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| Ecosystems
The goal of this research priority is to expand the scientific and policy basis critical to sound ecosystem-based management in the wise use, protection, and restoration of coastal waters, estuaries, and watersheds and their living marine resources. The following two Ecosystems projects have been funded by Delaware Sea Grant for the 2005–2007 period:
For additional information, please also see our latest annual report. How Do Changes in Physical Conditions
and Megalopae Behavior Affect Blue Crab Recruitment Variability in
Chesapeake and Delaware Bays?
The blue crab (Callinectes sapidus) is of major economic importance in the Mid-Atlantic region and supports one of the largest inshore fisheries in the states of Delaware, Maryland, and Virginia. As a result, year-to-year variations in the blue crab population can have a large economic impact in these states. The variations depend on the number of juvenile crabs (megalopae) that enter the population, or are “recruited,” each year. Previous field investigations indicate that blue crab larvae are spawned at the mouths of bays in the Mid-Atlantic, including the Delaware and Chesapeake bays, from June through August. The baby blue crabs (zoea) are swept out of the bay by southward flowing currents, where they grow and develop into megalopae. Summer winds then push the juvenile crabs back into the bays after approximately 4 to 6 weeks. Much research has been conducted to determine how various biological and physical processes control the recruitment of young crabs each year. However, recent studies indicate that there are significant gaps in the understanding of how these processes work in tandem and whether or not there is any biological or physical interaction between the Delaware and Chesapeake bays. In this Sea Grant project, marine biologist Charles Epifanio and oceanographer Richard Garvine at the University of Delaware College of Marine and Earth Studies will team up with scientists at the Horn Point Laboratory at the University of Maryland Center for Environmental Science in Cambridge, Maryland, and Old Dominion University in Norfolk, Virginia, to determine how changes in physical conditions and megalopae behavior affect blue crab recruitment variability in the Chesapeake and Delaware bays. More specifically, the scientists will look at the vertical distribution of blue crab megalopae in the water column to identify mechanisms that influence their transport into the Chesapeake and Delaware estuaries. This information will be used with monitoring data and numerical models to determine how differences in freshwater flow affect blue crab recruitment.
Improving
Water Quality and Maintaining Salt-Marsh Surface Elevation by Exploiting
Intraspecific Variation in the Ability of Marsh Plants to Sequester
Nutrients and Carbon
Wetlands play an essential role in keeping the waters of estuaries and bays clean. The grasses, shrubs, and other plants that live in these areas have the ability to filter nutrients, such as nitrogen and phosphorus, that is found in upland runoff, by taking them up and storing them.The nutrients are then released at a later time. Unfortunately, as coastal development continues, wetland areas have been disappearing at an alarming rate. As a result, agricultural runoff and sewage is discharged almost directly into the bays increasing the concentration of nutrients in estuarine waters. The increased concentration of nutrients encourages plant and algal growth and can result in what is called an “algal bloom” – a situation that occurs when an algal species grows so fast it can deplete the water of oxygen. These species thrive in stressed estuaries like Delaware’s Inland Bays, for example. According to marine botanists John Gallagher, professor of marine biology and biochemistry and co-director of the Halophyte Biotechnology Center at the University of Delaware in Lewes, and Denise Seliskar, research scientist and co-director of the Halophyte Biotechnology Center, an increased awareness of the role that wetlands play in acting as a filter, or buffer, between upland areas and estuaries has led to efforts to protect and restore these areas. “There are, however, many factors to be considered when planning the restoration or creation of wetlands,” says Gallagher. “We want to identify those plants that have a superior ability to not only filter and sequester nutrients from upland runoff and seepage that moves over or through the marsh soil, but also release these nutrients when the detrimental impacts to the estuarine water will be minimized.” Seliskar adds that it also is important to identify those plants that direct most of their photosynthetic activity into organic material below ground, such as into the plant’s roots. These plants have the added benefit of increasing the elevation of the marsh surface as sea level rises, thus maintaining the area as an intertidal marsh. In addition, these plants are important in creating soils for marsh development because this below ground organic matter decays very slowly. In this Sea Grant project, Gallagher and Seliskar will analyze the variation in the ability of four salt-marsh plant species to not only filter and sequester nutrients, but also produce most of their biomass below ground. These plant species – Spartina alterniflora, Spartina patens, Juncus roemerianus, and Baccharis halimifolia – are commonly found along the Atlantic and Gulf coasts, which makes them more attractive for restoration efforts. It is often more desirable to use a native plant species than a non-native that may become invasive. 
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   Copyright © University of Delaware College of Marine & Earth Studies and the Delaware Sea Grant College Program |
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