Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo
Estuaries are sources of nitrous oxide (N<sub>2</sub>O) and methane (CH<sub>4</sub>) to the atmosphere. However, our present knowledge of N<sub>2</sub>O and CH<sub>4</sub> emissions from estuaries in the tropics is very limited because data are scarce....
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-04-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/2415/2016/bg-13-2415-2016.pdf |
| _version_ | 1819142150153043968 |
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| author | D. Müller H. W. Bange T. Warneke T. Rixen M. Müller A. Mujahid J. Notholt |
| author_facet | D. Müller H. W. Bange T. Warneke T. Rixen M. Müller A. Mujahid J. Notholt |
| author_sort | D. Müller |
| collection | DOAJ |
| description | Estuaries are sources of nitrous oxide (N<sub>2</sub>O) and methane (CH<sub>4</sub>) to
the atmosphere. However, our present knowledge of N<sub>2</sub>O and CH<sub>4</sub>
emissions from estuaries in the tropics is very limited because data are
scarce. In this study, we present first measurements of dissolved N<sub>2</sub>O
and CH<sub>4</sub> from two estuaries in a peat-dominated region of northwestern
Borneo. Two campaigns (during the dry season in June 2013 and during the wet
season in March 2014) were conducted in the estuaries of the Lupar and
Saribas rivers. Median N<sub>2</sub>O concentrations ranged between 7.2 and
12.3 nmol L<sup>−1</sup> and were higher in the marine end-member
(13.0 ± 7.0 nmol L<sup>−1</sup>). CH<sub>4</sub> concentrations were low in the
coastal ocean (3.6 ± 0.2 nmol L<sup>−1</sup>) and higher in the estuaries
(medians between 10.6 and 64.0 nmol L<sup>−1</sup>). The respiration of abundant
organic matter and presumably anthropogenic input caused slight
eutrophication, which did not lead to hypoxia or enhanced N<sub>2</sub>O
concentrations, however. Generally, N<sub>2</sub>O concentrations were not related
to dissolved inorganic nitrogen concentrations. Thus, the use of an emission
factor for the calculation of N<sub>2</sub>O emissions from the inorganic nitrogen
load leads to an overestimation of the flux from the Lupar and Saribas
estuaries. N<sub>2</sub>O was negatively correlated with salinity during the dry
season, which suggests a riverine source. In contrast, N<sub>2</sub>O
concentrations during the wet season were not correlated with salinity but
locally enhanced within the estuaries, implying that there were additional
estuarine sources during the wet (i.e., monsoon) season. Estuarine CH<sub>4</sub>
distributions were not driven by freshwater input but rather by tidal
variations. Both N<sub>2</sub>O and CH<sub>4</sub> concentrations were more variable
during the wet season. We infer that the wet season dominates the variability
of the N<sub>2</sub>O and CH<sub>4</sub> concentrations and subsequent emissions from
tropical estuaries. Thus, we speculate that any changes in the Southeast
Asian monsoon system will lead to changes in the N<sub>2</sub>O and CH<sub>4</sub>
emissions from these systems. We also suggest that the ongoing cultivation of
peat soil in Borneo is likely to increase N<sub>2</sub>O emissions from these
estuaries, while the effect on CH<sub>4</sub> remains uncertain. |
| first_indexed | 2024-12-22T12:05:46Z |
| format | Article |
| id | doaj.art-d1fe3e678485461e922e650ed8f10ec8 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-22T12:05:46Z |
| publishDate | 2016-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-d1fe3e678485461e922e650ed8f10ec82022-12-21T18:26:27ZengCopernicus PublicationsBiogeosciences1726-41701726-41892016-04-011382415242810.5194/bg-13-2415-2016Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern BorneoD. Müller0H. W. Bange1T. Warneke2T. Rixen3M. Müller4A. Mujahid5J. Notholt6Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, GermanyInstitute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, GermanyLeibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, GermanySwinburne University of Technology, Faculty of Engineering, Computing and Science, Jalan Simpang Tiga, 93350 Kuching, Sarawak, MalaysiaDepartment of Aquatic Science, Faculty of Resource Science & Technology, University Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, MalaysiaInstitute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, GermanyEstuaries are sources of nitrous oxide (N<sub>2</sub>O) and methane (CH<sub>4</sub>) to the atmosphere. However, our present knowledge of N<sub>2</sub>O and CH<sub>4</sub> emissions from estuaries in the tropics is very limited because data are scarce. In this study, we present first measurements of dissolved N<sub>2</sub>O and CH<sub>4</sub> from two estuaries in a peat-dominated region of northwestern Borneo. Two campaigns (during the dry season in June 2013 and during the wet season in March 2014) were conducted in the estuaries of the Lupar and Saribas rivers. Median N<sub>2</sub>O concentrations ranged between 7.2 and 12.3 nmol L<sup>−1</sup> and were higher in the marine end-member (13.0 ± 7.0 nmol L<sup>−1</sup>). CH<sub>4</sub> concentrations were low in the coastal ocean (3.6 ± 0.2 nmol L<sup>−1</sup>) and higher in the estuaries (medians between 10.6 and 64.0 nmol L<sup>−1</sup>). The respiration of abundant organic matter and presumably anthropogenic input caused slight eutrophication, which did not lead to hypoxia or enhanced N<sub>2</sub>O concentrations, however. Generally, N<sub>2</sub>O concentrations were not related to dissolved inorganic nitrogen concentrations. Thus, the use of an emission factor for the calculation of N<sub>2</sub>O emissions from the inorganic nitrogen load leads to an overestimation of the flux from the Lupar and Saribas estuaries. N<sub>2</sub>O was negatively correlated with salinity during the dry season, which suggests a riverine source. In contrast, N<sub>2</sub>O concentrations during the wet season were not correlated with salinity but locally enhanced within the estuaries, implying that there were additional estuarine sources during the wet (i.e., monsoon) season. Estuarine CH<sub>4</sub> distributions were not driven by freshwater input but rather by tidal variations. Both N<sub>2</sub>O and CH<sub>4</sub> concentrations were more variable during the wet season. We infer that the wet season dominates the variability of the N<sub>2</sub>O and CH<sub>4</sub> concentrations and subsequent emissions from tropical estuaries. Thus, we speculate that any changes in the Southeast Asian monsoon system will lead to changes in the N<sub>2</sub>O and CH<sub>4</sub> emissions from these systems. We also suggest that the ongoing cultivation of peat soil in Borneo is likely to increase N<sub>2</sub>O emissions from these estuaries, while the effect on CH<sub>4</sub> remains uncertain.http://www.biogeosciences.net/13/2415/2016/bg-13-2415-2016.pdf |
| spellingShingle | D. Müller H. W. Bange T. Warneke T. Rixen M. Müller A. Mujahid J. Notholt Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo Biogeosciences |
| title | Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo |
| title_full | Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo |
| title_fullStr | Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo |
| title_full_unstemmed | Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo |
| title_short | Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo |
| title_sort | nitrous oxide and methane in two tropical estuaries in a peat dominated region of northwestern borneo |
| url | http://www.biogeosciences.net/13/2415/2016/bg-13-2415-2016.pdf |
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