Conference proceeding
Ecohydrologic controls on groundwater salinity, carbon, nutrients, and disturbance recovery in a tidal freshwater wetland
Biennial CERF Conference, 24
2017
Abstract
Tidal freshwater wetlands fringe many productive coasts but their solute balances are distinct and less known than saline tidal marshes and estuaries. We investigated effects of vegetation and surface water (SW) – groundwater (GW) exchange on the salinity (EC), Cl-, dissolved organic carbon (DOC), and nutrients (N, P) in the root zone of a tidal freshwater wetland in Wax Lake Delta, LA. We sampled GW under two dominant plant types at 10, 30, 50cm, and SW. GW under Salix nigra was higher in EC, Cl-, and DOC than under Colocasia esculenta, explained by lower SW infiltration (higher elevation) and higher evapotranspiration (larger leaf area index) for S. nigra. Uniformly low nutrient concentrations suggested a capacity for deep root zone sediments under either plant type to help mitigate coastal nutrient loads. DOC in GW was up to 10 times higher than in SW and tracked spatial EC patterns, perhaps due to higher microbial degradation of organic matter with higher salinity. This high GW DOC could be an unrecognized coastal C source, exported by GW-SW exchange. If relative sea level rise and anthropogenically-reduced river discharge raise marsh GW salinity, the deep marsh GW DOC pool and DOC export to the coastal zone may increase. GW was generally higher in EC and Cl- than SW but lower in nutrients, likely due to GW evapoconcentration and marsh nutrient uptake. A coupled water and Cl- mass balance model predicted effects of variable weather, rain, and SW infiltration on GW salinity, and estimated a ~15 year timescale for the system to equilibrate after disturbance. The model that matched observed Cl- variability also matched independent evapotranspiration, GW discharge, and SW infiltration rate estimates, if assumed constant since the island attained its present morphology and vegetation. Eco-geomorphological feedbacks in freshwater tidal marshes thus appear to extend to biogeochemical effects.
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Details
- Title
- Ecohydrologic controls on groundwater salinity, carbon, nutrients, and disturbance recovery in a tidal freshwater wetland
- Creators
- Peter B ZamoraKevan B MoffettMarc G KramerJohn Harrison
- Conference
- Biennial CERF Conference, 24
- Academic Unit
- Environment, School of the (CAS)
- Publisher
- CERF
- Identifiers
- 99900669520001842
- Language
- English
- Resource Type
- Conference proceeding