Ecological Research on Wetlands and Submersed Aquatic Vegetation

Wetland importance
    Project description and publications

Submersed aquatic vegetation investigations in Chesapeake Bay
    Bibliography of USGS investigations in Chesapeake Bay
    Timeline of important events in the history of SAV and Trapa natans in the Potomac River
    Links to submersed aquatic vegetation and Chesapeake Bay information

Vegetative resistance to flow investigations in the Florida Everglades
    Links to South Florida ecosystem information

Water, energy, and biogeochemical budget (WEBB) and the interdisciplinary research initiative (IRI)

   Since 1978 this project has been involved in studies to determine factors affecting the distribution and abundance of submersed aquatic vegetation and the effect of submersed aquatic vegetation on water quality and flow.  Starting in 1978, U.S. Geological Survey personnel have monitored the distribution of SAV in the freshwater tidal Potomac River.  The Geological Survey conducts a shoreline survey of the tidal Potomac River as far south as Maryland Point, estimating coverage of SAV and percent cover by species (Ruhl et al. 1999).  Information on species distribution and SAV density are supplied to the Virginia Institute of Marine Science (VIMS) to complement the annual bay-wide survey of SAV and/or the Metropolitan Washington Council of Governments (COG) to help in their aquatic plant control program.  The monitoring data have been used in many of the reports in the project bibliography.

    The project has conducted research on factors affecting the distribution and abundance of SAV in the freshwater tidal Potomac River and the oligohaline Potomac River Estuary in order to supply information relevant to the restoration of SAV.  The Geological Survey cooperated with VIMS, the Environmental Protection Agency, the University of Maryland, and Harford Community College to develop the document Submerged Aquatic Vegetation Habitat Requirements and Restoration Targets: a Technical Synthesis, published in 1992. (Batiuk et al. 1992).  Input to the technical synthesis document consisted of results of prior research on the factors affecting distribution and abundance of SAV and analysis of water-quality data gathered by the Geological Survey and by the states of Maryland and Virginia and the District of Columbia.  The Geological Survey made a detailed analysis of water-quality and weather data for the tidal Potomac River between 1980 and 1989 (Carter et al. 1994).  As suggested in an earlier publication (Carter and Rybicki 1990), they determined that available light was the primary factor controlling distribution in the tidal river, but, in addition,  weather played an important role.  A mean seasonal (April through October) Secchi depth of <0.65 m generally resulted in a decrease in vegetation in both the upper tidal River (Washington, D.C. to Marshall Hall) and the lower tidal river (Marshall Hall to Quantico).  Significantly greater than average available sunshine and lower wind speed helped with re-establishment of SAV in 1983, and lower than average sunshine and greater than average wind speed was partially to blame for the disappearance of much of the Hydrilla verticillata in the upper tidal river in 1989.

    The Geological Survey also conducted field experiments that demonstrated that beds of SAV were capable of altering the ambient water quality in the tidal river, increasing oxygen and pH during the daylight hours and maintaining clear water with low total suspended sediment and chlorophyll a in the beds (Carter et al. 1991).  Field studies also showed that dense beds of submersed macrophytes altered flow velocity and could cause water levels to rise and fall more slowly in the bed than in the channel.  This sets up a water-level gradient between the bed and the channel.  This gradient causes flow in the bed. The Wetlands/SAV research team investigates a broad range of ecological topics in Chesapeake Bay, its tributaries, and in Florida Everglades.