Seasonal Inundation Pulses and Biogeochemical Cycling in the Pantanal Wetland

Seasonal Inundation Pulses and Biogeochemical Cycling in the Pantanal Wetland

Sprawling across western Brazil and extending into adjacent sectors of Bolivia and Paraguay, the Pantanal represents the largest tropical wetland on the planet. This colossal tectonic depression, situated within the Upper Paraguay River Basin, undergoes a dramatic annual flood pulse that reshapes the entire regional landscape. During the wet season, torrential tropical rains swell headwater tributaries, sending immense volumes of runoff into the low-gradient basin. Because the regional gradient declines by merely a few centimetres per kilometre, drainage proceeds at a remarkably sluggish pace. Consequently, rising waters overtop riverbanks and submerge up to eighty percent of the alluvial plain, transforming disparate savannas and dry scrublands into an expansive inland sea.

This hydrological cycle triggers a complex biogeochemical process known locally as the decoada. As floodwaters submerge terrestrial pastures, decomposing plant biomass rapidly depletes dissolved oxygen from the water column.