| Patuxent Science Meeting 2006 Poster Abstract |
| | Deterioration of a Mid-Atlantic coastal marsh |
| | Soeder DJ, Birch DL (FWS) |
| | Blackwater National Wildlife Refuge was established in 1933 as a way-station for migratory |
| | birds along nearly the entire reach of the Blackwater River in Dorchester County, on Maryland's |
| | Eastern Shore. The 26,000-acre refuge is composed mainly of Chesapeake Bay tidal marsh, |
| | characterized by fluctuating water levels and salinity gradients. Deterioration and loss of |
| | marshland and forested wetlands at the refuge is significant. Aerial photographs from 1938 |
| | show a relatively intact marsh along the Blackwater River with only a few small ponds. By |
| | 1985, however, the marsh had degraded into large tracts of open water, and current wetland |
| | losses are estimated at 7,000 to 8,000 acres. Contributing factors may include rising sea level, |
| | invasive species such as nutria (Myocastor coypus), degraded water quality, and human |
| | activities, although the relative impacts of these are poorly understood. Observations show that |
| | erosion of the marsh is occurring at a rapid rate, and vertical accretion is not keeping pace with |
| | sea-level rise. Research indicates that restricted tidal exchange within the marsh may be a |
| | critical factor, with impounded water causing deterioration of the largely organic, peat-rich |
| | substrate through the action of trapped sulfides, low dissolved oxygen, build-up of nutrients, or |
| | some combination of factors. Saltwater intrusion into formerly freshwater areas due to marsh |
| | deterioration at a watershed divide, and plans for the construction of several large housing |
| | developments within a tributary watershed are but two of several issues of concern to the refuge |
| | management. Better hydrologic characterization of the marsh is needed to help understand the |
| | impacts of these and other problems at the refuge. Precise tidal-stage data, salinity |
| | measurements, streamflow, ground-water and water-quality analyses have all been proposed, |
| | along with LIDAR elevation studies, sediment accretion measurements, and substrate coring to |
| | achieve a better understanding of the physical, geological, geochemical, and hydrologic |
| | processes operating in the marsh. The effectiveness of any planned restoration may be |
| | dependent upon the knowledge of marsh hydrology and the underlying causes of wetland loss, |
| | neither of which are currently well understood. The time frame for such studies may be short, |
| | however; one proposal under consideration will re-build the marsh by adding dredge spoils from |
| | Baltimore Harbor at the rate of 30 million tons per year over 10 years. The problems of |
| | Blackwater are relevant to wetland science in the neighboring Delaware Estuary, because the |
| | fringe marshes there are facing similar threats. Land-use changes, pressure from real estate |
| | development, habitat loss, degraded water quality, invasive species, and rising sea levels are |
| | issues in the Delaware Estuary as well as in the Chesapeake Bay. The pressure to dredge and |
| | to use the dredge spoils in a constructive manner has also been a concern in the Delaware |
| | Estuary. The applicable issue from Blackwater is that the performance of a wetland "restored" |
| | Friday, September 22, 2006 |