Igapó is the Amazon forest type flooded by acidic, nutrient-poor blackwater rivers.
Blackwater rivers often drain soils rich in organic matter and carry tannins from decomposing vegetation, giving the water a dark tea-like appearance. Their low sediment and nutrient content helps create conditions different from those in whitewater floodplains.
Igapó forests may remain flooded for months during the annual river cycle. Trees and other plants have specialized adaptations, including tolerance of waterlogged soils and reduced oxygen around their roots.
Igapó is often confused with várzea. Várzea is associated with sediment-laden whitewater and generally more fertile floodplain soils, while igapó is linked to blackwater systems. Both habitats are biologically important but are not interchangeable terms.