Neponset River Estuary Assessment Lynn Ficarra General Characteristics • • • • • • From Walter Baker Dam to Dorchester Bay1 7 km long2 25-250 m wide at low tide, up to 1 km at high tide2 Depth ranges from <2-4 m at low tide2 3 m tidal range3 Large portion of water in estuary exchanged at each tide3 • Surface area 0.88 km2 at low tide, 2.17 km2 at high tide2 • River flow through dam 0.6-3.1 m3/s Neponset River Estuary1 • • • • Shallow Tidally dominant2 Probably well-mixed Vertical salinity stratification unknown • Total volume of water in estuary unknown • Bottom topography unknown Habitats Salt marsh4 – Was dominated by native Smooth cordgrass (Spartina alterniflora) and Saltmeadow cordgrass (Spartina patens) – Now invasive Common reed (Phragmites australis) Spartina alterniflora Spartina patens Phragmites australis – Past dredging, loss of natives, opportunity for invasives to move in5 Habitats cont. • Mud flats2 • Intertidal: 29% non-vegetated2 Habitat cont. • In 1991, estuary had 311.64 acres of wetlands5 – 25.92 acres of non-vegetated wetland – 265.67 acres of salt marsh – 20.05 acres of common reed marsh • But what about today? – All remaining salt marshes degraded7 • Sediment characters unknown Organisms • Anadromous fisheries4 – Rainbow smelt American shad – Herring – American shad • River dams shortened runs4 and pollution lead to declining fish populations6 • Nursery4 • Hunting grounds4 Herring Rainbow smelt Residence Time2 • ≤1 day Nutrient Limitation7 • Nitrogen limited Conclusions • A lot of missing data • Outdated information • Projects – Remove dam to improve fish populations – Restore salt marshes • Will eelgrass and oysters help? References 1. 2. 3. 4. 5. 6. 7. Breault R.F. 2011. Concentrations, Loads, and Sources of Polychlorinated Biphenyls, Neponset River and Neponset River Estuary, Eastern Massachusetts. U.S. Geological Survey Scientific Investigations Report 2011-5004, 143 p. Gardner G.B., R.F. Chen, and A. Berry. 2005. High-resolution measurements of chromophoric dissolved organic matter (CDOM) in the Neponset River Estuary, Boston Harbor, MA. Marine Chemistry. Vol. 96:137-154. Zhu J. and C.R. Olsen. 2009. Beryllium-7 atmospheric deposition and sediment inventories in the Neponset River estuary, Massachusetts, USA. Journal of Environmental Radioactivity. Vol. 100:192-197. NepRWA. 2006. Neponset Salt Marsh Restoration. The Neponset River Watershed Association. http://www.neponset.org/Restoration-SaltMarsh.htm Tiner R.W., D.B. Foulis, C. Nichols, S. Schaller, D. Petersen, K. Andersen, and J. Swords. 1998. Wetland Status and Recent Trends for the Neponset Watershed, Massachusetts (1977-1991). U.S. Fish and Wildlife Service National Wetlands Inventory Project Northeast Region. 32 p. Massachusetts Government. 1998. Neponset River Subwatershed-River and Estuary Segment Assessments. Boston Harbor Watershed 1999 Water Quality Assessment Report. p. 87-188. NepRWA. 2004. Neponset River Watershed 2004 Assessment Report. Massachusetts Executive Office of Environmental Affairs. 56 p.