This research was funded in part by The Nature Conservancy through a grant to JPM and in part through a Fellowship to JLM from the Environmental Science and Policy Department at George Mason University.
Marsh ecology -- Atlantic Coast (U.S.), Marsh ecology, Freshwater ecology, Mattaponi River (Va.), Mattaponi River (Va.) -- Environmental conditions
Sediment deposition is the main mechanism of nutrient delivery to tidal freshwater marshes (TFMs). We quantified sediment nutrient accumulation in TFMs upstream and downstream of a proposed water withdrawal project on the Mattaponi River, Virginia. Our goal was to assess nutrient availability by comparing relative rates of carbon (C), nitrogen (N), and phosphorus (P) accumulated in sediments with the C, N, and P stoichiometries of surface soils and above ground plant tissues. Surface soil nutrient contents (0.60–0.92% N and 0.09–0.13% P) were low but within reported ranges for TFMs in the eastern US. In both marshes, soil nutrient pools and C, N, and P stoichiometries were closely associated with sedimentation patterns. Differences between marshes were more striking than spatial variations within marshes: both C, N, and P accumulation during summer, and annual P accumulation rates (0.16 and 0.04 g P m−2 year−1, respectively) in sediments were significantly higher at the downstream than at the upstream marsh. Nitrogen:P ratiosbiomass, surface soils, and sediments suggest that N limits primary production in these marshes, but experimental additions of N and/or P did not significantly increase above ground productivity in either marsh. Lower soil N:P ratios are consistent with higher rates of sediment P accumulation at the downstream site, perhaps due to its greater proximity to the estuarine turbidity maximum.
Morse, J. L., Megonigal, J. P., & Walbridge, M. R. (2004). Sediment nutrient accumulation and nutrient availability in two tidal freshwater marshes along the Mattaponi River, Virginia, USA. Biogeochemistry [Dordrecht], 69(2), 175-206.