Abstract

BETANCOURT-PORTELA, Julián Mauricio; PARRA, Juan Pablo  and  VILLAMIL, Carlos. METHANE AND NITROUS OXIDE EMISSION OF MANGROVE SEDIMENTS AT THE CIÉNAGA GRANDE DE SANTA MARTA, COLOMBIAN CARIBBEAN. Bol. Invest. Mar. Cost. [online]. 2013, vol.42, n.1, pp.131-152. ISSN 0122-9761.

In Colombia there is little information on the role of mangroves in relation to greenhouse gases (GHG), their release rates under different environmental conditions, or their role in the global carbon cycle. For these reasons, in this study we evaluated the fluxes of CH₄ and N₂O, in four sectors of the Ciénaga Grande de Santa Marta (CGSM) with different degrees of conservation of mangrove forests, to determine their role as a source or sink of GHG. The fluxes were measured by the method of the static chambers and showed variations between 34.7-1179.7 and nd-31569.2 µg.m^-2.h^-1 for N₂O and CH₄, respectively, showing that mangrove sediments of CGSM are a net source of GHG, and furthermore are of the same magnitude as levels recorded world-wide in mangroves subjected to sewage input. Statistical analyses showed differences between sectors but not between climatic periods. N₂O emissions were highest in the Agua Negras station (AN, 847.3 ± 265.7 µg.m^-2.h^-1), a locality in the process of natural regeneration with a direct influence from the Magdalena River and in Caño Dragado (CD, 438.7 ± 235.3 µg.m^-2.h^-1); while emissions were lower in the recovery sites Caño Grande (CG) and Rinconada (RIN), (104.7 ± 49.4 and 152.1 ± 36.0 µg.m^-2.h^-1, respectively). The highest CH₄ emission was recorded in recovery sectors: CG and AN (9573.4 ± 8623.8 and 4328.2 ± 7569.5 µg.m^-2.h^-1, respectively). In terms of CO₂-equivalent, N₂O emissions account for over 50% of the total, and this has been documented for agricultural systems and constitutes evidence of deterioration of CD. A correlation analysis with environmental factors showed that N₂O emissions vary inversely with salinity and positively with nitrites, suggesting production mainly via nitrification. Finally, a coarse estimation of GHG emissions per hectare indicated that, depending on the state of conservation or deterioration of the mangrove, emissions can vary from 10.2 to 27.1 tCO₂-eq.ha^-1.a^-1.

Keywords : Greenhouse gases; methane flux; nitrous oxide flux; mangroves.

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