high school researcher, collecting phenology data in the climate change experiment. He is recording the date that the first flowers emerge for dame’s rocket.

The Reading Level 1 activities are as follows:

The Reading Level 3 activities are as follows:

Every day we add more greenhouse gases to our air when we burn fossil fuels like oil, coal, and natural gas. Greenhouse gasses trap the sun’s heat, so as we add more the Earth is heating up! What does climate change mean for the species on our planet? The timing of life cycle events for plants and animals, like flowering and migration, is largely determined by cues organisms take from the environment. The timing of these events is called phenology. Scientists studying phenology are interested in how climate change will influence different species. For example, with warming temperatures and more unpredictable transitions between seasons, what can we expect to happen to the migration timings of birds, mating seasons for animals, or flowering times of plants?

Scientists collecting phenology data in the climate change experiment. They are recording the date that the first flowers emerge for dame’s rocket.

Scientists collecting phenology data in the climate change experiment.

Plants are the foundation for almost all life on Earth. Through photosynthesis, plants produce the oxygen (O2) that we breathe, food for their own growth and development, food for animals and microbes, and crops that provide food and materials for human society. Because plants are so important to life, we need to find out how climate change could affect them. One good place to start is by looking at flowering plants, guided by the question, how will increased temperatures affect the phenology of flowering? One possible answer to this question is that the date that flowers first emerge for a species is driven by temperature. If this relationship is real, we would expect flowers to emerge earlier each year as temperatures increase due to climate change. But if flowers come out earlier and earlier each year, this could greatly impact plant reproduction and could cause problems for pollinators who count on plants flowering at the same time the pollinators need the pollen for food.

Shaun, Mark, Elizabeth, and Jen are scientists in Michigan who wanted to know if higher temperatures would lead to earlier flowering dates for plants. They chose to look at flowers of dame’s rocket, a leafy plant that is related to the plants we use to make mustard! Mark planted dame’s rocket in eight plots of land. Plots were randomly assigned to one of two treatments. Half of the plots were left to experience normal temperatures (normal), while the other four received a heating treatment to simulate climate change (heated). Air temperatures in heated plots increased by 3°C, which mimics climate change projections for what Michigan will experience by the end of the century. Mark, Elizabeth, and Jen measured the date that each plant produced its first flower, and the survival of each plant. The scientists predicted that dame’s rocket growing in the heated plots would flower earlier than those in the normal plots.

 Featured scientists: Shaun Davis from Thornapple Kellogg Middle School and Mark Hammond, Elizabeth Schultheis, and Jen Lau from Michigan State University

Flesch–Kincaid Reading Grade Level = The Reading Level 3 activity has a score of 9.2; the Level 1 has a 6.4.

Flowers of Hesperis matronalis (dame’s rocket), a species of mustard that was introduced to the U.S. from Eurasia.

Flowers of Hesperis matronalis (dame’s rocket), a species of mustard that was introduced to the U.S. from Eurasia.

Additional teacher resources related to this Data Nugget include:

  • If you would like your students to interact with the raw data, we have attached the original data here. The file also includes weather data over the course of the experiment if students want to ask and explore independent questions.
  • For a lesson plan that uses citizen science phenology datasets to examine changes in phenology over 30+ year timespans, and address the scientific question, “Do we see evidence for climate change in the phenology of plants and animals?”, click here.
  • Many phenology datasets are freely available online (many collected by citizen scientists). These datasets are extremely useful because scientists (and your students!) can examine average trends in timing shifts over periods of decades and often in different regions. Phenology datasets available online:
  • NY Times article on research showing what happens when climate change shifts phenology – “5 Plants and Animals Utterly Confused by Climate Change

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Float down the Kalamazoo River

Morrow Lake, a reservoir created along the Kalamazoo River. The water is held in a reservoir by a dam. When water flows into the reservoir it slows, potentially letting some of the total suspended solids settle to the bottom of the river.

Morrow Lake, a reservoir created along the Kalamazoo River. The water is held in a reservoir by a dam. When water flows into the reservoir it slows, potentially letting some of the total suspended solids settle to the bottom of the river.

The activities are as follows:

Ever since she was a kid, rivers have fascinated Leila. One of her hobbies is to kayak and canoe down the Kalamazoo River in Michigan, near where she lives. For her work, she researches all the living things in the river and how humans affect them. She is especially interested in changes in the river food web, caused by humans building dams along the river, and an oil spill in 2010.

Leila knows there is a lot more in river water than what meets the eye! As the river flows, it picks up bits of dead plants, single-celled algae, and other living and nonliving particles from the bottom of the river. The mix of all these particles is called total suspended solids (TSS) because these particles are suspended in the river water as it flows. The food web in the Kalamazoo River depends on the particles that are floating in the water. Invertebrates eat decomposing leaves and algae, and fish eat the invertebrates.

Leila showing off some of the cool invertebrates that can be found in the Kalamazoo River.

Leila showing off some of the cool invertebrates that can be found in the Kalamazoo River.

As you float down the river, particles settle to the river bottom and new ones are picked up. The amount of suspended solids in a river is influenced by how fast the water in the river is flowing. The faster the water flows, the more particles are picked up and carried down the river. The slower the water flows, the more particles will settle to the bottom. Discharge is a measure of how fast water is flowing. You can think about discharge as the number of cubes (one foot on each side) filled with water that pass by a point every second. During certain times of the year, water flows faster and there is more discharge. In spring, when the snow starts melting, a lot of water drains from the land into the river. There also tends to be a lot more rain in the fall. Things humans build on the river can also affect discharge. For example, we build dams to generate hydroelectric power by capturing the energy from flowing water. Dams slow the flow of river water, and therefore they may cause some of the suspended solids to settle out of the water and onto the bottom of the river.

Leila wanted to test how a dam that was built on the Kalamazoo River influenced total suspended solids. If the dam is reducing the amount of total suspended solids, it could have negative effects on the food chain. She was also curious to see if the dam has different effects depending on the time of year. On eight different days from May to October in 2009, Leila measured total suspended solids at two locations along river. She collected water samples upstream of the dam, before the water enters the reservoir, and samples downstream after the water has been in the reservoir and passed over the dam. She also measured discharge downstream of the dam.

KalamazooRiver

Featured scientist: Leila Desotelle from Michigan State University

Flesch–Kincaid Reading Grade Level = 8.7

If your students are looking for more information on how the amount of water flowing in the river affects the food chain and the health of the ecosystem overall, check out the video below!