Reference : Carbon biogeochemistry of the Betsiboka Estuary (north-western Madagascar)
Scientific journals : Article
Life sciences : Aquatic sciences & oceanology
Carbon biogeochemistry of the Betsiboka Estuary (north-western Madagascar)
Ralison, Olivier Harifidy [Vrije Universiteit Brussel > Department of Analytical and Environmental Chemistry]
Borges, Alberto mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique >]
Dehairs, Frank [Vrije Universiteit Brussel > Department of Analytical and Environmental Chemistry]
Bouillon, Steven [> > > >]
Organic Geochemistry
Pergamon Press - An Imprint of Elsevier Science
Yes (verified by ORBi)
United Kingdom
[en] Madagascar’s largest estuary (Betsiboka) was sampled along the salinity gradient during
the dry season to document the distribution and sources of particulate and dissolved
organic carbon (POC, DOC) as well as dissolved inorganic carbon (DIC). The Betsiboka
was characterized by a relatively high suspended matter load, and in line with this, low
DOC/POC ratios ( 0.4–2.5). The partial pressure of CO2 (pCO2) was generally above atmospheric
equilibrium (270–1530 ppm), but relatively low in comparison to other tropical
and subtropical estuaries, resulting in low average CO2 emission to the atmosphere
(9.1 ± 14.2 mmol m 2 d 1). Despite the fact that C4 vegetation is reported to cover >80%
of the catchment area, stable isotope data on DOC and POC suggest that C4 derived material
comprises only 30% of both pools in the freshwater zone, increasing to 60–70% and
50–60%, respectively, in the oligohaline zone due to additional lateral inputs. Sediments
from intertidal mangroves in the estuary showed low organic carbon concentrations
(<1%) and d13C values (average 19.8‰) consistent with important inputs of riverine
imported C4 material. This contribution was reflected in d13C signatures of bacterial
phospholipid derived fatty acids (i + a15:0), suggesting the potential importance of terrestrial
organic matter sources for mineralization and secondary production in coastal

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