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Diving Deeper: Episode 7 (Apr. 22, 2009) —
What is an Estuary?

HOST: Welcome to Diving Deeper where we interview National Ocean Service scientists on the ocean topics and information that are important to you! I’m your host Kate Nielsen.

Today’s question is….What is an estuary?

An estuary is a partially enclosed body of water such as bays, lagoons, or sounds, where rivers meet the sea. An estuary begins where fresh river water flows into coastal bays and inlets. These areas of transition between the land and the sea are driven by tides, but sheltered from the full force of ocean wind and waves. When freshwater meets salty seawater the result is a brackish mixture.

To help us dive a little deeper into this question, we will talk with Sarah McGuire and Bart Merrick on estuaries – what they are, why we study them, and why they are important to us. Sarah is the Education Coordinator with the Chesapeake Bay Virginia National Estuarine Research Reserve and Bart is the Education Coordinator with the Chesapeake Bay Maryland National Estuarine Research Reserve. Hi, Sarah and Bart, welcome to our show.

SARAH MCGUIRE: Hi Kate, thanks for having us.

BART MERRICK: Hi Kate, thank you as well and I’m looking forward to talking to you a little bit more about estuaries.

HOST: Great. Sarah, first, where are estuaries located?

SARAH MCGUIRE: Well, estuaries can be found all over the world. As you said, estuaries are typically where freshwater and saltwater mix together such as a bay or a lagoon. In the United States they’re found all across the board. And, usually you find larger cities are located near estuaries. For example, New York City is located on an estuary and that’s just because historically major cities were built where the mouth of a river would be. The largest estuary in North America is actually right here in the Chesapeake Bay. 

HOST: Sarah, what type of plants and animals live in estuary?

SARAH MCGUIRE: Well that’s a good question because estuaries are one of the most productive ecosystems in the world, so there’s a great diversity of animals that live there and plants. Estuaries can have many different types of habitats. Some of the examples would be oyster reefs, coral reefs, rocky shores, submerged aquatic vegetation, marshes, mangroves, and many other types. So in an estuary, there are different animals that live in each habitat. Some of those animals and plants could include fish, shellfish, and migratory birds. For example in the Chesapeake Bay, we have different habitats such as oyster reefs and in oyster reefs we might see oysters and mud crabs and small fish that live in between the shells. We have submerged aquatic vegetation where we find seahorses and blue crabs and lots of other fish. And then we also have open water and we might even see sea turtles or rays in that water. And different animals live in the estuary during different times of the year. One of the reasons for this variability is because the systems are tidally driven.

HOST: Bart, Sarah mentioned a little bit about change or variability in estuaries. Can you expand on this for us?

BART MERRICK: The fact that they’re tidally driven is really important as a physical parameter that the water levels are going up and down a couple times a day. In addition to that though, there’s also a lot of other chemical and physical parameters that change a lot within estuaries. We talk about it in terms of variability, which just means that things are going all over the map. And when I say things, I’m actually talking about different properties of the water like water chemistry, the temperature, the pH, salinity, things along those lines. And when you think about it, all the things that live in an estuary, they need to be able to deal with that variability. So, if you’re an oyster, you need to be able to handle oxygen levels that are pretty high and ones that get pretty low because you can’t move. If you’re a fish, you could get out of there if you wanted to.

HOST: Bart, can you tell us why are estuaries important?

BART MERRICK: They’re important for all kinds of reasons. Some of the biggest reasons why estuaries are important is that, like Sarah mentioned, most of the population of the world actually lives right on the edge of an estuary. And so, whether you’re getting your food from estuaries or you’re getting recreational benefit from estuaries, it’s all there. Some of the things particularly for me that I’m concerned about and why I think estuaries are important are that they provide very vital nesting and feeding habitats for tons of aquatic plants and animals. Some of the animals, like I mentioned earlier oysters, make estuaries their permanent home. And others like rockfish or horseshoe crabs or really birds will migrate through and they’ll stop over for either spawning reasons or feeding reasons.

So, estuaries also, and this is particularly important, they actually help maintain a pretty healthy ocean. They’re like the pre-treatment for our oceans. And so, as the water flows out of the watersheds around estuaries, it flows through wetlands through the actual estuary itself and a lot of times that will filter out a lot of the pollutants or contaminants that might be within the water and it filters it all out before it gets to the ocean.

HOST: Sounds like there’s a lot of environmental benefits to estuaries. Bart, can we assess the importance of estuaries economically as well?

BART MERRICK: Estuaries are often economic centers of coastal communities because they provide for almost 75 percent of U.S. commercial fish catch and even a greater percentage of the recreational fish catch. The total fish catch in estuaries contributes about $4.3 billion a year to the U.S. economy. And, estuaries are also important recreational areas. Millions of people visit estuaries each year to boat, to swim, to watch birds, canoe, kayak, and in fact, nature-based tourism is actually one of the fastest growing segments of the tourism industry.

Additionally, estuaries are also important centers for transportation. So that iPod you might be listening to this on, was probably on a boat that came into an estuary. And that’s a big part of the estuarine equation is the fact that they’re centers of transportation – they’re great places to move cargo.

HOST: Sarah, I was going to ask why we study estuaries, but with all of these examples of benefits that estuaries provide – both environmentally and economically, I guess it’s pretty clear why we study these.

SARAH MCGUIRE: Right. We study estuaries for all of the reasons that Bart just mentioned. They’re important to our economy, there are many species that depend on estuaries, and we need to know the balance to protect those areas. When we study estuaries, we can figure out what impact human actions have on these ecosystems and we can help manage the land surrounding estuaries in order to protect them.

HOST: Sarah, how are estuaries important to those who don’t live along the coast?

SARAH MCGUIRE: That’s a good question. Bart actually mentioned the watershed a little bit and even if you don’t live along the coast, there are six states that flow into just the Chesapeake Bay watershed, and a lot of those areas are not right along the coast. So, no matter where you live, eventually you can impact an estuary because your water will flow into a river that will eventually flow into an estuary. That’s one reason why estuaries are important no matter where you live.

Also, estuaries are used as recreation areas as Bart mentioned and people vacation often times near estuaries. Estuaries are nurseries for many fish so they are also important to the seafood industry. So no matter where you live, you can connect to an estuary.

HOST: Bart, what is the role of the National Ocean Service in studying and protecting our nation’s estuaries?

BART MERRICK: The National Ocean Service is home to the Office of Ocean and Coastal Resource Management and they basically oversee the National Estuarine Research Reserve System that Sarah and I both work with. The key thing here is that it’s also the NOAA group that we just described there and the state partners that manage the estuarine reserves. So, the Reserve System was created by the Coastal Zone Management Act in 1972 and the Reserve System is a national network of coastal reserves established as living laboratories for long-term research and education. These reserves monitor the health of estuaries, educate the public about these ecosystems, and help communities manage their coastal resources better.
HOST: Bart, this is great that there’s such an extensive network that exists for these purposes – for research and education. How many reserves are there?

BART MERRICK: There are currently 27 reserves in 21 states and Puerto Rico. The reserves are located around the coastal United States and even one site in the Great Lakes which is actually Old Woman Creek. As I mentioned before, the reserves is a partnership between NOAA and the coastal states and the partnership protects more than 1.3 million acres of estuarine land and water.

HOST: For both of you actually, maybe Sarah first. Since reserves were established as living laboratories to conduct scientific research, can you elaborate a little bit more on the research that’s happening right now at your reserve?

SARAH MCGUIRE: One example of research happening in the Chesapeake Bay Virginia Reserve, and all of the reserves actually, is the System-wide Monitoring Program, which is a series of fixed water-quality stations that each reserve has and these stations provide long-term data sets. Each station monitors physical parameters of the water and each reserve is responsible for collecting this data. The long-term data sets are important because they can show long-term changes in the water.

BART MERRICK: One of my favorite, sort of specific, research programs that we have going on in the Chesapeake Maryland, and I think Chesapeake Virginia’s doing it too, Reserve is we have these studies set up that measure the amount of sediment that comes into a marsh. And that’s super important because one of the concerns of the Reserve System is related to climate change. One of the impacts of climate change is sea level rise and these marshes that exist within estuaries are very important for all of the reasons we’ve talked about before, but they are right there on the edge of the water. And if the water level creeps up a little bit, the marshes are going to change. So, in the marshes around the bay, we actually have these things called sediment elevation tables and they measure – very, very accurately – how much sediment is building up on the marshes. And then we can use that information to determine whether or not the marsh is keeping up with the sea level rise.

HOST: It’s great that data from so many of these local reserve research efforts are available for the public. Bart, are there examples of how research conducted at the reserves supports local decision making and local efforts?

BART MERRICK: Yeah, there’s a number of examples. One of my favorite examples to share with folks is within the Chesapeake Bay Reserve there’s a place called Jug Bay, which is one of our sites on the Patuxent River. On this river, there’s an area in Jug Bay that supports a plant, that’s actually a pretty important plant that’s called wild rice. Wild rice was disappearing for awhile and they were trying to figure out why. It’s important basically as food for migrating birds or birds that are living there. The question is why is it disappearing and then what can we do to bring the wild rice back. And through some of the research happening at the reserve we found that there’s a whole bunch of reasons – sea level rise one of them, goose predation another one, actually resident geese eating it is the big problem. So, basically, we developed then a strategy for maintaining the rice and preventing goose predation, which involved fencing off the wild rice which would prevent the geese from landing in there. And that actually has led to a pretty successful rebound in the amount of wild rice in Jug Bay. And this type of effort, just simple fencing around stands of wild rice or where we hoped wild rice was or where we planted wild rice, has done a lot to actually bring the amount of wild rice for those migrating water fowl that come from the entire Eastern seaboard through the Chesapeake Bay.

HOST: Thanks for that great example for Jug Bay and showing us a little bit more about how that research is used locally to solve different problems. Sarah, are reserves similar to marine protected areas in that they are protected areas that restrict activities to benefit local conservation efforts?

SARAH MCGUIRE: The reserves are similar to marine protected areas. They are composed of different sites that are managed by that reserve in order to protect the land and the area around it. It’s kind of hard to say for each reserve because they’re so different, but, each reserve would have their own set of guidelines and restrictions and the best thing to do would be to check with your local reserve to see what guidelines they have. Some of the activities that might be limited would be fishing and hunting or camping. It just depends on the site.

HOST: Thanks. It does sound like each reserve is different. There’s something a little special that happens at each site. Bart, how many staff are needed to run or maintain the reserve sites?

BART: That varies across the board. Some reserves have 20 people, some reserves have five people, but each reserve does have five core positions. And those are the Education Coordinator, which Sarah and I both are, in charge of working with the general public as well as students in the kindergarten up through graduate school. Then there’s the Research Coordinator who’s in charge of all the research that’s going on within the reserve. And then the Coastal Training Program Coordinator, that’s actually a great position, and that person is in charge of taking the research that we get at the reserves and communicating that research to decision makers to try to help them make more informed decisions that might impact the estuaries. The Stewardship Coordinator is responsible for a lot of the restoration efforts and acquiring land to add to the reserve or to put into an easement or something along those lines. And then there’s of course the Manager that really brings it all together. And they’re responsible for making sure the research, the education, the stewardship, the coastal training programs are all well integrated and that we’re all using each other’s resources to get the message out about estuaries as effectively as possible.

HOST: Sounds like a big team effort to be able to maintain these sites. Sarah, can you tell us what a typical day is like for you as an Education Coordinator at the Virginia Chesapeake Bay Reserve?

SARAH MCGUIRE: Sure. As Bart said, there are five core positions at each reserve. So, a typical day for me might be hosting a school group that might come in in the morning. We’ll go out in the river and sample, see what animals live in that habitat, we might go back in the lab and use the microscopes and study oyster reef animals in the afternoon. It could entail a canoe trip for a school group or hosting teachers to teach them about our curriculum. But mostly, it’s just teaching the public, especially students, about estuaries and getting them excited about estuaries.

HOST: Great, thanks to you both for all of this valuable information and really good examples to help paint a little bit of a better picture about estuaries for us. It’s wonderful to hear more about these estuarine reserves that were established to help us learn more about research locally and just about estuaries. Do you have any final closing words for our listeners on estuaries or the Reserve System as a whole?

BART MERRICK: The biggest thing I would like to say is go to an estuary. The reserves are all open to the public and you’re more than welcome, and we actually really encourage folks to come visit outside of organized groups – school groups or community programs. They’re great places to canoe or bird or really explore a lot of your other recreational opportunities. And, if people don’t go there, then they’re less connected to the reserves and so it’s really important to us to make sure that we facilitate people actually getting out in the reserves, in the estuaries.

HOST: Thanks Bart and Sarah for joining us on today’s episode of Diving Deeper and talking more about estuaries, why they are important, and the Reserve System. To learn more about estuaries, please visit

That’s all for this week’s show. Please tune in on May 6th for our next episode on marine sanctuaries.