Stability, Sampling, and Subaqueous Soils of the Rhode River Estuary.

The Rhode River estuary, a sub-estuary of the Chesapeake Bay, covers approximately 1000 ac of subaqueous landscape near Annapolis, MD. In freshwater and coastal subaqueous landscapes, the four soil forming processes of additions, removals, translocations, and transformations have been shown to operate, but the subaqueous soil concept had not yet been extended to the Chesapeake Bay. One of the arguments forestalling the application of soil mapping techniques to such tidal estuaries is that the landforms in these systems are too unstable through time for soil maps to be of use. However, detailed bathymetric surveys of the Rhode River estuary were conducted in 1846, 1903, 1933, and 1972. Between 1933 and 1972, depth changes were less than one foot in most areas and the surveyors recommended that the estuary be surveyed on a 50-year cycle, ample time for a soil map to be of use. Data from these surveys has been and will continue to be digitized and analyzed in a GIS to obtain a greater understanding of subaqueous landscape change through time; contemporary data will be collected using a depth-sounder and included in this analysis. Side-scanning sonar will be used to characterize the epibenthos. Once contemporary subaqueous landform units are identified, core samples will be taken along transects crossing each of these units using a peat auger or vibracorer. Cores will extend 1-2 m into the substrate, and several cores will extend to the depth of refusal to obtain samples of the pre-siltation soil. Core profiles will be described, identifying distinct horizons. Texture, color, pH, fluidity, structure, shell fragment abundance, organic matter content, and sulfidic material presence will be recorded. Soil series will be described and mapped to characterize this subaqueous landscape in order to inform oyster reef placement, dredged material disposal, and blue-carbon accounting.