TABLE 1.

Functions by which NFWs affect material and energy fluxes to downstream waters.

Function	Definition	Wetland examples
	Net increase in a material or energy flux (exports > imports)	Phytoplankton production from floodplain (Schemel et al. 2004; Lehman et al. 2008)
	Net decrease in a material or energy flux (exports < imports)	Sediment deposition, denitrification (Johnson 1991)
	Avoidance of a nearby sink function, thereby preventing a net decrease in material or energy flux (exports = imports)	Riparian wetlands as aquatic refuges in dryland rivers (Leigh et al. 2010)
	Temporary storage and subsequent release of materials or energy without affecting cumulative flux (exports = imports); delivery is delayed and can be prolonged	Flood attenuation (Bullock and Acreman 2003)
	Conversion of a material or energy into a different form; the amount of the base material or energy is unchanged (base exports = base imports), but its composition (e.g., mass of the different forms) can vary	Mercury methylation (Galloway and Branfireun 2004; Selvendiran et al. 2008)

Source: Table reproduced from USEPA (2015).

Note: This review focused on source, sink, lag, and transformation functions; see Schofield et al. (2018) for refuge functions.