title: Temporal variability of CO₂ fluxes at the sediment-air interface in mangroves (New Caledonia).
abstract: Carbon budgets in mangrove forests are uncertain mainly due to the lack of data concerning carbon export in dissolved and gaseous forms. Temporal variability of in situ CO2 fluxes was investigated at the sediment-air interface in different seasons in different mangrove stands in a semi-arid climate. Fluxes were measured using dynamic closed incubation chambers (transparent and opaque) connected to an infra-red gas analyzer. Microclimatic conditions and chl-a contents of surface sediments were determined. Over all mangrove stands, CO2 fluxes on intact sediments were relatively low, ranging from -3.93 to 8.85 mmolCO₂·m(-2)·h(-1) in the light and in the dark, respectively. Changes in the fluxes over time appeared to depend to a great extent on the development of the biofilm at the sediment surface. We suggest that in intact sediments and in the dark, CO2 fluxes measured at the sediment-air interface rather reflect the metabolism of benthic organisms than sediment respiration (heterotrophic and autotrophic). However, without the biofilm, sediment water content and air temperature were main drivers of seasonal differences in CO2 fluxes, and their influence differed depending on the intertidal location of the stand. After removal of the biofilm, Q10 values in the Avicennia and the Rhizophora stands were 1.84 and 2.1, respectively, revealing the sensitivity of mangrove sediments to an increase in temperature. This study provides evidence that, if the influence of the biofilm is not taken into account, the in situ CO2 emission data currently used to calculate the budget will lead to underestimation of CO2 production linked to heterotrophic respiration fueled by organic matter detritus from the mangrove.
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR 7590, UR 206, BP A5, 98848 Nouméa, New Caledonia; Université de la Nouvelle-Calédonie, PPME, EA 3325, BP R4, 98851 Noumea, New Caledonia.
authors.forename: Audrey
authors.initials: A
authors.lastname: Leopold
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR 7590, UR 206, BP A5, 98848 Nouméa, New Caledonia. Electronic address: cyril.marchand@ird.fr.
authors.forename: Cyril
authors.initials: C
authors.lastname: Marchand
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR 7590, UR 206, BP A5, 98848 Nouméa, New Caledonia.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Deborde
authors.affiliation: Université de la Nouvelle-Calédonie, PPME, EA 3325, BP R4, 98851 Noumea, New Caledonia.
authors.forename: Michel
authors.initials: M
authors.lastname: Allenbach
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D032407:Avicennia; D002245:Carbon Dioxide / Q000032:analysis*; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D009510:New Caledonia; D014873:Water Pollutants / Q000032:analysis*; D053833:Wetlands
chemical_list: D000393:Air Pollutants; D014873:Water Pollutants; D002245:Carbon Dioxide
keywords: Biofilm; In situ sediment CO(2) fluxes; Mangrove; New Caledonia; Seasonal variation