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Marine Ecology Progress Series

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MEPS 528:117-126 (2015)  -  DOI:

Nitrogen dynamics on Guam as revealed by the seagrass Enhalus acoroides

K. Pinkerton1, D. M. Baker2, M. R. Cuddy1, L. J. Raymundo3, K. A. Meyer1, K. Kim1,*

1Department of Environmental Science, American University, 4400 Massachusetts Ave NW, Washington, DC 20016, USA
2School of Biological Sciences & Department of Earth Science, University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong SAR
3University of Guam Marine Laboratory, UOG Station, Mangilao, GU 96923, USA
*Corresponding author:

ABSTRACT: Seagrasses are critical to productive coastal ecosystems but are endangered and poorly studied, especially in the tropical Indo-Pacific. A key local threat is the increasing anthropogenic input of nitrogen (N). We hypothesized that such N eutrophication is occurring on Guam, the largest and most populated of the Northern Mariana Islands. We examined the seagrass Enhalus acoroides over 5 years and applied stable isotope analysis to document N dynamics and impacts. Although δ15N values indicated that sewage-derived N was the dominant source, the δ15N values were unrelated to either seagrass cover or growth rate. Strong relationships between seagrass δ15N values and both distance to the nearest source of N inputs and population density of adjacent municipalities suggest that N inputs are highly localized. Although there was no evidence of a negative impact of sewage-derived N inputs on seagrasses, this study provides a useful reference for evaluating mitigation efforts and for tracking the effect of increasing anthropogenic eutrophication on Guam.

KEY WORDS:  Seagrasses · Tropical Indo-Pacific · Stable isotope analysis · Eutrophication

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Cite this article as: Pinkerton K, Baker DM, Cuddy MR, Raymundo LJ, Meyer KA, Kim K (2015) Nitrogen dynamics on Guam as revealed by the seagrass Enhalus acoroides. Mar Ecol Prog Ser 528:117-126.

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