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Nitrous oxide and methane dynamics in a coral reef lagoon driven by pore water exchange: Insights from automated high‐frequency observations
Author(s) -
O'Reilly Chiara,
Santos Isaac R.,
Cyronak Tyler,
McMahon Ashly,
Maher Damien T.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl063126
Subject(s) - nitrous oxide , environmental science , methane , oceanography , denitrification , sink (geography) , nitrate , pore water pressure , carbon dioxide , environmental chemistry , dissolved organic carbon , groundwater , coral reef , seawater , reef , hydrology (agriculture) , nitrification , nitrogen , geology , chemistry , cartography , geotechnical engineering , organic chemistry , geography
Abstract Automated cavity ring down spectroscopy was used to make continuous measurements of dissolved methane, nitrous oxide, and carbon dioxide in a coral reef lagoon for 2 weeks (Heron Island, Great Barrier Reef). Radon ( 222 Rn) was used to trace the influence of tidally driven pore water exchange on greenhouse gas dynamics. Clear tidal variation was observed for CH 4 , which correlated to 222 Rn in lagoon waters. N 2 O correlated to 222 Rn during the day only, which appears to be a response to coupled nitrification‐denitrification in oxic sediments, fueled by nitrate derived from bird guano. The lagoon was a net source of CH 4 and N 2 O to the atmosphere and a sink for atmospheric CO 2 . The estimated pore water‐derived CH 4 and N 2 O fluxes were 3.2‐fold and 24.0‐fold greater than the fluxes to the atmosphere. Overall, pore water and/or groundwater exchange were the only important sources of CH 4 and major controls of N 2 O in the coral reef lagoon.