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Land use drives nitrous oxide dynamics in estuaries on regional and global scales
Author(s) -
Reading Michael J.,
Tait Douglas R.,
Maher Damien T.,
Jeffrey Luke C.,
Looman Arun,
Holloway Ceylena,
Shishaye Haile A.,
Barron Summer,
Santos Isaac R.
Publication year - 2020
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11426
Subject(s) - estuary , environmental science , hydrology (agriculture) , nitrous oxide , nitrate , denitrification , greenhouse gas , mangrove , saturation (graph theory) , nitrogen , ecology , chemistry , biology , geotechnical engineering , engineering , mathematics , organic chemistry , combinatorics
Urban and agricultural development of coastal catchments is known to increase dissolved nitrogen inputs into estuaries; however, much less is known about how land use influences the production of the powerful greenhouse gas nitrous oxide (N 2 O). Here, we assess dissolved N 2 O dynamics in four nearby estuaries across a regional land use gradient and summarize the literature to put the observations into global perspective. During summer dry conditions, N 2 O saturation ranged from 131.4% ± 45.0% in the most pristine system (28% modified) to 198.6% ± 52.3% within the most modified urban system (91% modified). The N 2 O saturation in the wetter winter campaign was higher and more variable than the summer dry campaign (range 84.7–677.7%) likely due to direct transport of N 2 O into the estuaries from catchment runoff and/or produced through denitrification fueled by high nitrate inputs. During both seasons, N 2 O was lowest in areas adjacent to fringing mangroves and highest in upstream fresh/saltwater mixing areas. Coupling our results with previously published N 2 O data from 50 estuarine systems worldwide revealed that estuarine N 2 O increases concomitantly with catchment modification, dissolved inorganic nitrogen availability, and decreasing oxygen concentrations. Based on these results, a 1% increase in anthropogenic modification to global catchments (i.e., agricultural development and/or urbanization) may increase estuarine N 2 O saturation by 2.6% ± 1.2%. These findings indicate that future estuarine N 2 O emissions are likely to increase as anthropogenic modification of coastal catchments intensifies.