Coastal Eutrophication as a Driver of Salt Marsh Loss

Linda A. Deegan, David Samuel Johnson, Scott R. Warren, Bruce J. Peterson, John W. Fleeger, Sergio Fagherazzi, Wilfred M. Wollheim
Created: 2/25/2015 -


Salt marshes are highly productive coastal wetlands that provide important ecosystem services such as storm protection for coastal cities, nutrient removal and carbon sequestration. Despite protective measures, however, worldwide losses of these ecosystems have accelerated in recent decades. Here we present data from a nine-year whole-ecosystem nutrient-enrichment experiment. Our study demonstrates that nutrient enrichment, a global problem for coastal ecosystems, can be a driver of salt marsh loss. We show that nutrient levels commonly associated with coastal eutrophication increased above-ground leaf biomass, decreased the dense, below-ground biomass of bank-stabilizing roots, and increased microbial decomposition of organic matter. Alterations in these key ecosystem properties reduced geomorphic stability, resulting in creek-bank collapse with significant areas of creek-bank marsh converted to unvegetated mud. This pattern of marsh loss parallels observations for anthropogenically nutrient-enriched marshes worldwide, with creek-edge and bay-edge marsh evolving into mudflats and wider creeks. Our work suggests that current nutrient loading rates to many coastal ecosystems have overwhelmed the capacity of marshes to remove nitrogen without deleterious effects. Projected increases in nitrogen flux to the coast, related to increased fertilizer use required to feed an expanding human population, may rapidly result in a coastal landscape with less marsh, which would reduce the capacity of coastal regions to provide important ecological and economic services.

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The Northeast Climate Science Center (NECSC) is part of a federal network of eight Climate Science Centers created to provide scientific information, tools, and techniques that managers and other parties interested in land, water, wildlife and culturalresources can use to anticipate, monitor, and adapt to climate change.


Type of Adaptation Action/Strategy
Natural Resource Management / Conservation
Reduce local climate or related change
Reduce non-climate stressors
Capacity Building
Conduct / Gather additional research, data, and products
Target Climate Changes and Impacts
Flow patterns
Habitat extent