title: Are seagrass beds indicators of anthropogenic nutrient stress in the rocky intertidal?
abstract: It is well established that anthropogenic nutrient inputs harm estuarine seagrasses, but the influence of nutrients in rocky intertidal ecosystems is less clear. In this study, we investigated the effect of anthropogenic nutrient loading on Phyllospadix spp., a rocky intertidal seagrass, at local and regional scales. At sites along California, Washington, and Oregon, we demonstrated a significant, negative correlation of urban development and Phyllospadix bed thickness. These results were echoed locally along an urban gradient on the central California coast, where Phyllospadix shoot δ15N was negatively associated with Phyllospadix bed thickness, and experimentally, where nutrient additions in mesocosms reduced Phyllospadix shoot formation and increased epiphytic cover on Phyllospadix shoots. These findings provide evidence that coastal development can threaten rocky intertidal seagrasses through increased epiphytism. Considering that seagrasses provide vital ecosystem services, mitigating eutrophication and other factors associated with development in the rocky intertidal coastal zone should be a management priority.
authors.affiliation: Ecology & Evolutionary Biology Department, University of California, Santa Cruz, CA 95064, USA. Electronic address: shonig@ucsc.edu.
authors.forename: Susanna E
authors.initials: SE
authors.lastname: Honig
authors.affiliation: Ecology & Evolutionary Biology Department, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Brenna
authors.initials: B
authors.lastname: Mahoney
authors.affiliation: Ecology & Evolutionary Biology Department, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Jess S
authors.initials: JS
authors.lastname: Glanz
authors.affiliation: Ecology & Evolutionary Biology Department, University of California, Santa Cruz, CA 95064, USA; Nicholas School of the Environment, Duke Marine Laboratory, Duke University, Beaufort, NC 28516, USA.
authors.forename: Brent B
authors.initials: BB
authors.lastname: Hughes
mesh_terms: D002140:California; D017753:Ecosystem; D004777:Environment; D005068:Eutrophication; D009587:Nitrogen Isotopes / Q000378:metabolism; D009922:Oregon; D014507:Urbanization; D014861:Washington; D035962:Zosteraceae / Q000502:physiology*
chemical_list: D009587:Nitrogen Isotopes
keywords: Coastal development; Epiphyte; Foundation species; Nutrients; Phyllospadix; Stable isotopes