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  Archived Posts From: 2020


Can I and Should I Build a Living Shoreline…

Written on: December 9th, 2020 in Living Shorelines

By Kenny Smith, Wetland Monitoring & Assessment Program

The Delaware Living Shorelines Committee members are often asked questions by landowners. Many of those questions relate to the suitability of their property for a living shorelines project. For example: is it possible to build a living shoreline on their property? Can a living shoreline protect their property from coastal erosion or create more beneficial habitat for wildlife?

The Site Evaluation Guidance Document

The Delaware Living Shoreline Committee has a smaller sub-committee, the Design and Engineering Sub-Committee, that decided to tackle these questions. They created a document that informs professionals and landowners about the feasibility of a living shoreline for a property. This document is called Site Evaluation for Living Shoreline Projects in Delaware. 

The Design and Engineering Sub-Committee consists of individuals from a wide variety of backgrounds, from government employees to private contractors, that are installing living shorelines in Delaware. This diverse group provided the necessary expertise to digest a lot of information into an easy-to-follow document. The guidance highlights important metrics to look at on a shoreline. The document is separated into a desktop analysis and a field visit portion. In total, there are 12 metrics to calculate during the desktop analysis and 5 additional metrics to collect during the field visit.

Metrics in the site evaluation document.

Site Evaluation: Desktop Analysis

The desktop analysis portion of site evaluation document explains important environmental parameters that must be calculated to determine the feasibility of a site for a living shoreline. You can calculate these parameters using desktop tools and resources. The list of parameters starts with descriptions of the site, shoreline problem, project goals, dimensions, and body of water. While these descriptor metrics are very basic, they are the basis for all future plans for the site.

Fetch calculation for a potential living shoreline design.

The next step is to collect metrics that will steer design plans and feed into calculating some of the more complex metrics. These metrics include shoreline orientation and shoreline change rate. They also include geomorphology of the site, such as upland, shore, and submerged areas. This information is important in classifying current conditions at the site and determining what kind of techniques would be suitable. You will then use the fetch (distance over which wind blows on the water surface to generate waves) and wind metrics to calculate wave climate. From there you can determine expected energy.

The tide metric will provide you with an idea of the range of water your site receives. It will also provide a working window once your project is designed. Delaware has the FEMA maps available online and they are another helpful resource to inform you about the suspected storm energy a site may receive.

Site Evaluation: Field Visit

Horseshoe crabs, bivalves, and endangered species like the red knot can all influence a living shoreline design.

Once you have completed the desktop metrics, it is time to visit your site. While it is always better to visit your site multiple times, it is possible to collect the information you need for this evaluation during one visit. While completing the field metrics, you should also be double-checking all of the data that you collected during the desktop analysis. This is an opportunity to fine-tune anything you may have missed or needs to be corrected. In addition, it is a good idea to take as many photographs as possible from various angles and zooms to capture the shoreline.

For site boundaries, you are looking for both physical and jurisdictional boundaries, while for land use/ land cover, you are looking at how the surrounding land is used and what kind of vegetation is present. There is also another metric to capture the geology of your site based on the field visit and fill in any holes from the geomorphology desktop metric. Once again, look in the upland, shore, and submerged areas for sediment types and any other pertinent information. Ecology of your site is split into biotic and abiotic features. Biotic features include plants and animals, whereas abiotic features include water quality, soil type, and sunlight.

 It is very important to create site sketches, as they are the best way to quickly assess the spatial relationships among existing features, slopes, and land cover. You should draw a plan view and a profile view to best capture this information for later use during a design. You should also take note of any surrounding healthy shorelines, as they may be a helpful reference for your future site design.

Example site plan sketch showing a bird’s eye view of a project site with a variety of features.

Putting It All Together

The information you collect in the site evaluation document will help you determine current condition of shoreline. It will also help you figure out the most suitable living shoreline techniques, potential design constraints, and permitting conditions for your site.  For instance, your shoreline could be suitable for a planting and coir log design. On the other hand, it could need more protection and need to rely on a sill designed with rock to slow the energy down.

While this document can provide very vital information, it is important that you still consult a professional to create a design based off the information collected in the document. Sites with exposure to extremely high wave energy tend to present challenges when designing a living shoreline. Sites with steep shorelines or very shaded shorelines tend to present challenges as well.

Get Experience!

The Design and Engineering Sub-Committee usually hosts a one-day training for roughly 15 participants during the spring months going over the site evaluation guidance and then visiting 4-5 sites to use the information you gained on evaluating sites for living shorelines. Stay tuned for information on this training.

You can find the site evaluation document here. You can also find many other resources on the Delaware Living Shorelines Committee website.

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Beneficial Reuse of Dredge Material: Rebuilding a Former Tidal Wetland

Written on: December 9th, 2020 in Beneficial UseWetland Restorations

By Erin Dorset, Wetland Monitoring & Assessment Program

The Mid-Atlantic is a sea-level rise hotspot, meaning that rates of sea level rise in the region are relatively high. As such, scientists, outdoor enthusiasts, and coastal communities alike are all worried about the fate of tidal wetlands. Here at Delaware’s WMAP, we’re seeing what we can do to lend tidal wetlands a helping hand.

View looking out at the site of a new beneficial use project in Millsboro, DE. The area used to be a salt marsh and has been lost over the years, likely because of erosion and sea level rise.

Back in 2013, we worked closely with DNREC’s Shoreline and Waterway Management Section (SWMS) to apply a thin layer of dredge material to a struggling marsh at Piney Point along Pepper Creek. We have since monitored the site every year until 2019. Elevation sufficiently increased from the sediment application such that we saw plant life rebound and thrive in the years after. Seeing how successful the Piney Point project was, we were eager to try another similar project in Delaware.

An exciting new opportunity

In 2019, we identified a candidate project site along the Indian River in Millsboro. We saw in aerial imagery that what used to be coastal forest and tidal wetland has since eroded and retreated. Now, there is an intertidal mudflat that is completely devoid of plant life. The remaining marsh is likely to continue retreating if we don’t help the marsh recover.

Shoreline erosion over time at the Millsboro beneficial use project site.

By rebuilding this former tidal wetland, we will be recreating important wildlife habitat and better protecting nearby public infrastructure from storms and rising seas. We will also be testing a new method of tidal wetland restoration in Delaware involving thick sediment application. Previously at Piney Point, we applied a much thinner sediment layer to an existing marsh. For this project, we will apply a thicker layer to recreate a marsh that has been lost. We will be learning important new lessons about tidal wetland restoration by using this different method.  

Designing for Success

To ensure the success of this beneficial use project, we have been working closely with DNREC’s SWMS every step of the way, just as with Piney Point. The SWMS dredges the Indian River annually to maintain the navigation channel. Usually, they place dredged sediment near the project area in what is called a confined disposal facility (CDF) in a nearby upland. The SWMS will divert dredged sediments to the mudflat for this project instead of to the CDF. We will use that sediment to rebuild the former marsh.

The road to project design

WMAP collecting mudflat elevation data at the project site.

We collected important baseline field data before applying any sediment in order to create an accurate design plan. Baseline data included current site elevation, water levels, and elevations where different plants in the area are growing.  

We used the water level data to accurately predict tides at the site, which is necessary for performing fieldwork. We were also able to determine mean high water (MHW) and mean low water (MLW) at our site, both of which are important to know for permitting and for planting.

Additionally, we were able to use plant elevation readings to figure out our target elevation to rebuild the marsh. Our goal is to encourage the growth of the low marsh plant, saltmarsh cordgrass (Spartina alterniflora), and discourage the growth of the invasive European reed (Phragmites australis). Therefore, we chose a target elevation that is optimal for saltmarsh cordgrass, but not for European reed. We then calculated approximately how much sediment we will need to achieve that target elevation by using the mudflat elevation data.

We plan to apply dredged sediments to the project site over 2 winters (winter 2020/2021, and winter 2021/2022) to account for the high sediment need. Once sediment application is complete, we will plant the site with native seeds to help it recover.

Recovery will likely take several years, after which we hope to have achieved the following goals:

  1. The site will have the proper elevation for saltmarsh cordgrass to grow, and for low marsh habitat to sustain itself in the face of sea level rise.
  2. The site will be largely covered with saltmarsh cordgrass and will not contain invasive European reed.
  3. The constructed 7-acre area will be maintained.
  4. The site will be used by native marsh wildlife.

How do we know if we’ve achieved our project goals?

As with any wetland restoration project, it’s important to monitor the area over time. Monitoring allows scientists to determine if project goals are being met. For our monitoring plan, we paired our project site with a ‘reference marsh’. The reference marsh is a nearby salt marsh that is in relatively good condition that will not receive sediment. The reference site will help us see if conditions at the project site eventually approach natural salt marsh conditions.

We have recently collected a variety of data at both the project and reference sites before any sediment has been applied. The fieldwork we performed at both sites to collect these data include marsh bird surveys and nekton (free-swimming organisms)  surveys. We also performed vegetation surveys, bearing capacity (marsh stability) surveys, and benthic infauna surveys. In addition, we installed several  sediment plates to test them as methods of measuring accretion and erosion at our project site. Finally, we established several permanent photo points at the project  site that will help us visually document changes over time.

WMAP collecting monitoring data. From left to right: performing nekton surveys; measuring sediment plates; performing bird surveys.

We will collect data in the same fashion after sediment is applied to the project site for several years. By comparing the project site and the reference marsh both before and after sediment application, we will better be able to attribute any changes we see to our wetland restoration methods  instead of to natural variability.

Stay tuned for more updates!

This project is being conducted in partnership with DNREC’s Shoreline and Waterway Management Section.  For more information or questions about this project, please contact Alison Rogerson at or 302-739-9939.

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Salt Marshes: Working Hard Without Pay

Written on: December 9th, 2020 in Wetland Assessments

Guest Student Writer: Sandra Demberger, M.S., recent graduate,
Villanova University

Boaters, kayakers, and bird watchers are drawn to salt marshes for their quiet beauty. Wildlife, ranging from great blue herons to tiny fiddler crabs, and marsh grasses rustling in the soothing breeze, all draw recreators to these coastal systems. But did you know, these seemingly tranquil systems are hard at work providing valuable ecosystem services?

A tidal wetland in the Delaware Estuary.

An ecosystem service is a natural process that contributes directly or indirectly to the well-being of the human population¹. Salt marshes provide many ecosystem services. Some of these services include coastal protection from storm events, water filtration, and nursery habitat for economically important fish species. Additionally, scientists increasingly recognize salt marshes for their role in removing carbon from the atmosphere and storing it long-term in their soils. That process is called carbon sequestration.

All these valuable services are provided by the marsh free of charge!

Why is Carbon Sequestration Important?

Carbon dioxide is a major contributor to global climate change because it functions as a greenhouse gas. Greenhouse gases trap heat in our atmosphere, much like a garden greenhouse does. Consequently, these gases warm up our planet at an unnatural pace. This process results in what is commonly referred to as global warming, and, in turn, global climate change (a shift in climate as a result of warmer temperatures). Unfortunately, all of us are releasing carbon dioxide into the atmosphere by doing daily activities like driving our cars and heating/cooling our homes.

While we humans are putting carbon dioxide into the atmosphere, salt marshes are working hard to remove it!

Carbon sequestration is a valuable ecosystem service, naturally removing carbon from the atmosphere and locking it away in plant material for generations. While many ecosystems can sequester carbon, salt marshes have proven to be the experts. Salt marshes can sequester carbon at rates 10 times higher than other terrestrial wetland systems². Less carbon in the atmosphere means less greenhouse gases, and, ultimately, reduced global warming.

How do Salt Marshes Sequester Carbon?

Beautiful tidal wetland in the Delaware Estuary.

Carbon sequestration is a cycle with three key components: plant material, suspended sediments (think mud and sand particles floating in the water), and very slow natural sea level rise. Here is the basic carbon sequestration cycle:

1. Salt marsh plants need sunlight, water, and carbon dioxide to grow. This process is called photosynthesis. The carbon absorbed during photosynthesis is stored in the plant matter.

2. Over time, marsh plants will die and their plant matter, still full of carbon, will build up on the marsh surface. While some of this plant material will be decomposed by microbes in the marsh, a portion will remain.

3. Twice a day the tidal waters will bring suspended sediments onto the marsh surface during high tide. The still living plants will slow tidal waters, allowing suspended sediments to settle out of the water column onto the marsh surface.

4. These suspended sediments will bury the plant material (from step 2) as well as the carbon stored within it, and elevate the marsh surface.

5. Slow, natural sea level rise allows the marsh to gain elevation at a pace that can keep up. This cycle has continued over millennia to form deep carbon deposits.

Over thousands of years, this cycle has formed carbon-rich deposits reaching six meters in depth³. The rates of salt marsh carbon sequestration may vary by region due to factors like the length of the plant growing season and the amount of suspended sediments deposited on the marsh surface. Regardless of the pace of carbon sequestration, salt marshes are worth protecting for this important ecosystem service.

Why Should I care about Carbon Sequestration?

It is often challenging to convince non-salt marsh lovers of the importance of these systems. To many, salt marshes are buggy and muddy areas with no real use. Defining ecosystem services–in particular, their monetary value–helps people understand their importance.

The Social Cost of Carbon

Therefore, some economists have dedicated their careers to estimating the monetary value of ecosystem services. They have developed the social cost of carbon as a way to measure the monetary value of carbon sequestration in salt marshes. The social cost of carbon is the sum of all the costs of one additional ton of carbon dioxide being emitted into the atmosphere. Some of these costs may include more severe storms and wildfires, which destroy communities and reduced agricultural yields straining our food supply. The exact value may vary due to different assumptions and uncertainties about the impacts of climate change in the future (click here for more information). 

Me doing fieldwork in a salt marsh in the Delaware Estuary.

My Master’s research was related to this idea of valuing ecosystem services of salt marshes. Specifically, I focused on carbon sequestration in the Delaware Estuary. I found that the Delaware Estuary sequesters over 306,000 Mg Carbon dioxide annually. In other words, the Delaware Estuary removes the equivalent of carbon dioxide emitted from 66,109 passenger cars in one year. But this is still hard to comprehend. So, let’s apply the social cost of carbon!

The Delaware Estuary prevents about $18.32 million in damages every year by sequestering carbon from the atmosphere (using a $ 59.83 social cost of carbon value). If salt marshes stopped sequestering carbon tomorrow, society could expect to endure over $18 million in damages per year. This is pretty impactful!

This basic monetary valuation, in this case just for a single ecosystem service, helps provide context to an otherwise complex natural process.

Protecting Our Marshes

Accelerated sea level rise is a serious threat the salt marshes. Marshes unable to gain elevation at a pace that keeps up will drown and erode away. That, in turn, would cause large carbon deposits to be released back into the environment, contributing, once again, to global climate change.

Living shorelines, beneficial reuse of dredge material, and other restoration projects are essential to protecting marshes, and the large amounts of carbon stored within them, from accelerated sea level rise. Valuing carbon sequestration and other ecosystem services may help land managers and practitioners gain funding and support for these types of conservation efforts. Additionally, understanding the value of carbon sequestration, and the many other ecosystem services, may help conservationists discourage the development of retail and housing on these valuable landscapes.

1. U.S. Environmental Protection Agency. 2009. Valuing the protection of ecological systems and services. A report of the EPA Science Advisory Board. EPA, Washington, D.C., USA.
2. Bridgham, Scott D., Patrick J. Megonigal, Jason Keller, Norman Bliss, and Carl Trettin. 2006. The carbon balance of North American wetlands. Wetlands. 26:889–916.[889:TCBONA]2.0.CO;2
3. Chmura, Gail L. 2013. What do we need to assess the sustainability of the tidal salt marsh carbon sink? Ocean and Coastal Management83: 25–31.

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Derelict Crab Pots in Delaware’s Recreational Blue Crab Fishery

Written on: December 9th, 2020 in Outreach

Guest Writer: Kate Fleming, Delaware Sea Grant

When crab pots* are lost or abandoned at sea, they remain in the water, free to continue to capture blue crabs as they are designed to do. They can also capture other animals like diamondback terrapin and summer flounder. Since derelict crab pots are not tended by anyone, the animals that become trapped inside will eventually die. As such, these forgotten pots can lead to continued and needless mortality in our ecosystem in a process called ghost fishing.

Gear loss and abandonment is fairly common in pot-based fisheries. That’s because pots are designed to be placed in the water and left alone for days at a time before being checked on. This comes with some inherent risk for accidental loss and sometimes obstacles can come up that hinder a timely return.

Here in Delaware, blue crabbing is an important commercial industry. It is also a popular recreational past-time that leads to the capture of over 1 million blue crabs each year. Could it be that we have ghost crab pots scattered across the bottom of Delaware’s Inland Bays, where only recreational crabbing takes place? Based on the work I have been doing with University of Delaware Professor, Dr. Art Trembanis, I can say with confidence that the answer is yes, yes we do.

Ghost Crab Pots in the Inland Bays

Grant Otto (graduate student in the Coastal Sediments, Hydrodynamics, and Engineering Lab) and Chris Petrone Delaware Sea Grant Extension Director) hand off a derelict crab pot (Evan Krape UD)

This shouldn’t be particularly surprising given the ubiquitous nature of this type of marine debris. However, the shallow murky waters of our Inland Bays offer an effective hiding place. Last winter** we used a commercial-grade side scan sonar to document over 560 derelict crab pots submerged beneath the surface of just under 250 acres of Rehoboth Bay. This represents some of the highest densities of derelict crab pots that have been estimated in Chesapeake Bay, which supports one of the largest blue crabbing fisheries in the nation. We followed our surveys up with a pilot removal effort. We recovered about 100 derelict crab pots in just a couple days. (Read more about our pilot removal project here!).

Today our project team has grown to include University of Delaware graduate student Jen Repp. It also includes Delaware Sea Grant’s Fisheries and Aquaculture Specialist, Dr. Ed Hale. Our sights are now set on Indian River Bay. Jen and Art are initiating side-scan sonar surveys any day now. Plus, I am in the thick of planning Derelict Crab Pot Round-Ups across three days this January and/or February 2021. The whims of the weather will determine the specific dates!

Compared to last year’s pilot project, we plan to quadruple our survey area. We will be removing 10 times the number of derelict crab pots over the next two years, aided by volunteers with boats that are willing to wield a grappling hook and help us on the water. We’ll be staging out of Holts Landing State Park and keeping our fingers crossed for flat calm seas and the balmiest of winter temperatures!

Volunteer with Us!

Interested in helping out? We are targeting volunteers that can bring and crew their own boats. Click here for more information and to register a team, or contact me at with any questions!
If you don’t have a boat but would still like to contribute, there are a couple other volunteer opportunities that will likely come up with this project:

– We will be giving a subset of our recovered pots to the Partnership for Delaware Estuary (PDE) to be repurposed in a living shoreline experiment. Following the removal, the Center for Inland Bays (CIB) will be coordinating volunteers to transport these pots to Wilmington, DE where PDE is located. Interested volunteers can contact CIB Volunteer Coordinator, Nivette Perez-Perez at

– I will likely be looking for volunteer assistance to refurbish any remaining crab pots this spring or summer so that they can be reused for education and outreach. If that sounds like fun (I think it does), please reach out ( and I’ll get you on my list.

Preventing Crab Pot Loss and Associated Impacts

One of the most common questions I get when I talk about derelict crab pots in Delaware’s recreational blue crab fishery is: Why? Why would a recreational crabber abandon their pots? Our work doesn’t actually focus on answering that question. But, I often like to point out that DNREC-Enforcement has an existing program to curb crab pot abandonment in our state. The program issues notices and then seizes pots that have not been tended within three days as is required in Delaware. They actually let me collect data through this program. It has been an outstanding opportunity to learn about recreational crab pot abandonment rates. I’ve also learned a lot about Turtle Bycatch Reduction Device (TBRD) compliance (a little more on TBRD’s below).

Accidental Crab Pot Loss

With that program in place, I prefer to ponder the issue of accidental pot loss. I suspect it is an important contributor to the presence of derelict crab pots in our Inland Bays. If gear is rigged with old, degrading line it can be more susceptible to breakage by rough weather or boat propellers. Likewise, buoys assembled from hollow materials are more likely to fill up with water and sink if punctured. We have recovered quite a few derelict crab pots that had bleach bottle and bumper “floats” still attached that were no longer doing their jobs.

These are accidents of course. But, I do think there are things that recreational crabbers and boaters can do to minimize the potential to lose a pot. These are things like:
-Use those white foam bullet floats in lieu of bleach bottles or bumpers
-Change out your lines each year 
-Use line that sinks 
-Keep your eye on the weather forecast before you set your pots
-Update your tending plan if it looks like a storm is coming or you have to go out of town 

Likewise, boaters should:
-Stay vigilant for buoys on the water 
-Wear polarized sunglasses to make spotting them a little easier 
-Slow down and give buoys plenty of berth to avoid a line strike. The pot lines can be hard to see and are often times longer than you think.

Minimizing Impacts

Scutes provide evidence of diamondback terrapin mortality inside derelict crab pots (Evan Krape, UD)

Then there are things you can do to minimize impacts in the event that a pot does go missing. The first is to simply remember that the limit for recreational crabbers in Delaware is two pots per person. We know that some amount of pot loss is unavoidable. Therefore, keeping the number of pots fished to the required limits can reduce the overall quantity that end up on the Missing in Action list.

In Delaware, crabbers are required to install Turtle Bycatch Reduction Devices on all funnel entrances of a recreational crab pot. They help keep diamondback terrapins from getting inside the pots, where they will eventually drown. For more information on TBRD’s, or Terrapin Excluder Devices as they are often called, check out DNREC’s TBRD Pamphlet.

Cull rings are not actually required in Delaware. However, they have been shown to allow sublegal crabs (crabs you wouldn’t be able to keep anyway) and other small organisms to escape. They are required in some of our neighboring states, so should be fairly easy to find if you want to go the extra mile. A juvenile blue crab will thank you.

Many Thanks

I want to wrap up by offering some acknowledgement and thanks to those that have helped us with our past and current projects. It truly takes a village.

Delaware Sea Grant provided the seed funding to get our initial side-scan sonar surveys going to confirm the prevalence of derelict crab pots in Rehoboth Bay. We received additional funding from the University of Delaware School of Marine Science and Policy. Subsequently, we have received funding from Delaware Coastal Programs and the NOAA Marine Debris Program.

Delaware Coastal Programs and several sections within the Delaware Division of Fish and Wildlife (Enforcement, Fisheries, and Wildlife) have provided support to this project. They have provided a boat and labor on clean-up days, permitting support, technical assistance, and more. Rehoboth Bay Marina allowed us to stage our removal at their private boat ramp. This was invaluable to being able to work in Bay Cove, behind Dewey Beach last year.

Dave Beebe with Rehoboth Bay Oyster Company and Rich King from Delaware joined us on the water and were a big help (that is how I discovered the magic of a trash pump!). We couldn’t have done this work without the many University of Delaware staff and students that joined us from Art’s CSHEL Lab, Delaware Sea Grant, and others that simply volunteered to help. Vince Capone with Black Laster Learning has provided a lot of help to Art’s lab in the processing of side-scan sonar data.

From left to right: Jose Dominguez, Joseph Kessler, Matthew Breece, Nate Nazdrowicz, Chris Hauser, Taylor Deemer, Art Trembanis, Justin Guider, Robert Roose, Kate Fleming, Mark Lundine, Bryanna Lisiewski, and Hunter Tipton. (Evan Krape, UD)

Looking Ahead

We are looking forward to this year’s efforts. We’ve already had so much support from partners that have helped out in recruiting or have expressed a willingness to join us with field operations. In addition to partners already mentioned, thank you to the Center for Inland Bays, the U.S. Environmental Protection Agency, Delaware Mobile Surf Fisherman Club, Ducks Unlimited, Partnership for Delaware Estuary, Delaware Cooperative Extension, The Nature Conservancy. Also, thank you to all the volunteers that have reached out to express interest in helping out this winter. We’re grateful for your support and looking forward to a successful Derelict Crab Pot Round-Up!

*Commercial or Chesapeake-style crab pots are often referred to as crab traps, though crab pots is also technically appropriate. I prefer to use the term crab pots to differentiate them from recreational crab traps that have collapsible sides and are incapable of ghost fishing.  

**Why do we work in the winter? Our work has to take place between December 1 and the end of February each year to coincide with the closed blue crab season. This ensures that the pots we find and remove are in fact derelict!


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New Delaware Wetland Maps Available

Written on: September 24th, 2020 in Wetland Assessments

by Alison Rogerson, Wetland Monitoring & Assessment Program

Map of Delaware’s wetlands based on 2017 imagery.

Measuring wetland health and function is a primary task for DNREC’s Wetland Monitoring and Assessment. We work on this every year, one watershed at a time. Tracking wetland acreage across the state is also vitally important to managing Delaware’s wetland. Updating statewide wetland maps is a lot of work and costly and is done every 10-15 years.

In 2017, DNREC embarked on a 10-year update of Delaware’s statewide wetland maps. These maps use a computer analysis and the best technology available to draw wetlands of all types into a GIS layer and create a census of biological wetlands. These maps are hugely important for understanding what kind of wetlands Delaware has and how they are changing over time.

After much processing and quality checks we are excited to present several new wetland layers available to the public for access. Those readers familiar with the U.S. Fish and Wildlife Service NWI Wetland Mapper should note that Delaware has been updated with the 2017 data.

Another host for accessing and downloading new wetland maps is FirstMap under Hydrology as Delaware Wetlands where there are multiple layers available:

1. 2017 Wetlands- maps all types of wetlands by two classification schemes (NWI and LLWW). This layer now also includes surface water features from the NHD layer, so streams and ditches and rivers are mapped alongside wetlands in one place.

2. Wetland Trends- this layer was created by laying the 2017 wetland map over the 2007 wetland map and noting any differences (gains, losses or changes in wetland type). Some of the losses may have been permitted or naturally occurring. Some of the changes or shifts in wetland types were caused by natural processes such as sea level rise or succession.

3. High Marsh/Low Marsh – this is a brand new layer that serves as a baseline assessment of these habitat types to help track future response to climate change and sea level rise. Low marsh habitat would typically be dominated by Spartina alterniflora. High marsh habitat is likely to be Spartina patens, Iva frutescens, or Distichlis spicata.

Example of low marsh (left) and high marsh (right) data sets.

4. Ordinary High Water Line – depicts high water line along the coast, generally following the high marsh upper boundary, and can be useful for landuse planning to estimate the upper extent of tidal influence.

Example of high water line layer along coast.

5. As a historic reference the 1992 Wetlands and 2007 Wetlands layers are still available online.

These mapping layers represent biological wetlands and do not serve as regulatory or jurisdictional boundaries. Contact Watershed Assessment Section with questions or issues accessing or using these data at (302) 739-9939. 

Stay tuned for a story map that summarizes results from the new data and highlights the updated layers offered to the public. 

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Wetlands in an Urban Landscape: The Red Lion Watershed

Written on: September 17th, 2020 in Wetland Assessments

By Erin Dorset, Wetland Monitoring & Assessment Program

Most of our wetland assessments throughout the years have been in central and southern Delaware, but in the summer of 2017, our Wetland Monitoring and Assessment crew went north to perform wetland condition assessments at 116 wetlands in the Red Lion watershed. From protocol updates to navigating wetlands in a highly developed landscape, we certainly faced many new challenges. This year we finished analyzing the data from that summer, and now we can truly reflect on what we have learned!

We can now assess tidal freshwater wetland condition

A tidal freshwater wetland in the Red Lion watershed that is bordered by industrial development.

Our tidal wetland assessment protocol (MidTRAM) was originally designed only for salt marshes. However, Delaware is also home to tidal freshwater wetlands. Tidal freshwater wetlands are inherently different from salt marshes in many ways, such as water salinity and plant community. Such differences made our original protocol inappropriate for assessing tidal freshwater marshes.

Knowing that we would encounter many tidal freshwater marshes in the Red Lion watershed, we decided to update our tidal assessment protocol to incorporate those wetlands. To do so, we examined slightly different features for freshwater and saltwater tidal wetlands. We then graded them all on the same scale and combined them into one category for tidal wetland condition analyses. We were able to pilot test our updated tidal protocol (MidTRAM v.4.1) and learn a lot more about tidal freshwater wetlands in the process!

Wetlands in the Red Lion watershed are suffering

Wetland types in the Red Lion watershed based on 2007 state wetland maps.

The Red Lion watershed is in northern Delaware in New Castle county, encompassing 72 square miles. It includes part of the C&D Canal in the southern part of the watershed and Lums Pond State Park in the western part. In addition, it includes the populated areas of New Castle, Delaware City, Red Lion, and part of Bear.

In terms of land cover, the watershed is dominated by development, agriculture, and wetlands. Based on 2007 wetland maps, over half (54.9%) of wetlands are tidal, including saltwater wetlands (estuarine) and tidal freshwater wetlands (tidal palustrine). The rest of the wetlands are non-tidal flats (24.9%), non-tidal riverine wetlands (13.7%), or non-tidal depressions (6.5%). Overall, the watershed scored very poorly, receiving a D+ letter grade. Riverine and flat wetlands were in the best condition, with both wetland types receiving a B-. Depression and tidal wetlands were in much worse condition, receiving a D and a D-, respectively.

Urbanization comes at a price

Northern Delaware is more heavily developed than most of central and southern Delaware, which is dominated largely by agriculture. This makes northern Delaware a very different landscape within which to study wetland condition. In fact, we found that development, clearing for future development, and highway construction were by far the leading causes of wetland acreage loss in the Red Lion watershed between 1992 and 2007. Most wetlands that were gained during that same time period did not have any vegetation and were surrounded by development, limiting their ability to provide useful functions.

Example of a mapped non-tidal wetland loss (outlined in green) to development between 1992 (left) and 2007 (right).

As of 2017, the only other watershed that we had assessed in this urbanized area was the Christina River watershed. It came as no surprise to us that the Red Lion watershed was very similar to the Christina River watershed in terms of overall wetland condition. We found that 21% of wetlands were minimally stressed, 36% were moderately stressed, and 43% were severely stressed. The Red Lion and Christina River watersheds both had the highest proportion of severely stressed wetlands of any other watersheds that we’ve assessed.

Wetland condition comparisons among watersheds in Delaware.

One of the most widespread problems that we observed across all wetland types in the Red Lion watershed was the lack of natural surrounding land, or buffer. Development, roads, mowing, and other disturbances were commonly found in landscapes surrounding Red Lion wetlands. Without natural buffers, wetlands are more likely to experience issues like pollution and lack of suitable wildlife habitat. Tidal wetlands will also be unable to migrate inland as sea levels rise.

Habitat and hydrology issues

A flat wetland in the Red Lion watershed covered in the invasive plant mile-a-minute.

Like we have seen in many other watersheds, all wetland types in the Red Lion watershed suffered from the presence of invasive plant species, such as the European reed (Phragmites australis) and Japanese honeysuckle (Lonicera japonica). Invasive plants crowd out native plant species and reduce habitat value for wildlife that rely on native plants.

Many tidal wetlands also suffered from things like low plant species diversity and low marsh stability. Some non-tidal flats were ditched, causing water levels in those wetlands to be lower than they would be naturally. Numerous depressions contained nutrient indicator plant species. This suggests that many depressions may have had unnaturally high levels of nutrients within them from pollutant sources.

There are always ways for YOU to help wetlands!

As you can see, wetlands in the Red Lion watershed are in poor overall condition and they need your help! You can manage invasive species on your property so that they don’t expand into nearby wetlands. If you need help identifying plant species, you can download the Delaware Wetland Plant Guide for free! Other important things that you can do are to preserve or restore wetlands and wetland buffers on your land. You can also incorporate nature-based landscape designs where appropriate, such as living shorelines, rain barrels, or rain gardens. Additionally, you can help curb effects of pollution by limiting use of fertilizers and pesticides on lawns and gardens, washing cars on grass, and properly disposing of pet waste and chemicals.

Want to know more? Check out our newly released Red Lion Watershed Report and Report Card!

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Microplastics: A Not So Tiny Tale

Written on: September 17th, 2020 in Outreach

By Mike Mensinger, DNREC Coastal Programs

Humans rely heavily on plastics in the modern era. We produce and use plastics for many things in life including, but not limited to, product packaging, plastics bags, utensils and much more. Simply look around your current area and count the number of plastic products or components surrounding you. It’s quite likely more than you realize! Have you ever wondered what happens to plastic after fulfilling its original purpose? While recycling gives many plastic items a second use in life, vast amounts are discarded and make their way into the environment.

Clumps of plastic microfibers collected from the St. Jones River in Delaware.

Microplastics are tiny plastic pieces less than 5mm in size. They may enter the environment in their original form like microbeads previously used in things like skincare products and commonly referred to as primary microplastics. They may also enter as larger pieces, called secondary microplastics. Secondary microplastics break down into small pieces over time due to degradation from light, wind, water, etc. Unintended consequences of microplastics include aquatic critters like zooplankton and fish mistaking them for food. This may be harmful to them and organisms that feed upon them.

What is DNREC doing about microplastics?

Researchers from The Delaware Department of Natural Resources and Environmental Control’s (DNREC) Coastal Programs Section piloted a microplastics effort in 2016 using methods developed by the National Oceanic and Atmospheric Administration. The pilot paved the way for additional monitoring from 2017 to 2020. Environmental Scientists, Dr. Kari St. Laurent, Nicole Rodi, and Mike Mensinger along with dedicated interns, Rachael Faust and Sydney Hall investigated microplastics in the St. Jones River and nearby beach areas. While Nicole focused on river sediment and beach sand, Mike’s efforts focused on microplastics within the water itself as highlighted in this article.

A plankton net used for sampling microplastics in the water.

Mike conducted sampling every other month at Scotton Landing, a dock sitting on the south side of the St. Jones River. He deployed a plankton net, a sampling device with an appearance similar to a large mesh ice cream cone, which remained submerged near the water surface for two minutes. The net captured floating particles that flowed into the net’s open mouth and were funneled through the net body into a collection cup located at the net’s end.

Upon completion, the net’s contents were rinsed into a container and returned to the lab for processing and analysis. Once in the lab, samples were dried and exposed to a chemical mixture which dissolved the majority of organic matter. Next, salt was added to each sample to change its density, which caused the plastics to float at the surface while other materials sank to the bottom. The settled portion of the sample was drained away and the remainder drained through a mesh filter to that captured the microplastics. Mike later viewed each sample under the microscope to count and categorize each piece.

Results are coming soon!

Sample processing and analysis for this project’s 2018 and 2019 samples are currently nearing completion. Prior year results confirm presence of microplastics within the St. Jones River water. Detected microplastics include small broken pieces called fragments, thin hair-like pieces called fibers, and small round spheres called microbeads.

The project’s annual report will be available from the DNREC Division of Climate, Coastal and Energy’s Delaware Coastal Programs upon completion in the coming months, so stay tuned!

Click here to learn more about efforts to clean up marine debris, including microplastics, in Delaware!

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Dinophysis acuminata: a dinoflagellate you should know

Written on: September 17th, 2020 in Outreach

Guest Student Writer: Amanda K. Pappas, Delaware State University

What is a dinoflagellate?

Dinophysis acuminata preserved in Lugol’s iodine solution. Photo taken during the National Center for Marine Algae and Microbiota Harmful Algae Taxonomy Course at Bigelow Laboratory in 2019 (A. Pappas, 2019).

Dinoflagellates are a group of microscopic, mostly unicellular aquatic protists that are members of the plankton community. They live in fresh and marine waters, spanning the tropics to the arctic. Fossil records of dinoflagellates exist that are hundreds of millions of years old, so they have had some serious time evolving to their environments and the diversity of adaptations within the group showcases that.

Dinoflagellates are defined by two whip-like appendages they use to move called flagella. One wraps around the body for propulsion and the other extends out from the body for steering. The “brain-like” organelle of the dinoflagellate cell, the nucleus, is relatively large compared to those found in other unicellular creatures and looks like a human fingerprint. Dinoflagellates have a distinguishable cell covering known as a theca that is either “naked” for some or covered in an armor of cellulose in others.

Most are benign and mind their own business floating around providing food and oxygen to all, but some have the bonus of an ability to produce toxins. Toxin production in dinoflagellates is thought to be a means of avoiding predation and can be so potent they can cause illness in humans. This is an area our Dinophysis makes its debut.

Why study the Dinophysis acuminata dinoflagellate?

The genus Dinophysis consists of more than 100 species and they are too small to see without a microscope; 165 Dinophysis acuminata (D.a.) cells lined up “top to bottom” can fit across the diameter of your trusty #2 pencil eraser. In the 1970s another member of this genus, Dinophysis fortii, was identified as the culprit for sickness linked to contaminated shellfish in Japan through its production of toxins: okadaic acid and derivatives. The shellfish beds had to be shut down to harvests and this invisible miscreant has become a specimen of study almost everywhere.

In 2008, Texas experienced a similar situation Japan had, and the culprit that time was D.a. The economic hit communities take by closing recreational shellfish harvesting sites even for a season can lead to millions of lost dollars in lost venue. Areas with shellfish aquaculture industries are especially vulnerable and closures could lead to economic collapse for some areas reliant on the seasonal consumption of shellfish by tourists and national or worldwide sales.

2016 DSP World Map from the US National Office for Harmful Algae Blooms

The toxins produced by some members of the Dinophysis group lead to an illness known as Diarrhetic Shellfish Poisoning (DSP); can you guess the major symptom of the illness? Diarrhea along with other uncomfortable symptoms (i.e. pain, cramping, vomiting, chills, fever) occurs following consumption of filter feeding shellfish such as mussels, clams, scallops, cockles, and oysters that have accumulated okadaic acid in tissues. DSP toxins also promote tumor growth and may increase gastrointestinal cancer risk in humans with prolonged exposure. DSP toxins are not degraded by cooking and poisoning usually comes on quickly, within 30 minutes to a few hours after consumption and symptoms last 3-4 days. Symptoms can be severe or not and may go unrecognized as DSP poisoning due to the nonspecific symptoms in less severe cases. Aren’t you glad someone is keeping track of these things?

How do I study Dinophysis?

Dinophysis acuminata in culture. (Photo by A. Pappas and A. Williams, 2018)

My study site is in the Delaware Inland Bays, a group of shallow water bodies in south- eastern Delaware, with a flourishing oyster aquaculture industry. Torquay Canal, a dead-end residential canal up in the north- western corner of these bays, is a site with a history of D.a. bloom events. It is important to note this area is closed to shellfish harvest and no aquaculture takes place there.

D.a. is considered a harmful algae bloom (HAB) species. A bloom event of this species occurs when cell densities reach 20,000 cells per liter of water (cells/L) or more. Torquay Canal has had blooms in the millions! Whether a bloom event is harmful or not depends on the species and toxicity. Sometimes, high cell densities can be low in toxins and low cell densities may be high in toxins. Prey consumption, location, and strain all seem to influence toxin production in D.a. Increases in cell densities are known to occur due to increases in nutrient runoff (nitrogen and phosphorus) from land via fertilizers, faulty septics/sewage, and industrial discharge. Changes in wind direction, sunlight, temperature, and prey availability also contribute to increases in cell densities of D.a. Bloom events typically occur for this species at my study site during the spring and summer. I wanted to know if they were still there in the winter.

Some dinoflagellate life cycles involve a stage where the cell can encyst, creating a sort of encapsulation that allows the dinoflagellate to enter a state of dormancy quiescence during times where adequate resources are not in abundance, most often during winter months. These cysts are deposited in sediments, and act as inoculum to can start up future bloom events, and can be carried to other locations through wind and wave action. Whether or not D. acuminata produces cysts is not known; no one has seen one yet. So, I sought to answer, or at least scratch the surface, of a related question: Is D. a. present within the sediments of Torquay Canal during winter months?

I started by collecting sediment and water samples at Torquay Canal every month for two years.  The water samples I took for nitrogen and phosphorus analysis. Every time I sampled, I recorded information about the current water condition, like temperature, dissolved oxygen, pH, and salinity.  Dinoflagellate cells are packed with DNA, so instead of looking for something no one has ever seen, I extracted DNA from sediment samples using a chemistry kit made just for the application. 

After I had my DNA, I used a common molecular method called PCR (Polymerase Chain Reaction) to determine if the DNA I extracted belonged to Dinophysis.  Basically, you add DNA to a mixture of enzymes, reagents, and known segments of DNA you can purchase from a laboratory.  The known segments are called primers and they bind to either side of the DNA segment you are attempting to replicate that is unique to the organism you want to determine the presence of.  The mixture is heated up to break the double stranded helix of DNA in two strands and the primers and reagents all do what they naturally do: breaking, binding and copying through the heating and cooling.  The process continues until billions of copies of the DNA segment you are looking for end up in your little test tube or not.  It’s chemistry!

Then comes a trip to the post office to send out the samples to a sequencing lab to make sure you have what you aimed for.  The sequencing lab can determine the amino acid profile of your PCR product so you can check that to a database for accuracy.  Yes, there are databases full of DNA profiles for all kinds of organisms!

I am now analyzing results to determine if there are correlations between the results of the sediment analysis and nitrogen and phosphorus data.  The information obtained through this project will strengthen the harmful algae monitoring program in Delaware and add to the limited knowledge of D. a. within the Delaware Inland Bays.  I am looking forward to the mysteries we will uncover about this amazing creature! 

This project is directed by Dr. Gulnihal Ozbay (Advisor) at Delaware State University and Dr. Kathy Coyne at Delaware Sea Grant.

The NOAA LMRCSC provides funding for this project and is supported by the National Oceanic and Atmospheric Administration Educational Partnership Program with Minority Serving.

Institutions award NA 16 SEC 4810007.  The USDA provided funding for this project under the USDA NIFA Capacity Building Grant Award 201606642.  Delaware Sea Grant provided funding for this project under award R/HCE 32.

Dr. Ed Whereat (The University of Delaware Citizens Monitoring Program), Amanda Williams, Detbra Rosales, and Jen Wolny contributed to this project.

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It’s an Algae, It’s a Plankton, NO It’s SAV!

Written on: September 17th, 2020 in Outreach

By Michael Bott, DNREC Watershed Assessment and Management Section

Delaware’s Inland Bays (Rehoboth Bay, Indian River Bay, and Little Assawoman Bay) are home to many familiar animals such as finfish, crabs, and clams. But did you know that in addition to these aquatic animals, the Inland Bays are also home to many types of aquatic plants? Just like plants on land, these aquatic plants serve as the first link in the food chain and are foundational to the health of the underwater ecosystem. However, just like weeds in a garden, certain types of these aquatic plants can choke out other beneficial species if allowed to grow out of control.

These aquatic plants can be divided into three categories: macroalgae (“big algae”), planktonic algae (“little algae”), and submerged aquatic vegetation (“SAV”). While all three are essential components of the aquatic ecosystem, when present in large concentrations, both big and little algae can harm the ecosystem as well as constitute a nuisance to human enjoyment of the bays. For this reason, efforts are underway to control algae growth in the Inland Bays by limiting the runoff of nutrients from septic systems, lawn fertilizer, pet waste, and other sources into the bays. SAV, on the other hand, is the target of efforts to restore seagrass beds that have been decimated over the past several decades by poor water quality. In the Inland Bays watershed, the target levels of nitrogen and phosphorus in the water are based on the ability of the estuary to support the growth of SAV.

Since these aquatic plants have a big impact on the health of the Inland Bays ecosystem, these efforts to control big and little algae and then to restore SAV beds are critical to improving water quality so that humans and animals alike can continue to benefit from our Inland Bays. Let’s learn more about each of these three categories of aquatic plants in Delaware’s Inland Bays, and then learn about what you can do to help!

The Big Algae

Have you ever been wading or boating in Delaware’s Inland Bays and found yourself knee-deep in algae or found it wrapped around the prop of your boat? The culprits are macroalgae species such as Ulva, Gracilaria and Agardhiella, which in summer months commonly form large mats on the shore or in the shallow water of the Inland Bays.

Although macroalgae provides beneficial habitat to aquatic animals, at high densities it is very harmful to the Inland Bays ecosystem. When excess nutrients run off the land into the water, they act like a fertilizer for the macroalgae, allowing it to take over the bays just like weeds in a garden. The resulting high densities of macroalgae can smother aquatic animals and the beneficial SAV, as well as constitute a nuisance for people trying to enjoy the water.

The Little Algae

Discolored water under the ice caused by a widespread phytoplankton bloom in January 2019 (residential lagoon, Rehoboth Bay). Large phytoplankton blooms that color the water brown or green are very common during the summer, but these blooms can occur year round under the right conditions.

You may have also noticed that during the winter months the water normally seems very clear, but that during the summer the water appears very cloudy. Sometimes this is caused by rough weather or boats stirring up the water bottom, but often it is caused by microscopic algae blooms known as “phytoplankton” which when found in large numbers discolor the water.

Just like macroalgae, phytoplankton is essential to a healthy ecosystem because it provides food for many species but can easily become too much of a good thing if excess nutrients are introduced into the aquatic ecosystem. While most phytoplankton species are harmless to humans, there are also species that can produce toxins harmful to humans and wildlife, such as the infamous “red tides” that occur in the Gulf of Mexico. In Delaware, the greatest concern is that these large phytoplankton blooms may consume all the oxygen in the water, causing mass fish kills and other harmful effects to wildlife. The discolored water also blocks sunlight, which prevents beneficial SAV from getting the energy it needs to survive.

The Good Stuff!

Widgeon Grass growing in the Town of South Bethany canals during the summer of 2018. This is the species most likely to be encountered in the Inland Bays and can be found in a variety of salinities and waterbodies.

It may seem like all bad news, but there is hope on the horizon. Now for the first time in decades, you may start seeing beneficial SAV in the Inland Bays and its tributaries. If water quality begins to improve, the macroalgae and phytoplankton will have less nutrients to grow out of control. This allows SAV, such as eelgrass and widgeon grass, to receive the light needed to take hold and grow.

Because these beneficial SAV species are rooted instead of drifting throughout the water like algae, they help hold the sediment in place and thereby improve water clarity. SAV also dampens wave energy, reducing erosion of the important wetlands lining the bays. And, if water quality is high enough, these SAV beds eventually can form underwater meadows which provide critical habitat for juvenile fish, crabs, bay scallops and many other marine organisms.

Where They Can Be Found and How You Can Help

Currently the areas where SAV can be found are located on the State’s shellfish harvesting maps., which can be found at . These maps are constantly updated so if you find an area that you believe is an SAV bed that isn’t on the map, please share it with us ( so we can try and protect these important species as they begin to spread to new areas.

If you want to be part of this success story there are simple things you can do to reduce excess nutrients from flowing into the Inland Bays. Just like runoff from rainfall flows over the land into tributaries, water also flows beneath the land, contributing large amounts of excess nutrients to the estuary. Simple actions such as cleaning up pet waste in your yard, applying the correct amount of lawn fertilizer and maintaining your septic system in good working order are things everyone can do to help the health of the Bays. If everyone does what they can to improve water quality, hopefully we can reestablish healthy seagrass meadows and enjoy them for generations to come.

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Off the Rails: Studies on Delaware Clapper Rail

Written on: May 18th, 2020 in Wetland Animals

Guest Student Writer: Elisa Elizondo , Ph.D. Student, University of Delaware

Marsh Hens

Figure 1. A Clapper Rail nest near Mispillion River Harbor. Nests are typically raised above the marsh surface with some form of woven canopy.
Figure 1. A Clapper Rail nest near Mispillion River Harbor. Nests are typically raised above the marsh surface with some form of woven canopy. (Photo: Hailey Glasko , University of Delaware)

Colloquially known as marsh hens, the Clapper Rail (Rallus crepitans) is a vocal inhabitant of saltmarshes across the eastern coast of the United States and down into the Caribbean. Many of the first in-depth observations of Clapper Rail occurred in the mid-Atlantic, and in Delaware, Brooke Meanley documented much of their ecology. The northern Clapper Rail populations, including Delaware, have been declining based on extensive survey work conducted by the Saltmarsh Habitat Avian Research Program (SHARP).

Rails are typically secretive in nature, making their populations very difficult to monitor. One important measure of population health is nest survival, as the rate at which nests survive determines the number of offspring that can be produced to join the population in the following year.

Beginning in 2018, research conducted through the University of Delaware has been monitoring Clapper Rail nests in Delaware. Locating the nests can be tricky and is accomplished by searching on foot and using thermal imaging taken from a drone. Once a nest is located, the eggs can be floated in a container with freshwater to help determine their age. As the eggs develop, gas builds up within the egg ultimately causing it to float. When the eggs are close to hatching, they will float right to the top!

Often in the early stages of the nest, the adult rails are not spotted. When the eggs initiate hatching, however, the adults are at their most defensive. Both the male and female Clapper Rail incubate the nest and tend to the chicks. They employ various techniques to protect their nests including loud vocalizations, using their wings to appear larger, or feigning injury in the hopes of drawing off the predator. The chicks are ready to run into the marsh 1-2 hours after hatching, but currently there is no information on how many of those chicks make it to adulthood.

Figure 2. An egg with the very first cracks indicating that a chick is hatching (left) and a chick ~1 hour old (right). (Photo: Elisa Elizondo and Julie Bozzo , University of Delaware)

GPS Technology

In order to learn more about adult Clapper Rail survival and habitat use, the University of Delaware research crew is deploying GPS tags. These tags can be programmed to take GPS points throughout the day. Those data are then either sent to a satellite then downloaded online or downloaded manually by getting close enough to a bird to transmit the data to a handheld device (the download method varies by tag model).

Figure 3. A GPS tagged Clapper Rail at the Delaware Woodland Beach Wildlife Area
Figure 3. A GPS tagged Clapper Rail at the Delaware Woodland Beach Wildlife Area (Photo: Elisa Elizondo, University of Delaware)

Each tag can provide hundreds of locations that we can use to determine their territories. This helps us to determine what areas each individual bird is using and the overall types of habitat the birds seem to prefer. The satellite tags can continue to transmit for several years to help identify where the birds migrate to as well.

These data can sometimes yield surprising new information; in 2019 we discovered a tagged male bird with two nests ~5 m (approximately 16 feet) apart within his home range! Blood samples were drawn from both the adult and several chicks from the nests so that paternity can be evaluated in the lab.

Population Connectivity

There are 8 subspecies of Clapper Rail, and only the Northern Clapper Rail (R. c. crepitans) migrates. Here in Delaware, hunting band records from the 1950s and recent satellite data from birds tagged in Delaware indicate that Clapper Rail from Delaware winter in South Carolina and surrounding states. Understanding the population connectivity, or the degree to which populations interbreed, is important in determining population trends and areas of high conservation concern.

To determine the relationship of Clapper Rail in Delaware to other regions, blood samples are currently being collected from all tagged birds. Through collaborations with other state agencies and academic partners, additional samples will be collected from across the U.S. range of these subspecies to assess population connectivity using Next Generation Sequencing techniques. Given that Northern Clapper Rail populations seem to be in decline, it is increasingly important for us to understand how their populations relate to non-migratory subspecies.

Figure 4. A map depicting the Clapper Rail subspecies ranges. Data were produced through citizen science efforts, see to learn more.
Figure 4. A map depicting the Clapper Rail subspecies ranges. Data were produced through citizen science efforts, see to learn more.

This research is made possible by many funding resources, including the Delaware Department of Natural Resources and Environmental Control, the Delaware Ornithological Society, U.S. Fish and Wildlife Services, and the University of Delaware.

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