Identifying nitrogen sources to thermal tide pools in Kapoho, Hawai'i, U.S.A, using a multi-stable isotope approach. Issue 1 (15th February 2016)

• Record Type: Journal Article
• Authors: Wiegner, Tracy N.; Mokiao-Lee, Ambyr U.; Johnson, Erik E.
• Is Part Of: Marine pollution bulletin. Volume 103:Issue 1/2(2016:Feb.)
• Page Start: 63
• Page End: 71
• Publication Date: 2016-02-15
• Subjects: Coastal waters -- Fertilizers -- Macroalgae -- Sewage -- Stable isotopes -- Water quality; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2015.12.046
• Languages: English
• ISSNs: 0025-326X

Abstract

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. Highlights: Multi-stable isotope approach successfully identified N sources to tide pools. NO3-isotopes identified agriculture and groundwater as key N sources, not sewage. δ 15 N indicated tide pool algae used N from agricultural soils. Mixing model apportioned contributions of N sources to tide pools. Agricultural soils were largest anthropogenic N source to tide pools.