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  Archived Posts From: 2020


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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