Coastal eutrophication as a driver of salt marsh loss.
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.
The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, USA. ldeegan@mbl.edu
Linda A
LA
Deegan
David Samuel
DS
Johnson
R Scott
RS
Warren
Bruce J
BJ
Peterson
John W
JW
Fleeger
Sergio
S
Fagherazzi
Wilfred M
WM
Wollheim
D000818:Animals; D018533:Biomass; D057965:Carbon Sequestration; D005068:Eutrophication / Q000502:physiology*; D005308:Fertilizers; D005502:Food; D005523:Food Supply; D009584:Nitrogen / Q000378:metabolism; D058458:Nitrogen Cycle; D012492:Salts; D053833:Wetlands
D005308:Fertilizers; D012492:Salts; D009584:Nitrogen