Fate of terrestrial organic carbon and associated CO2 and CO emissions from two Southeast Asian estuaries.

Müller, D., Warneke, T., Rixen, T., Müller, M., Mujahid, A., Bange, Hermann W. and Notholt, J. (2016) Fate of terrestrial organic carbon and associated CO2 and CO emissions from two Southeast Asian estuaries. Open Access Biogeosciences (BG), 13 (3). pp. 691-705. DOI 10.5194/bg-13-691-2016.

[img]
Preview
Text
bg-13-691-2016.pdf - Published Version
Available under License Creative Commons: Attribution 3.0.

Download (531Kb) | Preview
[img]
Preview
Text
bg-13-691-2016-supplement.pdf - Supplemental Material
Available under License Creative Commons: Attribution 3.0.

Download (832Kb) | Preview

Supplementary data:

Abstract

Southeast Asian rivers convey large amounts of organic carbon, but little is known about the fate of this terrestrial material in estuaries. Although Southeast Asia is, by area, considered a hotspot of estuarine carbon dioxide (CO2) emissions, studies in this region are very scarce. We measured dissolved and particulate organic carbon, as well as CO2 partial pressures and carbon monoxide (CO) concentrations in two tropical estuaries in Sarawak, Malaysia, whose coastal area is covered by carbon-rich peatlands. We surveyed the estuaries of the rivers Lupar and Saribas during the wet and dry season, respectively. Carbon-to-nitrogen ratios suggest that dissolved organic matter (DOM) is largely of terrestrial origin. We found evidence that a large fraction of this carbon is respired. The median pCO(2) in the estuaries ranged between 640 and 5065 mu atm with little seasonal variation. CO2 fluxes were determined with a floating chamber and estimated to amount to 14-268 mol m(-2) yr(-1), which is high compared to other studies from tropical and subtropical sites. Estimates derived from a merely wind-driven turbulent diffusivity model were considerably lower, indicating that these models might be inappropriate in estuaries, where tidal currents and river discharge make an important contribution to the turbulence driving water-air gas exchange. Although an observed diurnal variability of CO concentrations suggested that CO was photochemically produced, the overall concentrations and fluxes were relatively moderate (0.4-1.3 nmol L-1 and 0.7-1.8 mmol m(-2) yr(-1)) if compared to published data for oceanic or upwelling systems. We attributed this to the large amounts of suspended matter (4-5004 mg L-1), limiting the light penetration depth and thereby inhibiting CO photoproduction. We concluded that estuaries in this region function as an efficient filter for terrestrial organic carbon and release large amounts of CO2 to the atmosphere. The Lupar and Saribas rivers deliver 0.3 +/- 0.2 TgC yr(-1) to the South China Sea as organic carbon and their mid-estuaries release approximately 0.4 +/- 0.2 TgC yr(-1) into the atmosphere as CO2.

Document Type: Article
Additional Information: WOS:000370973900005
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-13-691-2016
ISSN: 1726-4170
Projects: InGOS
Date Deposited: 18 Mar 2016 08:20
Last Modified: 01 Feb 2019 15:08
URI: http://oceanrep.geomar.de/id/eprint/31880

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...