Organic matter cycling in a restored wetland receiving complex effluent

Wetlands are used to treat anthropogenic effluents due to their capacity for intense biogeochemical processing of nutrients and other pollutants, yet their role in processing effluent dissolved organic matter (DOM) is unclear. Here, I quantified the cycling of DOM in Frank Lake, an economically-important wetland restored using multiple effluent sources. Optical analyses and microbial incubations showed DOM changed from protein-like and bioavailable at the effluent inflow site to more aromatic and less bioavailable at the outflow, due to the processing and replacement of effluent DOM with that from marsh plants and wetland soils. My mass balance showed Frank Lake was a net long-term source of DOM, but shifted from a source to sink among wet and drought periods that respectively shortened or lengthened the water residence and DOM processing times. Overall, Frank Lake appears to effectively process effluent DOM, despite being a longer-term source of DOM to downstream environments.