Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
2 results
Search Results
Item Ecosystem dynamics in tidal marshes constructed with fine grained, nutrient rich dredged material(2015) Staver, Lorie Winchell; Stevenson, J. Court; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An ecological study was undertaken of the tidal marshes at Poplar Island, a restoration project utilizing fine grained dredged material from the shipping channels in upper Chesapeake Bay. The goals of the study were to examine the effect of a nutrient rich substrate on vegetation development, elevation change, and nutrient cycling in the constructed tidal marshes. Specifically, I examined macrophyte production, nitrogen (N), carbon (C) and silicon (Si) budgets, as well as the success of a silica amendment in enriching plant tissue concentrations. Establishment of Spartina alterniflora and S. patens on fine grained dredged material was rapid, and growth peaked in the second year. Thereafter S. alterniflora dieback occurred sporadically during the growing season, but the causes remain unclear. Elevation change averaged 7.9 ±0.8 mm y-1 in the dredged material marshes (low marsh only), compared to 7.4 ±1.4 mm y-1 in a low nutrient onsite reference marsh. Elevation change was significantly correlated with biomass production suggesting that inputs of organic matter from high rates of aboveground biomass production on nutrient rich dredged material offset the reduced contribution of belowground biomass to vertical accretion. However, dieback may have a detrimental effect on vertical accretion, which is essential for keeping up with apparent sea level rise (13.6 and 11.0 mm y-1 at Baltimore and Solomon’s tide gauges, respectively) since elevation monitoring began at Poplar Island. The tidal flux study revealed that the marsh exports ~665 kg of N y-1, including 100 kg NH4+-N y-1, and 67,874 kg y-1 TSS, and imports 35 kg NO3-N y-1. Silicon is also exported on both a seasonal and annual basis, including 4,337 kg dissolved Si y-1 and 3,924 kg biogenic Si y-1, with highest exports in July, an overlooked benefit of dredged material restoration projects. Soil Si amendments increased plant tissue concentrations significantly, but this study did not show increased resistance to N related stress effects on the vegetation. Overall, this study suggests that when considering trajectories of vegetation development, nutrient exchanges and elevation change in constructed marshes, it is essential to consider the initial nitrogen content of the substrate.Item MARSH ELEVATION AND ACCRETION DYNAMICS ALONG ESTUARINE SALINITY GRADIENTS: OBSERVATIONAL AND EXPERIMENTAL STUDIES(2009) Beckett, Leah Hope-Menzies; Baldwin, Andrew H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Chesapeake Bay marshes are threatened by sea level rise and have experienced degradation as a result of saltwater intrusion and increased water levels. Rates of elevation and accretion change and vegetation communities may be affected by salt water intrusion and other processes as a result of sea level rise. An observational study of the Nanticoke River, a tributary to the Chesapeake Bay, utilizing surface elevation tables (SET) reflected that during the course of a two year study period, rates of marsh elevation change differed significantly along an estuarine salinity gradient. Surface elevation of oligohaline marshes decreased during the monitoring period and were significantly different from mesohaline marshes which increased in elevation. An experimental study in Patuxent River tidal freshwater marshes in which plots were irrigated with saltwater indicated that with saltwater intrusion vegetation communities may become less diverse.