Organic Matter Is a Mixture of Terrestrial, Autochthonous, and Wastewater Effluent in an Urban River

Abstract

Terrestrially derived organic matter (OM) is known to dominate the OM pool in reference watersheds. Urban watersheds are known to receive large OM loads compared to reference watersheds, but the proportion of terrestrial, autochthonous, and anthropogenic (e.g., wastewater effluent) sources of OM in urban watersheds remains unknown. Organic matter was identified as a pollutant of concern in the Jordan River, an urban river in the Salt Lake Basin, U.S.A. Our objective was to identify autochthonous, terrestrial, and anthropogenic sources of three size-classes of OM to the Jordan River to inform OM reduction strategies within the watershed. Samples of coarse particulate OM (CPOM), fine particulate OM (FPOM), and dissolved OM (DOM) were analyzed for stable isotopes of carbon, nitrogen, and hydrogen. Stable isotope values of OM were used for Bayesian and graphical gradient-based mixing models to identify autochthonous, terrestrial, and anthropogenic sources. Fluorescent properties of DOM were also used to characterize the sources and composition of DOM. CPOM was primarily terrestrially derived with increased autochthonous inputs from macrophytes in warm months. FPOM was a mixture of terrestrial, autochthonous, and wastewater effluent throughout the year. DOM was primarily from wastewater effluent as well as DOM with isotope signatures unique to DOM from Utah Lake. Characterization of OM in urban rivers will help inform conceptual models of OM dynamics and load management in urban ecosystems.

Ditching Nutrients: Roadside Drainage Networks are Hotspots for Microbial Nitrogen Removal

“…Agriculture depletes soil OM (McLauchlan, 2006) and increases both allochthonous OM inputs and DOM lability in aquatic ecosystems (Shang et al., 2018; Stanley et al., 2012). Urbanization also increases DOM lability in surface waters due to increased wastewater inputs and autochthonous production (Kelso & Baker, 2020; Z. Wu et al., 2019; Hosen et al., 2014). Both urbanization and agricultural intensification increase NO 3 − loads in runoff from fertilizer application, human and animal waste, and atmospheric deposition (Jordan & Weller, 1996).…”

Hydromorphologic Control of Streambed Fine Particle Standing Stocks Influences In-stream Aerobic Respiration

“…This idea is supported by the low C:N ratios measured at the Cànoves stream (from 12:1 to 15:1), which are substantially lower than those reported for total organic matter in rivers worldwide (from 30:1 to 60:1) (Bauer et al, 2013). In urban streams, FPOM is usually a mixture of terrestrial, autochthonous and wastewater effluent sources, the latter source contributing >50% when hydrological dilution is low (Kelso and Baker, 2020). Therefore, and given that the study reaches were downstream of a WWTP effluent, we propose that this was an important source of FPOM in the Cànoves stream.…”

“…The organic fraction of the FPM (i.e., fine particulate organic matter, FPOM) can consist of fecal particles from shredder invertebrates as well as fragments of organic particles generated both in streams and adjacent soils (Bundschuh and McKie, 2015). Stream FPOM can also derive from anthrogenic point sources such as wastewater treatment plant (WWTP) effluents which usually act as important sources of particles, dissolved organic carbon and nutrients (Marti et al, 2004;Merbt et al, 2014;Bernal et al, 2020;Kelso and Baker, 2020). Although FPOM can be highly processed organic matter; and therefore, expected to be a more recalcitrant OM source than the dissolved organic fraction, FPOM can act both as a colonizing surface for microorganisms and as a carbon source for microbial activity within streams (Hope et al, 1994;Brugger et al, 2001;Gottselig et al, 2014) and eventually can be more labile than dissolved organic matter (Stutter et al, 2007).…”

Stormwater Runoff and Tidal Flooding Transform Dissolved Organic Matter Composition and Increase Bioavailability in Urban Coastal Ecosystems

“…Additionally, we found that elevated indicators of autochthonous production increased the proportion of bioavailable DOM and were related to sources of anthropogenic waste signified SMITH ET AL. by tryptophan-like fluorescence (Kelso & Baker, 2020;Osburn et al, 2012; Figure 6). Interestingly, elevated heterotrophic BA and activities during the wet season, when the water table is high, led to shifts in microbial utilization of C from allochthonous sources to autochthonous sources.…”

“…In coastal drainages, DOM originates from a range of allochthonous and autochthonous sources including terrestrial plants and soil, bacterial or algal production contributions, and exudates from marine phytoplankton (Asmala et al., 2016; Romera‐Castillo et al., 2010; Sobczak et al., 2002). The role of DOM in biogeochemical cycling is a function of its composition (i.e., quality) and is driven by changes in land use (Kaushal & Belt, 2012; Kelso & Baker, 2020; Kominoski & Rosemond, 2012; Wilson & Xenopoulos, 2009) and hydrologic conditions, such as stormwater runoff and tidal mixing (Duan et al., 2014; Gardner, et al., 2005; Hosen et al., 2014). Despite the abundance of DOM in aquatic ecosystems, often only a small fraction is bioavailable (i.e., easily degradable; Parr et al., 2015).…”