Wetland restoration is becoming an important tool to reverse coastal degradation and enhance the provisioning of ecosystem services. However, the capacity of restored coastal wetlands to provide multiple ecosystem services can be limited due to land-use legacies and rising salinities downstream. In the southeast coastal plain of the US changes in droughts and storms can often lead to temporary increases in salinity. Here we use seven years of surface water and soil solution chemistry from a large (440 ha) restored wetland to examine how fertilizer legacy, storms, and drought affect nutrient and carbon export. We compared the restored wetland to an active agricultural field and two mature forested wetlands. We also conducted a field salt addition experiment in the restored wetland to examine changes in nutrient, algal biomass, and dissolved organic carbon (DOC) concentrations in surface water.
Our results showed that both surface and soil water chemistry nutrients in the restored wetland have declined since the initial reflooding of the site. However, both storms and drought-induced saltwater incursion can lead to increased nutrient export. In contrast, dissolved organic carbon export declined with drought and saltwater incursion. The experimental field salt addition showed increased nitrogen and chlorophyll a concentrations and that up to 30% of DOC can be transformed into particulate organic carbon through flocculation. Our results suggest that constraints on recovery of water quality benefits from past agricultural land uses are a temporary phenomenon, but one that in the face of changing storm frequency and increasing salinities should be considered when determining the regulatory duration of monitoring after wetland restoration.