Marsh makeover

A saltmarsh near Boston, MA being restored after it was degraded by human activity.

The activities are as follows:

Salt marshes are diverse and productive ecosystems, and are found where the land meets the sea. They contain very unique plant species that are able to tolerate flooding during high tide and greater salt levels found in seawater. Healthy salt marshes are filled with many species of native grasses. These grasses provide food and nesting grounds for lots of important animals. They also help remove pollution from the land before it reaches the sea. The grass roots protect the shoreline from erosion during powerful storms. Sadly today, humans have disturbed most of the salt marshes around the world. As salt marshes are disturbed, native plant biodiversity, and the services that marshes provide to us, are lost.

A very important role of salt marshes is that they are able to store carbon, and the amount they store is called their carbon storage capacity. Carbon is stored in marshes in the form of both dead and living plant tissue, called biomass. Marsh grasses photosynthesize, taking carbon dioxide out of the atmosphere and storing it in plant biomass. This biomass then falls into the mud and the carbon is stored there for a very long time. Salt marshes have waterlogged muddy soils that are low in oxygen. Because of the lack of oxygen, decomposition of dead plant tissue is much slower than it is in land habitats where oxygen is plentiful. All of this stored carbon can help lower the levels of carbon dioxide in our atmosphere. This means that healthy and diverse salt marshes are very important to help fight climate change.

However, as humans change the health of salt marshes, we may also change the amount of carbon being stored. As humans disturb marshes, they may lower the biodiversity and fewer plant species can grow in the area. The less plant species growing in the marsh, the less biomass there will be. Without biomass falling into the mud and getting trapped where there is little oxygen, the carbon storage capacity of disturbed marshes may go down.

Jennifer, working alongside students, to collect biomass data for a restored saltmarsh.

It is because of the important role that marshes play in climate change that Jennifer, and her students, spend a lot of time getting muddy in saltmarshes. Jennifer wants to know more about the carbon storage capacity of healthy marshes, and also those that have been disturbed by human activity. She also wants to know whether it is possible to restore degraded salt marshes to help improve their carbon storage capacity. Much of her work focuses on comparing how degraded and newly restored marshes to healthy marshes. By looking at the differences and similarities, she can document the ways that restoration can help increase carbon storage. Since Jennifer and her students work in urban areas with a lot of development along the coast, there are lots of degraded marshes that can be restored. If she can show how important restoring marshes is for increasing plant diversity and helping to combat climate change, then hopefully people in the area will spend more money and effort on marsh restoration.

Jennifer predicted that: 1) healthy marshes will have a higher diversity of native vegetation and greater biomass than degraded salt marshes, 2) restored marshes will have a lower or intermediate level of biomass depending on how long it has been since the marsh was restored, and 3) newly restored marshes will have lower biomass, while marshes that were restored further in the past will have higher biomass.

To test her predictions, Jennifer studied two different salt marshes near Boston, Massachusetts, called Oak Island and Neponset. Within each marsh she sampled several sites that had different restoration histories. She also included some degraded sites that had never been restored for a comparison. Jen measured the total number of different plant species and plant biomass at multiple locations across all study sites. These measurements would give Jen an idea of how much carbon was being stored at each of the sites.

Featured scientist: Jennifer Bowen from Northeastern University

Flesch–Kincaid Reading Grade Level = 11.0

When a species can’t stand the heat

An adult male tuatara. Photo by Scott Jarvie.

An adult male tuatara. Photo by Scott Jarvie.

The activities are as follows:

Tuatara are a unique species of reptile found only in New Zealand. Tuatara look like lizards but they are actually in their own reptile group. Tuatara are the only species remaining on the planet from this lineage, one that dates to the time of the dinosaurs! Tuatara are similar to tortoises in that they are extremely long-lived and can sometimes live over 100 years. Tuatara start reproducing when they are about 15–20 years old and they breed infrequently.

North Brother Island, one of the small New Zealand islands where tuatara are still found today.

North Brother Island, one of the small New Zealand islands where tuatara are still found today. Photo by Jo Monks.

The sex of tuatara is not determined by sex chromosomes (X or Y) as in humans. Instead, the temperature of the nest during egg development is the only factor that determines the sex of tuatara embryos. If the egg develops with a low temperature in the nest it will be female, but if it develops with a high temperature it will be male. This process happens in many other species, too, including some turtles, crocodiles, lizards, and fish. However, most species are the opposite of tuatara and produce females at the warmest temperatures.

Today, tuatara face many challenges. Humans introduced new predators to the large North and South Islands of New Zealand. Tuatara used to live on these main islands, but predators drove the island populations to extinction. Today, the tuatara survive only on smaller offshore islands where they can escape predation. Because many of these islands are small, tuatara can have low population numbers that are very vulnerable to a variety of risk factors. One of the current challenges faced by these populations is climate change. Similar to the rest of the world, New Zealand is experiencing higher and higher temperatures as a result of climate change, and the warm temperatures may impact tuatara reproduction.

Kristine collecting data on a tuatara in the field.

Kristine collecting data on a tuatara in the field. Photo by Sue Keall.

North Brother Island has a small population of tuatara (350–500 individuals) that has been studied for decades. Every single tuatara has been marked with a microchip (like the ones used on pet dogs and cats), which allows scientists to identify and measure the same individuals repeatedly across several years. In the 1990s, a group of scientists studying the tuatara on this island noticed that there were more males than females (60% males). The scientists started collecting data on the number of males and females so they could track whether the sex ratio, or the ratio of males and females in the population, became more balanced or became even more male-biased over time. The sex ratio is important because when there are fewer females in a population, there are fewer individuals that lay eggs and produce future offspring. Generally, a population that is highly male-biased will have lower reproduction rates than a population that is more balanced or is female-biased.

The fact that tuatara are long-lived and breed infrequently meant that the scientists needed to follow the sex ratio for many years to be sure they were capturing a true shift in the sexes over time, not just a short-term variation. In 2012, Kristine and her colleagues decided to use these long-term data to see if the increasing temperatures from climate change were associated with the changing sex ratio. They predicted that there would be a greater proportion of males in the population over time. This would be reflected in an unbalanced sex ratio that is moving further and further away from 50% males and 50% females and toward a male-biased population.

Graph showing mean annual temperatures for New Zealand, made by the National Institute of Water and Atmospheric Research. The y-axis represents the difference in that year’s mean temperature from the average temperature from 1981-2010. Red bars mean the year was warmer than average, and blue mean it was colder. The black line is the trend from 1909 to 2015 (0.92 ± 0.26°C/100 years).

Graph showing mean annual temperatures for New Zealand, made by the National Institute of Water and Atmospheric Research. The y-axis represents the difference in that year’s mean temperature from the average temperature from 1981-2010. Red bars mean the year was warmer than average, and blue mean it was colder. The black line is the trend from 1909 to 2015 (0.92 ± 0.26°C/100 years).

Featured scientists: Kristine Grayson from University of Richmond, Nicola Mitchell from University of Western Australia, and Nicola Nelson from Victoria University of Wellington

Flesch–Kincaid Reading Grade Level = 11.5

Additional teacher resources related to this Data Nugget:


kgAbout Kristine: Kristine L. Grayson received her Ph.D. in 2010 from the University of Virginia under the mentorship of Dr. Henry Wilbur. Her thesis used mark-recapture methods to examine migration behavior in a pond-breeding amphibian. She received an NSF International Research Fellowship to Victoria University of Wellington in New Zealand to conduct research on sex-ratio bias under climate change in tuatara, an endemic reptile. One of Kristine’s claims to fame is capturing the state record holding snapping turtle for North Carolina – 52 pounds! In addition to her passion for amphibian and reptile conservation, Kristine’s current work also examines the spread potential of gypsy moth, an invasive forest pest in North America. Kristine currently is an Assistant Professor in the Biology Department at University of Richmond.

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Make way for mummichogs

Collecting mummichogs and other fish out of research traps.

Collecting mummichogs and other fish out of research traps.

The activities are as follows:

Salt marshes are important habitats and contain a wide diversity of species. These ecosystems flood with salt water during the ocean’s high tide and drain as the tide goes out. Fresh water also flows into marshes from rivers and streams. Many species in the salt marsh can be affected when the movement of salt and fresh water across a tidal marsh is blocked by human activity, for example by the construction of roads. These restrictions to water movement, or tidal restrictions, can have many negative effects on salt marshes, such as changing the amount of salt in the marsh waters, or blocking fish from accessing different areas.

Local managers are working to remove tidal restrictions and bring back valuable habitat. At the same time, scientists are working to study how the remaining tidal restrictions impact fish populations. To do this, they measure the number of fish found upstream of tidal restrictions, which is the side connected to the river’s freshwater but cut off from the ocean when the restriction is in place. By taking measurements before and after the restriction is removed, scientists can study the impacts that the restriction had on fish populations

Mummichogs are a small species of fish that live in tidal marshes all along the Atlantic coast of the United States.

Mummichogs are a small species of fish that live in tidal marshes all along the Atlantic coast of the United States.

Mummichogs are a small species of fish that live in tidal marshes all along the Atlantic coast of the United States. They can be found in most streams and marsh areas and are therefore a valuable tool for scientists interested in comparing different marshes. The absence of mummichogs in a salt marsh is likely a sign that it is highly damaged.

In Gloucester, MA, students participating in Mass Audubon’s Salt Marsh Science Project are helping Liz and Robert use mummichogs to examine the health of a salt march. In 2002 and 2003 Liz, Robert, and the students set traps upstream of a road, which was acting as a tidal restriction. These traps collected mummichogs and other species of fish. The day after they set the traps, the students counted the number of each fish species found in the traps.

Students participating in Mass Audubon’s Salt Marsh Science Project Count fish at Eastern Point Wildlife Sanctuary, Gloucester, MA

Students participating in Mass Audubon’s Salt Marsh Science Project Count fish at Eastern Point Wildlife Sanctuary, Gloucester, MA

In December 2003, a channel was dug below the road to remove the tidal restriction and restore the marsh. From 2004 to 2007, students in the program continued to place traps in the same upstream location and collect data in the same way each year. Students then compared the number of fish from before the restoration to the numbers found after the restriction was removed. The students thought that once the tidal restriction was removed, mummichogs would return to the upstream locations in the marsh.

Featured scientists: Liz Duff and Robert Buchsbaum from Mass Audubon. Written by: Maria Maradianos, Samantha Scola, and Megan Wagner.

Flesch–Kincaid Reading Grade Level = 10.9

trap_locations

Additional teacher resources related to this Data Nugget:

Bye bye birdie? Part II

In Part I, you examined the patterns of total bird abundance at Hubbard Brook Experimental ForestThese data showed bird numbers at Hubbard Brook have declined since 1969. Is this true for every species of bird? You will now examine data for four species of birds to see if each of these species follows the same trend.

Red-eyed vireo in the Hubbard Brook Experimental Forest

Red-eyed vireo in the Hubbard Brook Experimental Forest

The activities are as follows:

It is very hard to study migratory birds because they are at Hubbard Brook only during their breeding season (summer in the Northern Hemisphere). They spend the rest of their time in the neotropics or migrating between their two homes. Therefore, it can be difficult to tease out the many variables affecting bird populations over their entire range. To start, scientists decided to focus on what they could study—the habitat types at Hubbard Brook and how they might affect bird populations.

Hubbard Brook Forest was heavily logged and disturbed in the early 1900s. Trees were cut down to make wood products, like paper and housing materials. Logging ended in 1915, and various plants began to grow back. The area went through secondary succession, which refers to the naturally occurring changes in forest structure that happen as a forest recovers after it was cut down or otherwise disturbed. Today, the forest has grown back. Scientists know that as the forest grew older, its structure changed: Trees grew taller, and there was less shrubby understory. It contains a mixture of deciduous trees that lose their leaves in the winter (about 80–90%; mostly beech, maples, and birches) and evergreen trees that stay green all year (about 10–20%; mostly hemlock, spruce, and fir).

Richard and his fellow scientists used their knowledge of bird species and thought that some bird species prefer habitats found in younger forests, while others prefer habitats found in older forests. They decided to look into the habitat preferences of four important species of birds—Least Flycatcher, Red-eyed Vireo, Black-throated Green Warbler, and American Redstart—and compare them to habitats available at each stage of succession.

  • Least Flycatcher: The Least Flycatcher prefers to live in semi-open, mid-successional forests. The term mid-successional refers to forests that are still growing back after a disturbance. These forests usually consist of trees that are all about the same age and have a thick canopy at the top with few gaps, an open middle canopy, and a denser shrub layer close to the ground.
  • Black-throated Green Warbler: The Black-throated Green Warbler occupies a wide variety of habitats. It seems to prefer areas where deciduous and evergreen forests meet and can be found in both forest types. It avoids disturbed areas and forests that are just beginning succession. This species prefers both mid-successional and mature forests.
  • Red-eyed Vireo: The Red-eyed Vireo breeds in deciduous forests as well as forests that are mixed with deciduous and evergreen trees. They are abundant deep in the center of a forest. They avoid areas where trees have been cut down and do not live near the edge. After an area is logged, it often takes a very long time for this species to return.
  • American Redstart: The American Redstart generally prefers moist, deciduous, forests with many shrubs. Like the Least Flycatcher, this species prefers mid-successional forests.

birds

Featured scientist: Richard Holmes from the Hubbard Brook Experimental Forest. Data Nugget written by: Sarah Turtle and Jackie Wilson.

Flesch–Kincaid Reading Grade Level = 10.2

A view of the Hubbard Brook Experimental Forest

A view of the Hubbard Brook Experimental Forest

Additional teacher resource related to this Data Nugget:

There are two publications related to the data included in this activity:

  • Holmes, R. T. 2010. Birds in northern hardwoods ecosystems: Long-term research on population and community processes in the Hubbard Brook Experimental Forest. Forest Ecology and Management doi:10.1016/j.foreco.2010.06.021
  • Holmes, R.T., 2007. Understanding population change in migratory songbirds: long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (Suppl. 2), 2-13

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Bye bye birdie? Part I

Male Black-throated Blue Warbler feeding nestlings. Nests of this species are built typically less than one meter above ground in a shrub such as hobblebush. Photo by N. Rodenhouse.

Male Black-throated Blue Warbler feeding nestlings. Nests of this species are built typically less than one meter above ground in a shrub such as hobblebush. Photo by N. Rodenhouse.

The activities are as follows:

The Hubbard Brook Experimental Forest is an area where scientists have collected ecological data for many years. It is located in the White Mountains of New Hampshire, and data collected in this forest helps uncover trends that happen over long periods of time. It is important to collect data on ecosystems over time, because these patterns could be missed with shorter experiments.

Richard Holmes is an avian ecologist who began this study because he was interested in how bird populations were responding to long-term environmental change.

Richard Holmes is an avian ecologist who began this study because he was interested in how bird populations were responding to long-term environmental change.

Each spring, Hubbard Brook comes alive with the arrival of migratory birds. Many migrate from wintering areas in the tropics to take advantage of the abundant insects and the long summer days of northern areas, which are beneficial when raising young. Avian ecologists, scientists who study the ecology of birds, have been keeping records on the birds that live in the experimental forest for over 40 years. These data are important because they represent one of the longest bird studies ever conducted!

Richard is an avian ecologist who began this study. He was interested in how bird populations were responding to long-term environmental changes in Hubbard Brook. Every summer since 1969, Richard takes his team of scientists, students, and technicians into the field to count the number of birds that are in the forest and identify which species are present. Richard’s team monitors populations of over 30 different bird species. They wake up every morning before the sun rises and travel to the far reaches of the forest. They listen for, look for, identify, and count all the birds they find. The scientists record the number of birds observed in four different study areas, each of which are 10 hectare in size – roughly the same size as 19 football fields! Each of the four study areas contain data collection points that are arranged in transects that run east to west along the valley. Transects are parallel lines along which the measurements are taken. Each transect is approximately 500m apart from the next. At each point on each transect, an observer stands for ten minutes recording all birds seen or heard during a ten minute interval, and estimates the distance the bird is from the observer. The team has been trained to be able to identify the birds by sight, but also by their calls. Team members are even able to identify how far away a bird is by hearing its call! The entire valley is covered three times a season. By looking at bird abundance data, Richard can identify trends that reveal how avian populations change over time.

Featured scientist: Richard Holmes from the Hubbard Brook Experimental Forest. Data Nugget written by: Sarah Turtle, Jackie Wilson and Elizabeth Schultheis.

Flesch–Kincaid Reading Grade Level = 10.6

A view of the Hubbard Brook Experimental Forest

A view of the Hubbard Brook Experimental Forest

Additional teacher resource related to this Data Nugget:

There are two publications related to the data included in this activity:

  • Holmes, R. T. 2010. Birds in northern hardwoods ecosystems: Long-term research on population and community processes in the Hubbard Brook Experimental Forest. Forest Ecology and Management doi:10.1016/j.foreco.2010.06.021
  • Holmes, R.T., 2007. Understanding population change in migratory songbirds: long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (Suppl. 2), 2-13

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Keeping up with the sea level

A view of salt marsh hay (Spartina patens) growing in a marsh

A view of salt marsh hay (Spartina patens) growing in a marsh

The activities are as follows:

Salt marshes are ecosystems that occur along much of the coast of New England in the United States. Salt marshes are very important – they serve as habitat for many species, are a safer breeding location for many fish, absorb nutrients from fertilizer and sewage coming from land and prevent them from entering the ocean, and protect the coast from erosion during storms.

Unfortunately, rising sea levels are threatening these important ecosystems. Sea level is the elevation of the ocean water surface compared to the elevation of the soil surface. Two processes are causing sea levels to rise. First, as our world gets warmer, ocean waters are getting warmer too. When water warms, it also expands. This expansion causes ocean water to take up more space and it will continue to creep higher and higher onto the surrounding coastal land. Second, freshwater frozen in ice on land, such as glaciers in Antarctica, is now melting and running into the oceans. Along the New England coast, sea levels have risen by 0.26 cm a year for the last 80 years, and by 0.4 cm a year for the last 20 years. Because marshes are such important habitats, scientists want to know whether they can keep up with sea level rise.

Researcher Sam Bond taking Sediment Elevation Table (SET) measurements in the marsh

Researcher Sam Bond taking Sediment Elevation Table (SET) measurements in the marsh

When exploring the marsh, Anne, a scientist at the Plum Island Ecosystems Long Term Ecological Research site, noticed that the salt marsh appeared to be changing over time. One species of plant, salt marsh cordgrass (Spartina alterniflora), appeared to be increasing in some areas. At the same time, some areas with another species of plant, salt marsh hay (Spartina patens), appeared to be dying back. Each of these species of plants is growing in the soil on the marsh floor and needs to keep its leaves above the surface of the water. As sea levels rise, the elevation of the marsh soil must rise as well so the plants have ground high enough to keep them above sea level. Basically, it is like a race between the marsh floor and sea level to see who can stay on top!

Anne and her colleges measured how fast marsh soil elevation was changing near both species of plants. They set up monitoring points in the marsh using a device called the Sediment Elevation Table (SET). SET is a pole set deep in the marsh that does not move or change in elevation. On top of this pole there is an arm with measuring rods that record the height of the marsh surface. The SETs were set up in 2 sites where there is salt marsh cordgrass and 2 sites where there is salt marsh hay. Anne has been taking these measurements for more than a decade. If the marsh surface is rising at the same rate as the sea, perhaps these marshes will continue to do well in the future.

Featured scientist: Anne Giblin from the Marine Biological Laboratory and the Plum Island Ecosystems Long-Term Ecological Research site

Flesch–Kincaid Reading Grade Level = 9.1

Does sea level rise harm Saltmarsh Sparrows?

Painting of the saltmarsh sparrow

Painting of the saltmarsh sparrow

The activities are as follows:

For the last 100 years, sea levels around the globe have increased dramatically. The cause of sea level rise has been investigated and debated. Data from around the world supports the hypothesis that increasing sea levels are a result of climate change caused by the burning of fossil fuels. As we warm the Earth, the oceans get warmer and polar ice caps melt. The dramatic increase in sea level that results could seriously threaten ecosystems and the land that humans have developed along the coast.

Salt marshes are plains of grass that grow along the east coast of the United States and many coasts worldwide. Salt marshes grow right at sea level and are therefore very sensitive to sea level rise. In Boston Harbor, Massachusetts, the NOAA (National Oceanic and Atmospheric Administration) Tide Gauge has measured a 21mm rise in sea level over the last 8 years. That means every year sea level has gone up an average of 2.6mm since 2008 – more than two and a half times faster than before we started burning fossil fuels! Because sea level is going up at such a fast rate, Robert, a scientist in Boston, became concerned for the local salt marsh habitats near his home. Robert was curious about what will happen to species that depend on Boston’s Plum Island Sound salt marshes when sea levels continue to rise.

Robert preparing his team for a morning of salt marsh bird surveys.

Robert preparing his team for a morning of salt marsh bird surveys.

Robert decided to look at species that are very sensitive to changes in the salt marsh. When these sensitive species are present, they indicate the marsh is healthy. When these species are no longer found in the salt marsh, there might be something wrong. The Saltmarsh Sparrow is one of the few bird species that builds its nests in the salt marsh, and is totally dependent on this habitat. Saltmarsh Sparrows rely completely on salt marshes for feeding and nesting, and therefore their numbers are expected to decline as sea levels rise and they lose nesting sites. Robert heard that scientists studying Connecticut marshes reported the nests of these sparrows have been flooded in recent years. He wanted to know if the sparrows in Massachusetts were also losing their nests because of high sea levels.

For the past two decades Robert has kept track of salt marsh breeding birds at Plum Island Sound. In his surveys since 2006, Robert counted the number of Saltmarsh Sparrows in a given area. He did these surveys in June when birds are most likely to be breeding. He used the “point count” method – standing at a center point he measured out a 100 meter circle around him. Then, for 10 minutes, he counted how many and what kinds of birds he saw or heard within and just outside the circle. Each year he set up six count circles and performed counts three times in June each year at each circle. Robert also used sea level data from Boston Harbor that he can relate to the data from his bird surveys. He predicted that sea levels would be rising in Plum Island Sound and Saltmarsh Sparrow populations would be falling over time.

Featured scientist: Robert Buchsbaum from Mass Audubon. Written by: Wendy Castagna, Daniel Gesin, Mike McCarthy, and Laura Johnson

Flesch–Kincaid Reading Grade Level = 9.5

Saltmarsh-Sparrow-104-crAdditional teacher resources related to this Data Nugget include:

coordinates

station locations

Lizards, Iguanas, and Snakes! Oh My!

The Common Side-blotched Lizard

The Common Side-blotched Lizard

The activities are as follows:

Throughout history people have settled mainly along rivers and streams. Easy access to water provides resources to support many people living in one area. In the United States today, people have settled along 70% of rivers.

Today, rivers are very different from what they were like before people settled near them. The land surrounding these rivers, called riparian habitats, has been transformed into land for farming, businesses, or housing for people. This urbanization has caused the loss of green spaces that provide valuable services, such as water filtration, species diversity, and a connection to nature for people living in cities. Today, people are trying to restore green spaces along the river to bring back these services. Restoration of disturbed riparian habitats will hopefully bring back native species and all the other benefits these habitats provide.

Scientist Mélanie searching for reptiles in the Central Arizona-Phoenix LTER.

Scientist Mélanie searching for reptiles in the Central Arizona-Phoenix LTER.

Scientists Heather and Mélanie are researchers with the Central Arizona-Phoenix Long-Term Ecological Research (CAP LTER) project. They want to know how restoration will affect animals living near rivers. They are particularly interested in reptiles, such as lizards. Reptiles play important roles in riparian habitats. Reptiles help energy flow and nutrient cycling. This means that if reptiles live in restored riparian habitats, they could increase the long-term health of those habitats. Reptiles can also offer clues about the condition of an ecosystem. Areas where reptiles are found are usually in better condition than areas where reptiles do not live.

Heather and Mélanie wanted to look at how disturbances in riparian habitats affected reptiles. They wanted to know if reptile abundance (number of individuals) and diversity (number of species) would be different in areas that were more developed. Some reptile species may be sensitive to urbanization, but if these habitats are restored their diversity and abundance might increase or return to pre-urbanization levels. The scientists collected data along the Salt River in Arizona. They had three sites: 1) a non-urban site, 2) an urban disturbed site, and 3) an urban rehabilitated site. They counted reptiles that they saw during a survey. At each site, they searched 21 plots that were 10 meters wide and 20 meters long. The sites were located along 7 transects, or paths measured out to collect data. Transects were laid out along the riparian habitat of the stream and there were 3 plots per transect. Each plot was surveyed 5 times. They searched for animals on the ground, under rocks, and in trees and shrubs.

Featured scientists: Heather Bateman and Mélanie Banville from Arizona State University. Written by Monica Elser from Arizona State University.

Meet the scientist! Click here to watch a video where scientist Heather explains her research!

Flesch–Kincaid Reading Grade Level = 9.8

Can a salt marsh recover after restoration?

Students collecting salinity data at a transect point. The tall tan grass is Phragmites.

Students collecting salinity data at a transect point. The tall tan grass is Phragmites.

The activities are as follows:

In the 1990s, it was clear that the Saratoga Creek Salt Marsh in Rockport, MA was in trouble. The invasive plant, Phragmites australis, covered large areas of the marsh. The thick patches of Phragmites crowded out native plants and reduced the number of animals, especially migrating birds, because it was too thick to land in. Salt marshes are wetland habitats near ocean coasts that have mostly water-loving, salt-tolerant grasses. Human activity was having a huge effect on the health of the Saratoga Creek Salt Marsh by lowering the salinity, or salt concentrations in the water. Drains built by humans to keep water from rainstorms off the roads changed how water moved through the marsh. The storm drains added a lot of runoff, or freshwater and sediments from the surrounding land, into the marsh after rainstorms. Adding more freshwater to the marsh lowers salinity. The extra sediment that washed into the marsh raised soil levels along the road. If the soil levels get too high, the salty ocean water does not make it into the marsh during high tide. Perhaps these storm drains were changing the salinity of the marshes in a way that helped Phragmites because it grows best when salinity levels are low.

In 1998, scientists, including members of the Rockport Conservation Commission and students from the Rockport Middle School science club, began to look at the problem. They wanted to look at whether freshwater runoff from storm drains may be the reason Phragmites was taking over the marsh. They were curious whether the salinity would increase if they made the storm water drain away from the marsh. They also thought this would stop the runoff sediments from raising soil levels. If so, this could be one way to restore the health of the salt marsh and reduce the amount of Phragmites.

In 1999, a ditch was dug alongside the road to collect runoff from storm drains before it could enter the marsh. A layer of sediment was also removed from the marsh so ocean water could reach the marsh once again. Students set up transects, specific areas chosen to observe and record data. Then they measured the growth and abundances of Phragmites found in these transects. They also measured water salinity levels. Transects were 25 meters long and data were collected every meter. The students decided to compare Phragmites data from before 1999 and after 1999 to see if diverting the water away from the marsh made a difference. They predicted that the number and height of Phragmites in the marsh would go down after freshwater runoff was reduced after restoration.

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View of Saratoga Creek Salt Marsh several years after restoration, showing location of one of the transects. Native grasses are growing in the foreground.

View of Saratoga Creek Salt Marsh several years after restoration, showing location of one of the transects. Native grasses are growing in the foreground.

Featured scientists: Liz Duff from Mass Audubon, Eric Hutchins from NOAA, and Bob Allia and 7th graders from Rockport Middle School

Written by: Bob Allia, Cindy Richmond, and Dave Young

Flesch–Kincaid Reading Grade Level = 9.5

For more information on this project, including datasets and more scientific background, check out their website: Salt Marsh Science

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

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