Disconnectivity matters: the outsized role of small ephemeral wetlands in landscape-scale nutrient retention

Abstract Wetlands protect downstream waters by filtering excess nitrogen (N) generated from agricultural and urban activities. Many small ephemeral wetlands, also known as geographically isolated wetlands (GIWs), are hotspots of N retention but have received fewer legal protections due to their apparent isolation jurisdictional waters. Here, we hypothesize that the GIWs make them more efficient filters, especially when considering transient hydrologic dynamics. We use a reduced complexity model with 30 years remotely sensed monthly wetland inundation levels in 3700 across eight wetlandscapes US show how consideration dynamics can increase estimates up 130%, greater magnification for smaller wetlands. This effect is pronounced semi-arid systems such prairies North Dakota, where assumptions lead 1.8 times retention, compared humid landscapes like Carolina Pocosins only 1.4 retention. Our results highlight an outsized role retaining nutrients, this service enhanced disconnectivity which must be protected maintain integrity