Center for Coastal Physical Oceanography

Celebrating 20 Years of CCPO

2011 Fall Seminar Series


J. Court Stevenson
UMCES Horn Point Laboratory

Monday, October 24, 2011
3:30 PM
Room 3200, Innovation Research Park Building I


Early work by Albert Redfield led to the paradigm that tidal marshes are in equilibrium with sea level. However, by the 1970s it became clear that, at least in some areas such as Louisiana, the Chesapeake Bay and Venice Lagoon, there were substantial marsh losses. As part of the Poplar Island Restoration Project in there is a plan to create 298 hectares of tidal marsh habitat, primarily using material dredged from shipping channels around Baltimore. Unlike the sandy material used in many coastal restoration projects, this material is fine-grained and very nutrient rich. The first wetland cell was constructed using locally obtained sand. Later cells were constructed with the upper Bay channel material, providing an on-site comparison. Striking differences in the vegetation developed on the two substrates, including sparser vegetation and higher recruitment of new species on sand. In contrast there was initially lush Spartina alterniflora, which eventually lodged, with intense muskrat grazing with high ratesof fungal infection in cells filled with channel material. Overall, above-ground biomass was very high (up to 3 kg m-2) and root:shoot ratios were much lower on dredged material, and dieback was common on dredged material, but not on sand. We hypothesize that the differences are due to the nutrient content and increased subsidence of the dredged materials. Since external inorganic sediment inputs are limited in this system due to the limited drainage area and sea walls, belowground biomass production is especially important for vertical accretion, which is necessary to keep abreast of local sea-level rise. The centennial rate is about ~3.2 mm y-1 in this segment of the Chesapeake Bay (and expected to at least double over the next century). Given the goal of creating self-sustaining marshes, healthy, productive marshes that contribute to vertical accretion are essential to the long-term success of the project. Thus far accretion rates have not been keeping up with sea level rise, but as habitat these restored marshes are attracting a wide variety of wildlife, ranging from fish, to amphibians and birds.


Dr. Stevenson received a B.S. in Biology from Brooklyn College, City University of New York and a Ph.D. in Botany from the University of North Carolina. His areas of expertise include the ecology of marsh and seagrass systems, including nitrogen cycling and productivity mechanisms, and the effect of sea level rise on coastal ecosystems.

Reception before seminar at 3:00 PM

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