Where’s The Peak? Observations of Tidal Marsh Diversity Along The Patuxent and Nanticoke Rivers By Peter Sharpe and Andrew H. Baldwin The University of Maryland Department of Environmental Science and Technology May-August 2006

Research Objectives Describe plant species richness across a salinity gradient (fresh-brackish) in tidal marshes of two Chesapeake Bay Tributaries Salinity Richness Fresh Brackish Transitional Richness Salinity

Patuxent River Washington D.C.

Patuxent River Watershed Features Watershed Size – 2,356 km2 Gradient Length – 47 km Mean Tidal Range at Jug Bay – 0.73 m Land Use: 30% Agricultural 40% Forest 20% Urban 10% Other Land Uses Number of Survey Plots - 13

Patuxent River Washington D.C. Nanticoke River

Nanticoke River Watershed Features Watershed Size – 2,136 km2 Gradient Length – 56 km Mean Tidal Range at Sharptown, MD – 0.76 m Land Use: 48% Agricultural 41% Forest 2% Urban 8% Other Land Uses Number of Survey Plots - 16

Patuxent and Nanticoke River Study Sites Patuxent River Gradient – 47 km Nanticoke River Gradient – 56 km Seaford, DE Jug Bay Bivalve Harbor Benedict

Methods Vegetation surveyed using nested plot design consisting of a series of 10x10 m modules (Peet et al. 1998) 10 2 3 7 4 6 5 8 9 1 20 m 50 m Nest (Depth) Dimensions Area Depth 5 10 cm x 10 cm 0.01 m2 Depth 4 32 cm x 32 cm 0.1 m2 Depth 3 1m x 1m 1 m2 Depth 2 3.16m x 3.16m 10 m2 Depth 1 10m x 10m 100 m2 Residuals 20 m x 50m 1,000 m2 GPS Reading Piezometer Location SCT Reading

Typical Sampling Location High Marsh Levee Low Marsh Surveyed Area 10 m

Nanticoke River Species Richness Results (May-August) Residual Depth 1000 m2 Survey Area

Patuxent River Species Richness Results (May-August) Residuals 1000 m2 Survey Area

Conclusions Nanticoke River data show no immediate reduction in richness, actually an increase along the Nanticoke up to mean soil salinity of 3-4 ppt (peak observed at 0.8 ppt soil salinity) Patuxent River data show slight peak in June within limits of salt intrusion followed by maintenance of species richness along gradient up to 3 ppt Periodic salt water stress could promote coexistence of freshwater and brackish species Other potential factors: soil nutrient concentrations, marsh hydroperiods, toxicants, invasive species

Acknowledgements Project funding provided by the Maryland/D.C. Chapter of The Nature Conservancy through a Biodiversity Conservation Research Fund Grant Special thanks to Dr. Andrew Baldwin, Dr. David Tilley, Daniel Marcin, Robbie Vocke, Krissy Rusello, Douglas Rau, and Katherine Sharpe