title: Identifying nitrogen sources to thermal tide pools in Kapoho, Hawai'i, U.S.A, using a multi-stable isotope approach.
abstract: Nitrogen (N) enrichment often results in coastal eutrophication, even in remote areas like Hawai'i. Therefore, determining N sources to coastal waters is important for their management. This study identified N sources to tide pools in Kapoho, Hawai'i, and determined their relative importance using three stable isotopes (δ(15)N, δ(18)O, δ(11)B). Surface waters and macroalgal tissues were collected along 100-m onshore-offshore transects in areas of high groundwater input for three months at low tide. Water samples from possible N sources were also collected. Mixing model output, along with macroalgal δ(15)N values, indicated that agriculture soil (34%) was the largest anthropogenic N source followed by sewage (27%). These findings suggest that more effective fertilizer application techniques and upgrading sewage treatment systems can minimize N leaching into groundwater. Overall, our multi-stable isotope approach for identifying N sources was successful and may be useful in other coastal waters.
authors.affiliation: Marine Science Department, University of Hawai'i at Hilo, 200 W. Kawili St., Hilo, HI 96720, USA. Electronic address: wiegner@hawaii.edu.
authors.forename: Tracy N
authors.initials: TN
authors.lastname: Wiegner
authors.affiliation: Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i at Hilo, 200 W. Kawili St., Hilo, HI 96720, USA. Electronic address: ambyrmlee@gmail.com.
authors.forename: Ambyr U
authors.initials: AU
authors.lastname: Mokiao-Lee
authors.affiliation: Tropical Conservation Biology and Environmental Science Graduate Program, University of Hawai'i at Hilo, 200 W. Kawili St., Hilo, HI 96720, USA. Electronic address: erikej@hawaii.edu.
authors.forename: Erik E
authors.initials: EE
authors.lastname: Johnson
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring / Q000379:methods*; D005068:Eutrophication; D005308:Fertilizers / Q000032:analysis; D060587:Groundwater / Q000737:chemistry; D006254:Hawaii; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis / Q000737:chemistry; D012722:Sewage / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D005308:Fertilizers; D009587:Nitrogen Isotopes; D012722:Sewage; D012987:Soil; D014874:Water Pollutants, Chemical; D009584:Nitrogen
keywords: Coastal waters; Fertilizers; Macroalgae; Sewage; Stable isotopes; Water quality