Porewater chemistry measurements from the GCE-LTER Seawater Addition Long-Term Experiment (SALTEx)

The Georgia Coastal Ecosystems LTER Seawater Addition Long-Term Experiment (SALTEx) is a large-scale field experiment designed to simulate saltwater intrusion in a tidal freshwater wetland to predict how chronic (Press) and acute (Pulse) salinization will affect this and other tidal freshwater ecosystems. The SALTEx experiment was initiated in 2012 and consists of 31 field plots, each 2.5 m on a side. There are three treatments (Press, Pulse, and Fresh) and two types of controls (with and without sides), each consisting of six replicates. The Press treatment plots receive regular (4 times each week) additions of a mixture of seawater and fresh river water. Pulse plots receive the same mixture of seawater and river water during September and October, which is historically a time of low flow in the river when natural saltwater intrusion occurs. The Fresh treatment plots receive regular additions of fresh river water. Treatment water is added during low tide to facilitate its infiltration into the soil, and all plots are inundated by astronomical tides at high tide. Response measurements include porewater chemistry, specifically concentrations of chloride, sulfate, sulfide, dissolved organic carbon (DOC), ammonium-N, nitrate/nitrite-N, dissolved reactive phosphorus, total phosphorus, total nitrogen, organic nitrogen, carbon:nitrogen (C:N) ratio, organic-carbon:organic-nitrogen ratio, and pH. Samples of source water were taken after collection (seawater, river water) or mixing (mixed seawater and river water in tanks) and analyzed for concentrations of dissolved reactive phosphorus, total phosphorus, ammonium-N, nitrate/nitrite-N, total nitrogen, organic nitrogen. Source water samples from 2016 and beyond also included measurements of dissolved organic carbon (DOC), carbon:nitrogen ratio, organic-carbon:organic-nitrogen ratio, chloride and sulfate.