EVALUATING SPATIAL SOIL CHARACTERISTICS OF A MID-ATLANTIC DISTURBED SALT MARSH RESULTING FROM DREDGE SPOIL EMPLACEMENT AND OTHER ANTHROPOGENIC INFLUENCES

Historically, salt marshes at Greenbackville, Virginia were important for fisheries-centered industry, which with other anthropogenic disturbances have altered the integrity of the marsh. Oyster shucking activities and road building, in particular have produced numerous changes in natural tidal circulation. In addition, dredging operations to build the marina at Greenbackville, first in the 1930’s (CCC projects) and then completed by the Army Corps in the 1990’s, resulted in construction of a 46,000 m² settling basin completely surrounded by a 3 meter high berm. The basin is designed to allow settling to minimize sediment outflow into Chincoteague Bay after dredging. Emplacement of the settling basin has had dramatic impacts on the hydrology of the salt marsh, which are in addition to a number of other human disturbances (Kelsall et al., 2014). In an effort to investigate the impact of the dredge spoil on the salt marsh this research is focused on evaluating soil characteristics in transects across the spoil to marsh transition to further detail these impacts. Preliminary soil analysis from samples collected in 2013, show heterogeneous distributions of various soil components. Metals are variably distributed, in the preliminary samples. However the highest values for Zinc, Manganese, Copper, and Lead were found closest to the dredge spoil area. Soil pH characteristics show decreasing pH from near neutral (7.3) from the area of the spoil out into the marsh where pH was a minimum at 5.4. Given these observations, additional sampling is being carried out to further evaluate the patterns observed and determine if the trends are related to the spoil pile or other factors. For instance other fishery-related industries of the early 1900’s were active near the sites of some of these soil samples, including a barrel and canning factory. It is plausible that these industries (which pre-dated dredge spoil emplacement) may have contributed to higher metal concentrations in this immediate area, so additional transects away from historic building sites are being evaluated. Once analyzed the data will be used to develop mitigation strategies to improve the hydrology of the marsh system which may include re-establishing historic tidal creeks, and/or movement of dredge spoil material.