Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 9063
Title: Fertilizer legacies meet saltwater incursion: challenges and constraints for coastal plain wetland restoration
Author: Marcelo Ardón, Ashley M. Helton, M. D. Scheuerell, Emily S. Bernhardt
Publication Year: 2017
Journal: Elementa: Science of the Anthropocene
Volume: 5
Pages: 41
DOI: 10.1525/elementa.236

Coastal wetland restoration is an important tool for climate change adaptation and excess nutrient runoff mitigation. However, the capacity of restored coastal wetlands to provide multiple ecosystem services is limited by stressors such as excess nutrients from upstream agricultural fields, high nutrient legacies on-site, and rising salinities downstream. The effects of these stressors are exacerbated by an accelerating hydrologic cycle, expected to cause longer droughts punctuated by more severe storms. We used seven years of surface and soil solution water chemistry from a large (440 ha) restored wetland to examine how fertilizer legacy, changes in hydrology, and drought-induced salinization affect dissolved nutrient and carbon concentrations. To better understand the recovery trajectory of the restored wetland, we also sampled an active agricultural field and two mature forested wetlands. Our results show that nitrogen and phosphorus concentrations in soil solution were 2-10 times higher in the restored wetland compared to two mature forested wetlands, presumably due to fertilizer legacy. Despite the elevated nutrients, the restored wetland attenuated N and P pulses from an upstream agricultural field. Both N and P concentrations in surface water have decreased since the initial flooding. Drought-induced salinization increased release of inorganic N but not P from the restored wetland. Our results suggest that high nutrient concentrations due to past agricultural land uses are a temporary problem, but one that in the face of changing precipitation and increasing salinities should be considered when determining the regulatory length of monitoring post restoration. If restored wetlands are to be used to ameliorate nutrient runoff from coastal agricultural watersheds and as a climate change adaptation tool, we need a better understanding of interactions between changing hydrologic regimes, salinity, and land-use legacies.


This manuscript describes how long-term fertilizer in ajacent to coastal wetlands can have last effects on biogeochemical cycles.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Develop effective and efficient habitat restoration and conservation techniques.