Bioavailability and compositional changes of dissolved organic matter in urban headwaters
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Aquatic Sciences
RESEARCH ARTICLE
Bioavailability and compositional changes of dissolved organic matter in urban headwaters Megan L. Fork1,3 · Christopher L. Osburn2,4 · James B. Heffernan1 Received: 15 November 2019 / Accepted: 1 July 2020 © Springer Nature Switzerland AG 2020
Abstract In urban stream networks, the headwaters are comprised of engineered headwaters where particulate organic matter collects during and between storms. During storms, dissolved organic matter leached from these pools is transported to the stream as stormflow connects these ephemeral channels to the network. Throughout the urban network, microbial processing consumes, produces, and transforms DOM, changing its chemical composition and concentration. In this study, we characterized how microbial processing changes the composition and inferred lability of DOM from stormflow samples and leachates of potential DOM sources by pairing optical measurements of DOM composition with measurements of DOC concentration during incubation with a common bacterial community. We found that over 6 days (the approximate residence time of water stored in urban headwater infrastructure) microbial processing significantly altered DOM composition, increasing the chemodiversity of DOM in leachates but not stormflow samples. Particularly in leachates, this initial change in composition was accompanied by little change in DOC concentration. After 60 days of microbial processing, both samples of stormflow and leachates lost more than half their initial DOC concentration on average, and became more similar in composition with indices indicating humic, aromatic DOM generally considered to be recalcitrant. This work provides new evidence that leached organic matter undergoes transient increases in chemodiversity through bacterial action on the DOM pool before further processing leaves behind more homogenous and recalcitrant DOM. Keywords DOM · Biodegradation · Lability · Urban stream · CDOM · Optical properties
Introduction Dissolved organic matter (DOM) plays a central role in the ecology of aquatic environments (Prairie 2008), in part because of its role as a basal energy source. The composition Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00027-020-00739-7) contains supplementary material, which is available to authorized users. * Megan L. Fork [email protected] 1
Nicholas School of the Environment, Duke University, Durham, NC, USA
2
Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA
3
Present Address: Cary Institute of Ecosystem Studies, Millbrook, NY, USA
4
Center for Geospatial Analytics, North Carolina State University, Raleigh, NC, USA
of the DOM pool (i.e., the biochemical characteristics of the diverse mixture of molecules in DOM) partially determines its lability to degradation by microbes and by photochemical reactions, which in turn affect the concentration and composition of remaining DOM (Cory and Kling 2018). Microb
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