title: Nutrient loading alters the performance of key nutrient exchange mutualisms.
abstract: Nutrient exchange mutualisms between phototrophs and heterotrophs, such as plants and mycorrhizal fungi or symbiotic algae and corals, underpin the functioning of many ecosystems. These relationships structure communities, promote biodiversity and help maintain food security. Nutrient loading may destabilise these mutualisms by altering the costs and benefits each partner incurs from interacting. Using meta-analyses, we show a near ubiquitous decoupling in mutualism performance across terrestrial and marine environments in which phototrophs benefit from enrichment at the expense of their heterotrophic partners. Importantly, heterotroph identity, their dependence on phototroph-derived C and the type of nutrient enrichment (e.g. nitrogen vs. phosphorus) mediated the responses of different mutualisms to enrichment. Nutrient-driven changes in mutualism performance may alter community organisation and ecosystem processes and increase costs of food production. Consequently, the decoupling of nutrient exchange mutualisms via alterations of the world's nitrogen and phosphorus cycles may represent an emerging threat of global change.
authors.affiliation: Department of Biology, Florida International University, Miami, FL, 33199, USA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Shantz
authors.affiliation: Department of Biology, Florida International University, Miami, FL, 33199, USA.|Department of Biology, Colorado State University, Fort Collins, CO, 80523, USA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Lemoine
authors.affiliation: Department of Biology, Florida International University, Miami, FL, 33199, USA.|Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, 93106, USA.
authors.forename: Deron E
authors.initials: DE
authors.lastname: Burkepile
mesh_terms: D057486:Carbon Cycle; D052836:Heterotrophic Processes; D058458:Nitrogen Cycle; D010758:Phosphorus / Q000378:metabolism; D052817:Phototrophic Processes; D013559:Symbiosis
chemical_list: D010758:Phosphorus
keywords: Coral; Symbiodinium; eutrophication; mutualism; mycorrhizae; nutrient loading; nutrification; parasitism; rhizobia; symbiosis