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Impact of climatic changes on organic carbon dynamic in wet tropical watersheds of Guadeloupe (FWI).

Abstract : To better understand the global carbon cycle and the impact of changing climatic conditions, it is important to constrain the different sources, sinks and fluxes of carbon. The soil organic matter (≈ 1500 Gt [1]) is a major pool of carbon at the Earth surface, it is therefore important to understand its dynamic. If the increase of the frequency and/or intensity of extreme meteorological events (storms, cyclones) is confirmed [2, 3], it could lead to an increase of the export of dissolved and suspended material derived from soils. Volcanic provinces under wet tropical climate present optimal conditions for the weathering [4], including high temperature and high runoff, and account for 30% of the total soil organic carbon [5] and could be disrupted by climatic changes. Guadeloupe is selected for its geographical and geologycal settings and high rates of chemical weathering and mechanical denudation [4, 6, 7]. High-temporal resolution sampling of three small watersheds was performed since 2007 and a biannual sampling, during low water level and floods, was made in rivers of the Basse-Terre island. We quantified concentrations and fluxes of dissolved and particulate organic carbon (DOC, POC) as well as dissolved inorganic carbon (DIC). Organic carbon was also characterised by its isotopic composition (δ13CDOC) and its Specific UV Absorbance at the wavelengh 254 nm (SUVA254). DOC values range from 0.4 to 5.0 mg/L and increase with increasing rivers discharge. δ13CDOC varies between -32.8 ‰ and -26.2 ‰ for whole rivers which emphasized different carbon input according to the type of hydrologic events. Similarly, SUVA254 values vary between 2 and 6. Indeed, the high SUVA254 values are observed during floods and indicate that the aromaticity of organic matter increases during flood events. The less negative δ13C values and the high aromaticity for flood event samples are interpreted as the result of an increase of SOM inputs during these events. [1] Gregory et al. (1999) Inter. Geosph.-Biosph. Prog. Book, 4. [2] Emmanuel (2005) Nature, 436. [3] Webster et al. (2005) Science, 309. [4] Dessert et al. (2003) Chem. Geol., 202. [5] Batjes (1996) Europ. Journ. of Soil Science, 47. [6] Louvat (1997) PhD. [7] Rad et al. (2006) Journ. of Geoch. Explo., 88.
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Submitted on : Monday, August 31, 2009 - 11:31:35 AM
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  • HAL Id : insu-00411942, version 1


E. Lloret, C. Dessert, Patrick Albéric, Jérôme Gaillardet, M.F. Benedetti. Impact of climatic changes on organic carbon dynamic in wet tropical watersheds of Guadeloupe (FWI).. 19th Annual VM Goldschmidt Conference, Jun 2009, Davos, Switzerland. pp.A780. ⟨insu-00411942⟩



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