wetland ‣ Data Nuggets

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.

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.

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

Arial view of the upstream and downstream research sites.

Marvelous mud

You can tell that the mud in this picture is high in organic matter because it is dark brown and mucky (in real life you’d be able to smell it, too!)

The activities are as follows:

The goopy, mucky, often stinky mud at the bottom of a wetland or lake is a very important part of the ecosystem. Wetland mud is much more than just wet dirt. For example, many species of microbes live in the wetland mud where they decompose (breakdown) dead plant and animal material to obtain energy. This dead plant and animal material is called organic matter. However, the wetland mud microbes do not have all the oxygen they need to decompose the plant and animal tissues quickly and efficiently. Because of this, the dead material in wetland mud decomposes much more slowly than similar dead material in dry soil.

A successful core! You can see that the tube has mud, as well as some of the water from the wetland that was on top of the mud.

As a graduate student, Lauren became fascinated with wetland mud and its interesting properties. She wanted to know how important all the mud and its organic matter is for wetlands. By talking with other members of her lab and reading scientific papers, Lauren learned that wetland mud can often be high in the element phosphorus and that phosphorus acts as a fertilizer for plants, including wetland plants and algae. However, nutrients, such as phosphorus can build up in wetland mud. Lauren thought it might be possible that the organic matter in the mud was the source of all the phosphorus in some wetlands. She predicted that wetlands with more organic matter would have more phosphorus. If her data support her hypothesis, it could mean that organic matter is very important for wetlands, because nutrients are needed for algae and plants to grow.

Although most mud is high in organic matter and nutrients, not all mud is the same. There is natural variation in the amount of organic matter and nutrients from place to place. Even within the same location mud can be very different in spots. Lauren used this variability to test her ideas. She measured organic matter and phosphorus in mud from 16 freshwater locations (four lakes, five ponds, and seven wetlands). She took cores that allowed her to sample mud deep into the ground. She then brought her cores back to the lab and measured organic matter and phosphorus levels in her samples.

Featured scientist: Lauren Kinsman-Costello from Kent State University

Flesch–Kincaid Reading Grade Level = 9.8

More photos associated with this research can be found here. There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below:

Kinsman-Costello LE, J O’Brien, SK Hamilton (2014) Re-flooding a Historically Drained Wetland Leads to Rapid Sediment Phosphorus Release. Ecosystems 17:641-656

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Invasive reeds in the salt marsh

Marvelous mud