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| Coastal
Ocean Studies
This Delaware Sea Grant research priority focuses on the “coastal ocean” — the area of the ocean nearest the shore where human impact is greatest. Researchers here are working to improve the scientific basis for assessing and managing the response of coastal waters and watersheds to human impacts. Embodied in this research is the need to establish linkages between land-use practices, shipping activity, ecosystem production, and coastal water quality. The following five Coastal Ocean projects have been funded by Delaware Sea Grant for the 2003–2005 period. They focus on the seas and shores of Delaware’s largest marine systems — the Delaware Bay and Delaware’s Inland Bays (Rehoboth, Indian River, and Little Assawoman bays).
For additional information, please also see our latest annual report. Ecohydrological Processes at
Freshwater Seeps Across Estuarine Beach Faces
Ancient Greek and Egyptian sailors knew of the existence of freshwater seeps along the coastline where drinking water could be collected during long ocean voyages. It is now believed that these submarine seeps may be responsible for up to 10% of the total freshwater input to estuaries and to the ocean. However, these seeps release more than just fresh water to the sea. They also transport nutrients and other
contaminants from the land and in more significant quantities than previously
estimated. An over-abundance of nutrients is a major problem in estuaries
like Delaware’s Inland Bays (Rehoboth, Indian River, and Little
Assawoman bays), where harmful algal blooms and large fish kills have
occurred in the past decade. In previous Sea Grant research, the scientists used thermal infrared imagery collected in winter by low-flying aircraft to identify seepage zones along the southwestern margin of Delaware Bay. They also analyzed in detail the hydrology, chemistry, and biology of a seep along the Delaware Bay at Cape Henlopen and several others in Indian River Bay in Delaware's Inland Bays. The objectives of the current project are to establish a permanent
observatory in the Inland Bays for the study of groundwater discharge
and associated hydrological, geochemical, and ecological processes.
The scientists want to determine the role of sandy beach-face sediments
in trapping and filtering nutrient-containing particles and the relative
importance of seepage in supporting the abundant biological productivity
found in these discharge zones.
The scientists have found that unique communities of organisms — mostly marine worms called polychaetes — inhabit these freshwater oases in the sea. For example, the red-gilled mud worm (Marenzellaria viridis) inhabits a freshwater seep in the Delaware Bay near Cape Henlopen. If it were not for the freshwater seep, the worm would not survive in the salty bay. The scientists also will explore the potential for bioremediation of
nutrient contaminants borne by freshwater seeps.
An Examination of the Physical Exchange Processes
in Little Assawoman Bay
Project: R/ME-33. Principal Investigator: Kuo-Chuin Wong University of Delaware Graduate College of Marine Studies, Newark Campus Project Period: Feb. 1, 2003 – Jan. 31, 2005
Aboard the 26-foot research vessel Captain Thomas White, UD
marine scientist Kuo-Chuin Wong prepares to release a current meter
into Little Assawoman Bay. The black sphere, about a foot in diameter,
will record the speed and direction of the water flow at this location
over the next 75 days. According to Wong, water circulation and exchange in Little Assawoman Bay can be forced by a variety of mechanisms over a broad range of time scales. ”On one end of the spectrum are first-order tidal motions that
operate on twice-daily time scales. At the other end of the spectrum
is gravitational circulation that varies mostly on seasonal time scales
and tidal mean flow," Wong notes. "Some of these processes,
such as the effect of local wind over the surface area of the bay and
the gravitational effect, are driven locally within Little Assawoman
Bay. However, much of the physical exchange in Little Assawoman Bay
is forced by processes operating in the adjacent estuarine and coastal
waters."
In the past decade, an unwelcome cast of characters has appeared in Delaware's Inland Bays. First it was Pfiesteria, then red tide, then brown tide. Then in 2000, Chattonella came on the scene, implicated as a "contributing factor" in a massive fish kill in Bald Eagle Creek. Chattonella and its companions are Harmful Algal Bloom (HAB) species — microscopic plants that can multiply rapidly, or "bloom," with often-devastating results for marine life. Some HAB species, like Chattonella, release toxins dangerous to fish and humans. During the next two years, UD marine scientists Mark Warner and David Hutchins will be working to find out what conditions trigger Chattonella blooms and exploring methods to control future outbreaks. "Lots of different algae live in our coastal waters," Warner says. "The algae that bloom are often superior competitors for available light and nutrients." In addition to examining how Chattonella responds to various light and nutrient levels, the scientists want to identify the bacteria and viruses that attack Chattonella in its natural environment.
"Such native biological controls may lead to practical ways of containing Chattonella blooms in the future," Hutchins notes. Currently, Hutchins’ laboratory is growing the local strain of Chattonella (Chattonella subsalsa) under various nutrient concentrations. So far, this work has revealed that Chattonella has a relatively high requirement for nitrate, which may be one reason why it thrives in the nutrient-rich waters of Delaware's Inland Bays. Warner’s laboratory is using several methods, including measuring chlorophyll fluorescence, to monitor the photosynthetic activity of the alga. Preliminary photosynthesis work indicates that Chattonella may be extremely tolerant of high levels of light. Like some other algal species, Chattonella moves by vertical migration, wherein the alga swims to the water surface during the day to capture sunlight for photosynthesis and then returns to the bottom to gain access to higher levels of nutrients later in the day. This tolerance to high light may allow Chattonella to out-compete other types of algae. Work is now under way to examine how the growth rate and photosynthetic capacity of Chattonella compares to other HAB species found in Delaware waters. Previous research in Hutchins’ laboratory has shown that a number of bacteria can control the growth and even kill other harmful algae, such as the dinoflagellate Pfiesteria piscicida. Work is now under way to investigate the potential of several strains of bacteria as well as marine viruses for controlling the growth of Chattonella. If such a biological control is identified, the mechanisms of growth inhibition will be studied in greater detail. The University of Delaware Research Foundation and the Center for the Inland Bays provided support for much of the preliminary work that led to this larger Sea Grant project.
Sediment Transport and
Deposition in the Upper Delaware Estuary on Tidal – Seasonal Time
Scales
Every year, on average, 1.4 million metric tons of sediment is washed into the Delaware Estuary from the Delaware River and adjoining tributaries. On average, 3.1 million metric tons of sediment per year is dredged from the shipping channel between Philadelphia and Wilmington by the U.S. Army Corps of Engineers. This massive quantity of sediment, which exceeds the annual river load, is testament to the intensity of sediment deposition in this industrialized corridor. Yet scientists are uncertain of the source of all this mud and how and when it gets deposited. In this Sea Grant research project, Chris Sommerfield, a marine geologist, and Kuo-Chuin Wong, a physical oceanographer, are working to identify zones of active sediment erosion and deposition in the upper Delaware Estuary and relate them to sediment sources, flow gradients, and natural versus human factors. This project is a follow-on to Sommerfield's previous Sea Grant project, from Feb. 1, 2001, to January 31, 2003, which yielded a wealth of new information on sedimentation processes in the upper Delaware Estuary. During that project, Sommerfield and his research team mapped over 300 miles of seafloor between Burlington, New Jersey, and New Castle, Delaware, using an oceanographic sensor called the towfish. Among their findings, the research team identified three distinct mud deposition centers within the Estuarine Turbidity Maximum (EMT) zone, which occurs between Chester, Pennsylvania, and New Castle, Delaware. Mud deposition is particularly intense near Marcus Hook, Pennsylvania; the two other major centers are located north and south of the Christina River. The seafloor in these areas consists of soupy mud. During the next two years, Sommerfield and Wong will conduct a series of research cruises aboard UD's 120-foot research vessel Cape Henlopen and the EPA's 35-foot research vessel Lear to deploy bottom instruments, conduct hydrographic surveys, and take sediment cores to sort out the physical factors affecting the sediment flow and concentration and to determine the total mass of sediment deposited during the study. Their ultimate goal is to produce an annual "sediment budget" for the estuary that pinpoints the sources of sediment inputs to the EMT zone. The research is expected to advance our fundamental understanding of the relationship between sediment transport, morphology, and stratigraphy of the upper Delaware Estuary and thus improve the scientific basis for managing related problems such as contaminated sediments, shoaling of the navigational channel, and impacts of subaqueous disposal of dredge spoils. It is being conducted in cooperation with the Delaware River Basin Commission, Delaware Department of Natural Resources and Environmental Control, and the EPA.
Currently, Phragmites australis is ranked as the number-one invasive plant in the Northeast by the U.S. Fish and Wildlife Service. Its fast-growing underground stems, called rhizomes, enable it to quickly take over a marsh, crowding out plants that are better for wildlife. In this latest Sea Grant project, UD marine botanists Jack Gallagher and Denise Seliskar are working to determine how various environmental conditions and stresses — such as salinity and flooding — affect rhizome growth. This information may lead to new techniques for controlling the plant's spread in wetlands, as well as advance the development of new strains of the plant for use as a "sludge buster" in wastewater treatment facilities. The plant's extensive root system helps Phragmites rapidly dry and break down treated waste, reducing sludge removal costs and landfill fees.
During the past decade, the UD research team has conducted a series of complementary studies focusing on Phragmites. With funding from Sea Grant and the Delaware Department of Natural Resources and Environmental Control, they examined the cycling of carbohydrates between the above- and below-ground portions of Phragmites, as well as the sensitivity of Phragmites to herbicide treatment at different stages of growth. This information helped the state pinpoint the optimum time to spray Phragmites with herbicide. With funding from Public Service Enterprise Group (PSEG), they determined the senstivity of the seedlings of five marsh plant species to sulfide, an environmental factor thought to be important in regulating the distribution of plants in the wetland landscape. With Sea Grant funding, they have analyzed wild strains of Phragmites and strains of the plant developed in their tissue culture laboratory for positive uses such as drying biosolids from watewater treatment facilities.They have examined 23 wild-type populations of Phragmites collected from along the Atlantic coast from Nova Scotia to Florida, along with a variegated line they developed, for qualities valuable in biosolids drying. The variegated line, called "Stripes," thus far has produced only albino seedlings that are, of course, not viable, making the plant unable to spread via seed, thus alleviating concerns of wastewater treatment operators that the plant would escape their facilities and invade marshes. Most recently, the scientists have examined the potential of certain wetland plants to "block" the re-invasion of Phragmites into wetland areas that have been cleared of Phragmites using herbicides. The scientists have found that yellow dock (Rumex crispus) has an inhibitory effect on Phragmites growth while salt-meadow hay (Spartina patens) does not. Black needle rush (Juncus roemerianus) is another potentially valuable "Phrag blocker" thanks to its extremely dense stems and root mat.
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   Copyright © University of Delaware College of Marine & Earth Studies and the Delaware Sea Grant College Program |
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