Investigators: Dr. Mi-Ling Li

Like most temperate estuaries, the ecology and environmental conditions of Delaware Bay vary greatly over spatial and temporal scales and support a complex food web that couples benthic and pelagic productivity. Given the risk of serious PFAS contamination in the Delaware Bay and a wealth of knowledge regarding its food web structure, this project aims to use Delaware Bay as a field site to gain a better understanding of the spatiotemporal distribution and trophic transfer of PFAS in a temperate estuarine food web.

Investigator: Andrew McGowan, Delaware Center for the Inland Bays

Seagrasses are a vital component of a healthy estuary. They are a prime habitat for blue crabs and numerous fish species, sequester carbon, take up nutrients, dampen wave energy, and clear the water column of sediment. Despite their importance, no mapping has been done in the Inland Bays in over a decade, which means that remnant patches of seagrasses are vulnerable to unintended destruction from clamming, boating, and shoreline changes.

The Center for the Inland Bays will lead this Delaware Sea Grant-funded research project to locate, map, and assess the health of seagrasses in the Inland Bays using an innovative combination of low altitude drone flights and volunteer assisted ground surveys. Drones will be used to efficiently locate patches of submerged vegetation over the large area of the bays' shorelines, and patches of identified vegetation will be manually surveyed by staff and volunteers to identify if sea grasses are present, the boundaries of their distribution, and the overall density and health of the sea grass patches.

Efforts will target previously-mown seagrass locations, areas reported by the public to have seagrasses, and areas with water quality suspected to support seagrass growth. The data from this study will lead to the direct preservation of identified seagrass patches under newly created state regulations, and will also help state and local agencies identify areas for restoration or enhancement work. By performing this study, existing seagrass patches can be protected from damage, saving an irreplaceable habitat in the Inland Bays.

Investigators: Jonathan H. Cohen, Helga S. Huntley, Tracy L. DeLiberty, Tobias Kukulka

Microplastic marine debris (MPMD) is a pollutant of growing concern both globally and regionally. This Interdisciplinary Research Project integrates disparate land and ocean observations and models with expertise from the natural and social sciences to comprehensively assess the issue of MPMD in the Delaware Estuary.

Plastic marine debris is a pollutant of growing concern both regionally and globally. Since just a decade ago, about eight million metric tons of plastic have entered the ocean globally, largely due to coastal waste mismanagement.

Our approach combines GIS analysis of land surface and socio-economic data, MPMD abundance and material transport observations, numerical transport modeling, and biological effects data to estimate riverine sources of MPMD in the Delaware Estuary based on human activity, determine the importance of the Delaware River and lower bay tributaries as MPMD sources, identify transport and accumulation patterns of MPMD in the Delaware Estuary, assess MPMD abundance in the food web at accumulation zones, and integrate the GIS, field sampling, and model analyses to link land-use and environmental conditions with MPMD abundance in the Delaware Estuary ecosystem.

Investigators: Drs. Jennifer Biddle and Christopher Main

In Delaware, many waterways are deemed unhealthy or “impacted” due to high bacterial loads. While it is often thought that nutrient pollution stimulates microbial growth, microbes can also be washed into waterways from different sources. Current monitoring methods can’t distinguish these sources, meaning we are unable to tell the difference between pollution from humans and agriculture and bacterial loads which may come from wildlife.

This project is aimed at a better understanding of where the microorganisms in Delaware waterways are coming from. Researchers plan on using modern DNA sequencing methods to build a library of potential sources of contamination and then test three southern Delaware waterways to determine if the source of bacterial contamination can be idenitified. Researchers will share this data with state agencies that are responsible for management decisions regarding land use and environmental remediation.

Investigator: Dr. Carlos Moffat

The Prime Hook National Wildlife Refuge is undertaking a $38 million restoration project to return the 10,000-acre area to a naturally functioning tidal marsh and barrier beach capable of harboring migrating birds while preventing coastal flooding.

Delaware Sea Grant is funding research on how the Refuge will be affected by climate change, sea level rise, and human pressures in order to improve the resiliency of the Refuge following the restoration effort.

Drs. Chris Sommerfield and Carlos Moffat will measure sediment and water movement within the marsh. Tides, sediment loads, wind, and circulation patterns are all shifting as this restored ecosystem re-establishes balance, and ongoing data collection is necessary to keep resource managers aware of the progression of the restoration. In particular, it is important to monitor the delivery of sediment to the marsh since this directly determines the stability of tidal wetlands.

The research is being completed in partnership with the U.S. Fish and Wildlife Service and the Delaware Department of Natural Resources and Environmental Control. As data is collected, Drs. Sommerfield and Moffet will create a conceptual model of how the coastal ocean influences the exchange of sediment between Refuge and Delaware Bay.

While the science of restoration is advancing, many questions remain regarding how much of the original ecosystem functions and services will return or how long the restoration process will take. This research project will provide data critical to managing this restoration effort as well as advance the state of restoration science generally.
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Investigators: Drs. John Madsen and Dewayne Fox

The current population of Atlantic Sturgeon is less than 0.5% of the estimated historical stock in the Delaware River. The lower estuary hosts one of the largest remaining populations of Atlantic Sturgeon, although the reason why sturgeon congregate there is unknown.

Delaware Sea Grant is funding research to better understand the habitat preference of Atlantic Sturgeon in order to more effectively manage the estuary for the recovery of this endangered species.

At the start of the 20th century, the Delaware River supported the world’s largest caviar fishery dependent upon Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus). From a historic population numbering approximately 360,000 spawning adults, the current population is less than 0.5% of the estimated original stock. These declines and lack of recovery in this iconic species led to it being listed as endangered under the Endangered Species Act in 2012. Since Atlantic Sturgeon are not considered a sportfish, the State of Delaware has very limited means to support research and recovery activities for this species. Yet at the same time, the state, in addition to the federal government, has regulatory requirements to conserve and restore this population.

To allow for effective management of this species, fisheries scientists and decision makers need a more detailed picture of sturgeon habitat in Delaware waters. Researchers John Madsen and Dewayne Fox, from the University of Delaware and Delaware State University, respectively, will examine why adult and large sub-adult Atlantic Sturgeon congregate in the lower portion of the Delaware River estuary. That habitat area may host one of the largest remaining populations of Atlantic Sturgeon.

Drs. Madsen and Fox will use several techniques to collect data on the habitat preferences of adult and large sub-adult Atlantic Sturgeon during different life history stages. The research team will (1) deploy acoustic telemetry coupled with side-scan sonar to examine the distribution of sturgeon in space and time in the lower estuary; (2) catch and release sturgeon to examine their gut contents and determine their food sources while in the lower estuary; and (3) use side-scan sonar imagery, seafloor sediment sampling, and high-resolution bathymetry mapping to characterize the physical seafloor environment in the lower estuary.

Understanding why Atlantic Sturgeon congregate in the lower Delaware River estuary will greatly aid in stock assessment and survey design as well as support management decisions to minimize potential risks to this endangered species in this heavily utilized portion of the estuary. Specifically, the research will provide data that can be used to make science-based decisions concerning the designation of critical habitat for this endangered species. The project’s results will also help to meet the long-term goals of the Delaware Division of Fish and Wildlife, the Atlantic State Marine Fisheries Commission, of which the State of Delaware is a member, and the National Marine Fisheries Service of recovering the species to the point of delisting it as an endangered species and ultimately developing a sustainable Atlantic Sturgeon fishery.

Investigators: Drs. Tobias Kukulka and Jon Cohen

Plastic marine debris is an emerging pollutant of concern both in the Delaware estuary and around the globe. Delaware Sea Grant is funding research to quantify the distribution of microplastic debris in the Delaware Bay and its effect on marine organisms.

Plastic marine debris, particularly in the form of microplastics less than 5 millimeters in size, is an emerging pollutant of concern both in the Delaware estuary and around the globe. Microplastic debris can present serious hazards to individual marine organisms, but less is known about how microplastics impact entire communities and ecosystems – particularly with respect to important species in the Delaware Bay.

Delaware Sea Grant is funding Drs. Tobias Kukulka and Jon Cohen to quantify the distribution of microplastic debris in the Delaware Bay as it varies through space and time. In addition, the research team will develop a risk assessment model to quantify how increasing concentrations of microplastic debris impact the dominant zooplankton in the Delaware Bay, the copepod Acartia tonsa. The researchers will also develop an outreach program to engage and inform the public about the effects of microplastic debris on marine life, with emphasis on the ongoing work in Delaware Bay.

Investigator: Dr. Jack Puleo

Beaches provide not only recreation and leisure opportunities, but play an important role in protecting communities during intense storm events. At the same time, storms can dramatically alter the shape, extent, and height of beaches by moving sand along-shore and offshore.

Delaware Sea Grant is funding Dr. Jack Puleo to develop self-contained sensor systems for quantifying water and sand movement that can be rapidly deployed ahead of a storm event.

While beach characteristics and water movement around along a beach have been measured in detail before and after storm events, little data exists about how beach features change during a storm. Delaware Sea Grant is funding Dr. Jack Puleo to develop self-contained sensor systems for quantifying water and sand movement that can be rapidly deployed ahead of a storm event. Dr. Puleo will collect data using these sensor systems during at least two storm events on Delaware beaches, and then use modeling to predict how different shapes of beaches may respond to storm events of varying intensities.

This research will inform how vulnerable individual Delaware beaches are to erosion from coastal storms, allowing coastal managers to better direct efforts towards reducing beach loss. Dr. Puleo’s work will culminate in meetings with Delaware DNREC, US Army Corps of Engineers, and local town managers to ensure they benefit from the research findings.

Investigators: Drs. Tom McKenna, Naomi Bates, and John Callahan

An expanse of tidal wetlands fringes the Delaware Estuary and provides Delaware, Pennsylvania, and New Jersey with ecosystem services such as preserving water quality, mitigating flood hazards, and providing outdoor recreation.

However, these wetlands, particularly tidal saltmarshes, are highly sensitive to tidal inundation, which depends on factors such as coastal development, land use practices, coastal storms, and sea level rise.

Understanding the vulnerability of tidal saltmarshes to inundation requires precise mapping of the elevations of these wetlands relative to sea level. Currently, the Delaware Digital Elevation Model is the most widely used map of marsh elevations – however, this model is based on LIDAR measurements and has not been ground-truthed in many Delaware marshes, where thick vegetation may inhibit LIDAR’s accuracy.

Delaware Sea Grant is funding a team of Delaware Geological Survey researchers, led by Drs. Tom McKenna, Naomi Bates, and John Callahan, to improve our understanding of how tidal saltmarshes in the Delaware Estuary with respect to inundation. The research team will focus on four tidal saltmarshes: Blackbird Creek, Leipsic River, St. Jones River, and Murderkill River tributaries. In each marsh they will: (1) measure tidal cycles within the saltmarshes to determine how water moves through the marsh; (2) use spatial modeling to estimate marsh health and vulnerability to continued inundation; (3) identify systematic mistakes in the Delaware Digital Elevation Model caused by the thick vegetation present in saltmarshes; and (4) revise the Delaware Digital Elevation Model for Delaware saltmarshes from the City of New Castle to Broadkill Beach based on their findings.

Results from the study will be shared with natural resources managers and coastal scientists, particularly at the Delaware National Estuarine Research Reserve and the US Fish and Wildlife Service. Additionally, the team will work closely with the North Bay Adventure Camp and other groups to help develop K-12 and higher education materials to provide high quality educational programming. Overall, this study will aid coastal managers in planning long-term resilience to sea level rise using tidal saltmarshes as a natural barrier.

Investigator: Dr. Kathryn Coyne

Dinophysis acuminata is a toxic microalgae found in Delaware’s Inland Bays that can bloom to concentrations that are harmful to fish and other wildlife and may pose a threat to shellfish aquaculture in the bays.

Researchers suspect that a controlling factor in blooms of this organism may be the abundance of another, non-toxic algae, Heterosigma akashiwo, since blooms of Dinophysis typically occur simultaneously with blooms of Heterosigma and the latter could serve as prey for Dinophysis. Delaware Sea Grant is funding Drs. Tye Pettay and Kathy Coyne to better understand the relationship between these two algae in order to improve our ability to predict, respond to, and treat harmful algal blooms and manage the risk to the shellfish aquaculture industry.

Dinophysis acuminata is a toxic microalgae found in Delaware’s Inland Bays that can bloom to concentrations that are harmful to fish and other wildlife and may pose a threat to shellfish aquaculture in the bays. Little is known about the ecology of Dinophysis, including the environmental factors that enable it to bloom. However, researchers suspect that a controlling factor may be the abundance of another, non-toxic algae, Heterosigma akashiwo, since blooms of Dinophysis typically occur simultaneously with blooms of Heterosigma and the latter could potentially serve as prey for Dinophysis.

Delaware Sea Grant is funding Drs. Kathy Coyne and Tye Pettay to better understand the relationship between these two algae in order to improve our ability to predict, respond to, and treat harmful algal blooms and manage the risk to the shellfish aquaculture industry. The research team will use molecular tools coupled with laboratory feeding experiments to determine whether Dinophysis uses Heterosigma as a source of prey. Field sampling will identify how resting stages of Dinophysis may survive in bay-floor sediments during the winter, and how these resting stages trigger a bloom. Intensive sampling during blooms will further help to evaluate environmental drives of Dinophysis and Heterosigma blooms, and will help to predict the risk of Dinophysis spreading to shellfish aquaculture operations within the Inland Bays. In addition, the research team will establish a Mid-Atlantic working group on Dinophysis to bring together regional experts on toxic algae, shellfish biology, and aquaculture.