title: Broad-scale patterns of tissue-δ15N and tissue-N indices in frondose Ulva spp.; developing a national baseline indicator of nitrogen-loading for coastal New Zealand.
abstract: A survey of tissue-δ(15)N and tissue-N values in the green macroalga, Ulva, was conducted around the coast of New Zealand to determine if these indices could be used as indicators of anthropogenic nutrient loading in coastal waters. In addition, data from four case studies showed temporal and spatial responses of tissue-δ(15)N and tissue-N in Ulva to significant terrestrial nutrient inputs. Tissue-δ(15)N in Ulva from 'natural' exposed coastal sites showed a relatively narrow baseline range of values (6.6±0.1-8.8±0.1‰) in both summer and winter that was consistent throughout New Zealand. Departures in Ulva tissue-δ(15)N ratios outside this range, particularly when coupled with high (>3.1%) tissue-N values, indicate significant contributions of terrestrially-derived nitrogen to coastal seawater. We note that tissue-N content is also affected by exposure, light and season; however provided such factors are taken into account Ulva can be a cost-effective indicator of relative changes in both source and amount of nitrogen-loading.
authors.affiliation: National Institute of Water & Atmospheric Research Limited (NIWA), Mahanga Bay Aquaculture Research Facility, Private Bag 14901, Wellington, New Zealand. n.barr@niwa.co.nz
authors.forename: Neill G
authors.initials: NG
authors.lastname: Barr
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Dudley
authors.forename: Karyne M
authors.initials: KM
authors.lastname: Rogers
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Cornelisen
mesh_terms: D009520:New Zealand; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism* / Q000592:standards; D009587:Nitrogen Isotopes / Q000032:analysis / Q000378:metabolism; D012623:Seawater / Q000737:chemistry; D044445:Ulva / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism* / Q000592:standards
chemical_list: D009587:Nitrogen Isotopes; D014874:Water Pollutants, Chemical; D009584:Nitrogen