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Published (Version of record)CC BY-NC V4.0, Open Access
Published (Version of record)CC BY-NC V4.0, Open
Journal article
Linking Transpiration to Reef Nitrogen Supply on a Tropical Coral Island
Journal of geophysical research. Biogeosciences, Vol.129(2), e2023JG007413
02/2024
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Abstract
Coral reef islands are biodiversity hotspots with high conservation value, but we have a poor understanding of how island vegetation, through transpiration, influences groundwater nutrient supply to adjacent reef systems. Here we combine stable isotope tracing, geophysical surveys, and satellite analysis to unravel the links between transpiration and the discharge of groundwater nitrate to the waters surrounding a coral reef island (Lady Elliot Island in the Great Barrier Reef). Over a 2-year study period (2020–2021) there was a net loss of freshwater from the island, that is, evapotranspiration (ET) exceeded rainfall, largely caused by high rates of transpiration (73% of ET). Transpiration was higher in forested areas, and groundwater salinity appeared to be higher there. By tracing the nitrogen stable isotope signature of groundwater nitrate into reef organism tissue we were able to map groundwater nitrogen discharge spatially and temporally. Groundwater nitrogen discharge was focussed on one side of the island and did not vary seasonally as expected, despite reduced rainfall and seabird guano inputs over the austral winter/spring. Based on our results, we propose that transpiration by island vegetation slows groundwater flow and concentrates nitrate in the groundwater being released to the surrounding reef system. High concentrations of nitrate in groundwater (up to 27 mmol L−) were observed on Lady Elliot Island and these seem to have increased since 2014, but further work is required to understand if this is a normal scenario for tropical coral islands or the result of the islands' revegetation program.
Details
- Title
- Linking Transpiration to Reef Nitrogen Supply on a Tropical Coral Island
- Creators
- Dirk V. Erler - Southern Cross UniversityChristine L. Dudgeon - University of the Sunshine CoastAsia O. Armstrong - University of the Sunshine CoastEddie W. Banks - Flinders UniversityOrlando Ramirez-Valle - The University of Texas at El PasoHugo A. Gutiérrez-Jurado - The University of Texas at El PasoBen L. Gilby - University of the Sunshine CoastKathy A. Townsend - University of the Sunshine Coast
- Publication Details
- Journal of geophysical research. Biogeosciences, Vol.129(2), e2023JG007413
- Publisher
- Wiley-Blackwell Publishing, Inc.
- Number of pages
- 16
- Grant note
- Fitzgerald Family Foundation Great Barrier Reef Foundation Lendlease
- Identifiers
- 991013169399802368
- Copyright
- © 2024 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License. Open access publishing facilitated by Southern Cross University, as part of the Wiley - Southern Cross University agreement via the Council of Australian University Librarians.
- Academic Unit
- Faculty of Science and Engineering; Science
- Language
- English
- Resource Type
- Journal article