title: A keystone mutualism underpins resilience of a coastal ecosystem to drought.
abstract: Droughts are increasing in severity and frequency, yet the mechanisms that strengthen ecosystem resilience to this stress remain poorly understood. Here, we test whether positive interactions in the form of a mutualism between mussels and dominant cordgrass in salt marshes enhance ecosystem resistance to and recovery from drought. Surveys spanning 250 km of southeastern US coastline reveal spatially dispersed mussel mounds increased cordgrass survival during severe drought by 5- to 25-times. Surveys and mussel addition experiments indicate this positive effect of mussels on cordgrass was due to mounds enhancing water storage and reducing soil salinity stress. Observations and models then demonstrate that surviving cordgrass patches associated with mussels function as nuclei for vegetative re-growth and, despite covering only 0.1-12% of die-offs, markedly shorten marsh recovery periods. These results indicate that mutualisms, in supporting stress-resistant patches, can play a disproportionately large, keystone role in enhancing ecosystem resilience to climatic extremes.
authors.affiliation: Department of Environmental Engineering Sciences, Engineering School for Sustainable Infrastructure and Environment, University of Florida, PO Box 116580, Gainesville, Florida 32611, USA.
authors.forename: Christine
authors.identifier: http://orcid.org/0000-0002-6669-5269
authors.initials: C
authors.lastname: Angelini
authors.affiliation: Department of Biosciences, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
authors.forename: John N
authors.initials: JN
authors.lastname: Griffin
authors.affiliation: Department of Estuarine and Delta Systems (EDS), Royal Netherlands Institute for Sea Research and Utrecht University (NIOZ-Yerseke), Postbus 140, Yerseke 4400 AC, The Netherlands.|Conservation Ecology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, PO Box 11103, Groningen 9700 CC, The Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: van de Koppel
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, Heyendaalsweg 135, Nijmegen 6525 AJ, The Netherlands.
authors.forename: Leon P M
authors.initials: LPM
authors.lastname: Lamers
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, Heyendaalsweg 135, Nijmegen 6525 AJ, The Netherlands.
authors.forename: Alfons J P
authors.initials: AJP
authors.lastname: Smolders
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, Heyendaalsweg 135, Nijmegen 6525 AJ, The Netherlands.
authors.forename: Marlous
authors.initials: M
authors.lastname: Derksen-Hooijberg
authors.affiliation: Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, Heyendaalsweg 135, Nijmegen 6525 AJ, The Netherlands.
authors.forename: Tjisse
authors.initials: T
authors.lastname: van der Heide
authors.affiliation: Department of Marine Science and Conservation, Nicolas School of the Environment, Duke University, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Silliman
mesh_terms: D000818:Animals; D018533:Biomass; D049872:Bivalvia / Q000502:physiology; D055864:Droughts; D017753:Ecosystem; D006109:Poaceae / Q000502:physiology; D054712:Salinity; D013312:Stress, Physiological; D013559:Symbiosis