Anthropogenic Influence on Greenhouse Gas fluxes in a Tropical Natural Wetland

116This study determined the fluxes of CO₂, CH₄ and N₂O emitted from a eutrophic tropical freshwater wetland (FW) called Sonso Lagoon. This FW receives pollution from several sources including agricultural run-off, domestic sewage, and a polluted river. The results indicate that the fluxes for CO₂, CH₄ and N₂O showed a large variation ranging from consumption to emissions. CO₂ fluxes ranged from −22.9 to 23 g.m^-2.d^-1 (median = 0.93), CH₄ ranged between −3.03 and 9.83 g.m^-2.d^-1 (median = 0.04), and N₂O ranged from −15.2 to 12.6 mg N₂O m^-2.d^-1 (median = 0.21). For all the three gases studied, negative fluxes were observed mainly in the zone dominated by floating aquatic macrophytes i.e. Eichornia crassipes, Salvinia sp., and Pistia stratiotes L. However, the mean values indicated that the Sonso Lagoon was a net source of GHG production. The effect of eutrophication on GHG emissions could be observed in the positive correlation found between CH₄ and CO₂ generation and COD, PO₄ ^-3 and NH₄-N. In addition, N₂O correlated positively to TKN and NO₃ ^-N. This study demonstrates that pollution and eutrophication of natural wetlands results in net emissions of greenhouse gases into the atmosphere.