title: Multi-year persistence of beach habitat degradation from nourishment using coarse shelly sediments.
abstract: Beach nourishment is increasingly used to protect public beach amenity and coastal property from erosion and storm damage. Where beach nourishment uses fill sediments that differ in sedimentology from native beach sands, press disturbances to sandy beach invertebrates and their ecosystem services can occur. How long impacts persist is, however, unclear because monitoring after nourishment typically only extends for several months. Here, monitoring was extended for 3-4 years following each of two spatially separated, replicate nourishment projects using unnaturally coarse sediments. Following both fill events, the contribution to beach sediments of gravel-sized particles and shell fragments was enhanced, and although diminishing through time, remained elevated as compared to control sites at the end of 3-4 years of monitoring, including in the low intertidal and swash zones, where benthic macroinvertebrates concentrate. Consequently, two infaunal invertebrates, haustoriid amphipods and Donax spp., exhibited suppressed densities over the entire post-nourishment period of 3-4 years. Emerita talpoida, by contrast, exhibited lower densities on nourished than control beaches only in the early summer of the first and second years and polychaetes exhibited little response to nourishment. The overall impact to invertebrates of nourishment was matched by multi-year reductions in abundances of their predators. Ghost crab abundances were suppressed on nourished beaches with impacts disappearing only by the fourth summer. Counts of foraging shorebirds were depressed for 4 years after the first project and 2 years after the second project. Our results challenge the view that beach nourishment is environmentally benign by demonstrating that application of unnaturally coarse and shelly sediments can serve as a press disturbance to degrade the beach habitat and its trophic services to shorebirds for 2-4 years. Recognizing that recovery following nourishment can be slow, studies that monitor impacts for only several months are inadequate.
authors.affiliation: University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557, USA; Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA. Electronic address: cpeters@email.unc.edu.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Peterson
authors.affiliation: Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia. Electronic address: melanie.bishop@mq.edu.au.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Bishop
authors.affiliation: University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557, USA; Institute for Coastal Research, Vancouver Island University, 900 Fifth Street, Nanaimo, BC V9R 5S5, Canada. Electronic address: lmdanna@gmail.com.
authors.forename: Linda M
authors.initials: LM
authors.lastname: D'Anna
authors.affiliation: University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 28557, USA; Northwest Indian Fisheries Commission, 6730 Martin Way E., Olympia, WA 98516, USA. Electronic address: galen.a.johns@gmail.com.
authors.forename: Galen A
authors.initials: GA
authors.lastname: Johnson
mesh_terms: D033304:Amphipoda; D000818:Animals; D001493:Bathing Beaches / Q000706:statistics & numerical data; D049872:Bivalvia; D003386:Brachyura; D003247:Conservation of Natural Resources / Q000379:methods*; D017753:Ecosystem; D052918:Environmental Restoration and Remediation / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry; D007448:Invertebrates / Q000254:growth & development*; D010316:Particle Size
keywords: Beach erosion; Beach nourishment; Ecological recovery; Impact assessment; Press response