Changing Seas

Along scenic coastlines in the South, waves of mesmerizing green and golden grass stretch to the horizon.

This is the salt marsh - part liquid, part solid, an ever-shifting landscape stretching for miles before it meets the sea.

Coastal marshes are found anywhere there's soft sediment and not too much wave action.

In the U.S. our big marshes are in South Carolina and Georgia, and then areas like Louisiana.

There's a huge amount of life that lives here.

Marshes function as nursery grounds for a number of commercially and recreationally important species.

Everything from shrimp to crab to fish that are very popular with sportsmen.

Between the ebb and flow of the tides, the only constant is change.

Fish will move onto the marsh at high tide to feed.

And at low tide, you'll get more terrestrial organisms.

Herons and egrets and ibis, spoonbills all of them feed in the marsh.

And organisms that are in the mud come out like the crabs.

So it's really fluid.

Marshes filter nutrients and contaminants from the water and serve as buffers during storm.

They provide protection from wave energy, from hurricanes.

It is an absolutely beautiful landscape.

I mean I love everything including the smell of a healthy salt marsh on a moist morning.

They really give a sense of place to Georgians, South Carolinians, North Carolinians and Floridians.

As we're worried about climate change, marshes are one of the important habitats that can help take up carbon and store it rather than have it be in the atmosphere.

How do scientists study the salt marsh?

And how resilient is it to climate change?

Major funding for this program was provided by The Batchelor Foundation, encouraging people to preserve and protect America's underwater resources.

Additional funding was provided in loving memory of David G. Perrot, by the Perrot Family Endowment for Environmental Education.

The southeast coast of the United States is famous for its extensive salt marshes.

In coastal Georgia, moss-draped live oaks give way to vast expanses of grass, broken up only by winding creeks.

We have a very beautiful wild coastline.

I think the people in this state really appreciate the marshes and it is part of the identity.

We have about 350-thousand acres of salt marsh here on the coast of Georgia, which is about a third of what you have on the East coast today.

We only have 110 miles of coast, but I heard once that if we measured all the tidal creeks, we have about 5,000 miles of shoreline in this marsh habitat.

Georgia has several factors that give us so much marshland and one of them is the tidal range.

And that is due to the shape of the coastline and the gradual slope of the continental shelf.

Our average tide is about seven feet.

And it can be higher entering some parts of the year.

So that's a pretty big shift from high tide to low tide.

Most of Georgia s 14 barrier islands remain largely undeveloped and wild, including Sapelo Island about an hour south of Savannah.

It is home to the University of Georgia s Marine Institute.

There's a long history of salt marsh research here at the University of Georgia Marine Institute, and it dates back to the middle of the last century when a number of famous ecologists started working on the Georgia salt marshes.

And so there's just an enormous amount of knowledge that's been gained over the years that really makes this location the premier place in the world to study salt marshes.

We really are standing on the shoulders of giants.

And the cutting edge-research continues.

Dr. Merryl Alber leads the Georgia Coastal Ecosystems Longterm Ecological Research Project, which currently involves 22 scientists from ten different universities.

We ve been studying the marsh here since 2000.

The overall underlying theme is from an ecological perspective, understanding long-term change.

One key component of the project is the annual fall monitoring.

That shows us what's happening over decadal scales in the system.

We do that in the fall because that's the end of the growing season.

We have a network of 10 sites, and so the idea is to assess the functioning of the marsh from year to year.

And we've been doing that now for 21 years and we're starting to see interesting patterns of what affects the plant productivity in particular.

Along the Southeast coast and into the Gulf of Mexico, Spartina alterniflora, commonly known as smooth cord grass, is the dominant grass species found in tidal salt marshes.

The biggest thing that drives how vigorous the plants are is how much fresh water is coming down the rivers.

And what that freshwater does is it makes the marshes a little less salty.

Even though these are salt marsh plants, they still have to deal with salt being a physical stress to them.

And so a little less salt means they can grow a little bit better.

And we see two-to-three-fold differences from one year to the next and how much biomass there is at the end of the year.

Another thing that affects the productivity of the marsh plants is temperature.

So in hot years, the plants don't grow as well.

And that of course is a concern when we think about climate change.

The scientists also count the number of invertebrates found in the marsh There's the Periwinkle snail and that feeds on fungus that is decomposing the marsh plants.

In doing so if, if there's a lot of snails, they'll damage the plants as well.

And so when the snails are really abundant, they can suppress the biomass of the plants.

A second common invertebrate is fiddler crabs, and they are what we would call an engineer because they dig burrows, which improve the nutrients, getting into the soil.

And so they stimulate plant growth.

The third invertebrate is the Marsh mussel, and they filter the water and deposit sediment, and waste products onto the marsh surface.

And so they're building marsh elevation, and also fertilizing the plants.

Starting in the late 1950s salt marsh ecologist Dr. John Teal was the first to study the productivity of the marshes surrounding Sapelo Island.

He wanted to know where all the carbon entering the marsh ends up.

Carbon is one of the key building blocks of life, which cycles through the living and non-living parts of the environment.

We can think about how much the plants grow and how much energy is going into that plant growth.

And then how much production went into the various organisms that might use it in the marsh.

How much of it goes into the atmosphere, how much of it goes out with the water and then fuels the coastal ocean.

More than 60 years later, scientists are still investigating the answers to these same questions.

Since 2014 high tech instruments are helping to track the movement of carbon in the salt marsh.

This is the flux tower and we are actually collecting every five minutes 88 different environmental variables from 21 different instruments.

And in addition to that, with the carbon flux itself, we are collecting 16 variables at a much higher frequency of ten times a second, which adds up to 864 thousand measurements a day of just CO2 flux data.

In particular, we're looking at carbon dioxide.

So we're looking at carbon exchange between the marsh and the atmosphere.

Research has shown that coastal wetlands such as salt marshes, mangroves, and seagrass beds can bury carbon at a rate that s 10-100 times higher than upland forests.

And that's a very active area of research trying to understand how much carbon can we bury, how long will it be buried for?

And is this a way that we can try to decrease CO2 levels in the atmosphere, which are leading to warming trends right now.

To better track the fate of the carbon, the researchers are looking at the above and below ground biomass of the plants, by taking monthly cores of short, medium, and tall spartina found in different areas of the marsh.

The plants grow taller as we get down closer to the water.

Once back at the lab, the scientists wash the mud off the plants.

Different sections of the organic material are then put in a drying oven and weighed, to determine the biomass contained in each sample.

We are very interested in the differences between the forms of spartina, the tall, versus medium versus short, because there are differences in the amount of below ground material, even though the tall plants are very tall on the surface, there is actually less below ground material associated with them then the shorter forms.

So we have habitat map of the whole area and we know where the tall plants are found and the medium and the short so we can extrapolate that to get information on the biomass pattern through the whole system.

And then, we can use remote sensing and satellite work and we are able to then look at the change in below ground biomass based on the above ground characteristics.

We've seen some evidence that we're losing some of that below ground, which is worrisome.

We're concerned what that might mean for the plants to thrive, but also for the plant's ability to hold that sediment in place.

The scientists think the loss of below ground biomass might be caused by an increase in sea-levels.

How well salt marshes fare as sea levels rise is partly determined by how much sediment is building up on the marsh.

Until recently Georgia s marshes were thought to be relatively robust, especially compared to marshes elsewhere in the United States.

From the work that we've done over the last 20 years here along the Georgia coast, we find that marsh accretion rates are somewhere between a millimeter to perhaps three millimeters per year.

The average rate of sea level rise over the last 80 years is about three and a half millimeters per year.

And so in general, we find that the marshes are not keeping up with the rate of sea level rise.

Luckily our marshes have something called elevation capital, which means that they sit a little bit higher in the tidal frame.

And so they have a ways to go before they start drowning.

But at current rates of sea level rise, it doesn't appear that the marshes are keeping up.

The models that predict sea level rise say that by the year 2100, we will start to then see a rapid loss in the Georgia salt marshes.

The future impacts of sea level rise not only pose a threat to the marsh itself, but also to the humans living on its edge.

This is particularly true on barrier islands, like the popular tourist destination Tybee Island, near Savannah.

Living on a barrier Island, you have the ocean on one side and you have the extensive back barrier environment which is typically filled with salt marsh on the backside.

On the front side, we know how to protect ourselves from storms.

And we know that we need to build large sets of sand dunes, which serve as sacrificial erosional features that protect our upland infrastructure.

On the back side of the island, the answer to storm flooding is not quite so clear.

The salt marsh extends right up to the upland and there are many houses that are built near the edge of the marsh.

So it is not obvious how you would build some kind of feature to stop back barrier flooding.

Sedimentary Geologist Dr. Clark Alexander, together with other scientists from the University of Georgia, is working with the city of Tybee to figure out potential solutions to protect the backside of the island from flooding in the future.

The city of Tybee Island has been very proactive.

They retro-fitted a number of their storm drain systems.

So when storm tides were high, water didn't come up the storm drain system and flood the uplands.

They've looked at building a wall around the backside of the island, but it's actually not financially possible.

Tighten up that nut as tight as you can.

To determine how much sediment is accumulating in the marsh behind the island, scientists take a foot and a half long section of the mud.

And then we're going to take it back to the lab.

We're going to slice it up into thin sections vertically.

By looking at the half lives of naturally occurring radionuclides in those sections, the scientists can determine how much and at what rate sediment has accumulated over the last 100 years or so.

And that will give us some idea of how these marshes are keeping up with current rates of sea level rise.

Salt marshes also occur along the northern portions of Florida s Gulf coast.

Scientists with the state s Fish and Wildlife Research Institute s Garcon Point Lab near Pensacola study a variety of fishes that spend time in the marsh.

The tiniest is the Saltmarsh topminnow, which is thought to be rare and declining in numbers.

Salt marsh topminnows inhabit tidal marshes along the Gulf of Mexico, from Texas to Florida.

And in Florida, they only occur in the Northwestern portion of the state.

Chelsea Miles-McBurney has spent the last five years monitoring 32 randomly selected sites in the marsh, to figure out where these fish live, what sort of habitat they prefer, and if their population is stable.

The saltmarsh topminnow was listed as threatened by the state of Florida in 1977, due to its restricted range, diminishing habitat and population fragmentation.

This species is actually currently considered a federal candidate for listing by the U.S.

Fish and Wildlife Service.

To catch the tiny minnows, experts use two different types of traps.

And we set those in a 12 by 16-meter grid, alternating trap type.

So we set those in the afternoon and we'll pick them up in the morning and all fish that are in the trap get identified, tallied and released.

And for all salt marsh top minnows that we come in contact with, we will take the total length, record the reproduction status, we also record a lot of habitat parameters, including the type of vegetation around the trap.

Saltmarsh topminnows prefer typically low to moderate salinity levels, so that true brackish environment, and they can typically be found along the edges of marshes or within those intertidal creeks that are within the marsh.

Experts also take small fin clips for DNA analysis.

This research has shown there are five genetically distinct groups of saltmarsh topminnows in Pensacola Bay.

And while the overall population appears to be stable, future research is needed to identify specific threats to each of these subgroups and the potential risk of extinction.

Another fish that spends time in some of Florida s salt marshes is the rather large and prehistoric looking alligator gar.

Primarily they're freshwater fish species, but we're finding out they have fairly high tolerances for salinity.

And so they can move in between fresh and brackish and even full strength saltwater fairly easily.

Alligator Gar occur west of the Apalachicola River here in Florida.

And that extends on into Texas and down South into Mexico.

And then as far North as Illinois.

In 2006 the Florida Fish and Wildlife Conservation Commission closed the harvest of alligator gar in state waters.

There was some concern that alligator gar populations in Florida were going down and they wanted to step in and do something before it was too late.

Since 2010 the Garcon Point Lab scientists have been conducting research in Pensacola Bay and its tributaries to get an idea of how many alligator gar are found there.

Around 2015 we were able to estimate there were about 212 alligator gar in the Escambia river.

From there, we decided to take what we had learned on the Escambia River and apply it to other rivers.

To catch the fish the scientists set large-mesh gillnets.

Once an alligator gar is caught, the experts collect a variety of data.

Alligator gar are able to breathe air and are fine out of the water so long as they are kept moist.

There are several species of Gar here in Florida and at first glance, they all look similar.

But there are some major differences between them namely the size of the fish.

Alligator gar can weigh over 300 pounds and grow up to eight feet in length.

Back in the 50s and the 50s and even into the 70s, they were eradicated because they thought they consumed sport fish and we're finding out that's not the case.

To track the apex predator s movements, the scientists implant an acoustic tag into the fish.

This tag gives off unique pings that can be picked up by more than 70 acoustic receivers located throughout the bay.

That's like a computer that will pick up a tagged fish that swims by it.

Those things are picking up information 24 hours a day, 365 days a year.

The fish that we have tagged now in Pensacola Bay spend anywhere from six to eight months in the brackish water habitats, and then those other three to four months in the freshwater habitats during the spring.

Once the scientists have enough alligator gar tagged from across Pensacola Bay, they plan to do a population estimate for the entire watershed and determine which river the animals use to spawn.

The acoustic receivers scattered throughout Pensacola Bay are also used by Garcon Point Lab scientists studying Gulf sturgeon.

They have changed very little over the span of millions of years.

Essentially they are a swimming dinosaur.

Gulf sturgeon generally range eastward from the Suwanee river in Florida over to the Pearl river in Louisiana.

Once coveted for their meat and caviar, the Gulf sturgeon population has declined dramatically and has been listed as federally threatened since 1991.

What we're not seeing is an expansion as you would expect 35 years post listing.

And so that's what actually has guided our research.

Adult sturgeon appeared to be fairly stable.

We think that there's some sort of population bottleneck in the early life history stages of sturgeon, what we're referring to as generally the zero, one and two age group.

The scientists are part of a larger research team involving multiple partners studying juvenile gulf sturgeon across their range.

In the spring, the fish move into freshwater to spawn.

They remain there until late fall.

And they may fast for anywhere from six to eight months in these freshwater habitats.

Tagging data has shown where the sturgeon go once they leave freshwater.

Essentially the adult sturgeon will out migrate very quickly and they will move beyond the salt marshes to either sound habitats or even offshore habitats.

What we ve observed with juveniles specifically in the age, one, two and three range, is that they have an affinity for low salinity habitats, just outside the river mouth.

They exclusively occupy saltmarsh habitats.

Researchers say they hope to learn more about the survival rates of the juvenile fish.

And if survival for these early cohorts is particularly low, then that allows us to sort of hone in from a management perspective on, we need to really determine what's going on in these estuarine and these salt marsh habitats, because that appears to be one of the limiting factors to recovery of the population.

America s southern salt marshes are highly productive ecosystems linking the land and the sea.

And they re also a place of timeless beauty.

It's a real wilderness.

Just being in this beautiful, peaceful place I think is good for the soul.

It's hard to put a value on it.