title: In situ soft sediment nutrient enrichment: A unified approach to eutrophication field experiments.
abstract: Adding fertiliser to sediments is an established way of studying the effects of eutrophication but a lack of consistent methodology, reporting on enrichment levels, or guidance on application rates precludes rigorous synthesis and meta-analysis. We developed a simple enrichment technique then applied it to 28 sites across an intertidal sandflat. Fertiliser application rates of 150 and 600gNm(-2) resulted in pore water ammonium concentrations respectively 1-110 and 4-580×ambient, with greater elevations observed in deeper (5-7cm) than surface (0-2cm) sediments. These enrichment levels were similar to eutrophic estuaries and were maintained for at least seven weeks. The high between-site variability could be partially explained by the sedimentary environment and macrofaunal community (42%), but only at the high application rate. We suggest future enrichment studies should be conducted in situ across large environmental gradients to incorporate real world complexity and increase generality of conclusions.
authors.affiliation: School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. Electronic address: emilydouglas@outlook.com.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Douglas
authors.affiliation: School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
authors.forename: Conrad A
authors.initials: CA
authors.lastname: Pilditch
authors.affiliation: School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
authors.forename: Laura V
authors.initials: LV
authors.lastname: Hines
authors.affiliation: National Institute of Water and Atmospheric Research, P.O. Box 11-115, Hamilton 3251, New Zealand.
authors.forename: Casper
authors.initials: C
authors.lastname: Kraan
authors.affiliation: Institute of Marine Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Simon F
authors.initials: SF
authors.lastname: Thrush
mesh_terms: D064751:Ammonium Compounds / Q000032:analysis; D063366:Estuaries; D005068:Eutrophication; D005308:Fertilizers; D019015:Geologic Sediments / Q000032:analysis / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D005308:Fertilizers
keywords: Benthic; Enrichment method; Fertiliser; Intertidal; Macrofauna; Pore water