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Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream

1
Molecular Eco-Geochemistry (MEG) Laboratory, Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
2
Alabama Water Institute, University of Alabama, Tuscaloosa, AL 35487, USA
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State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
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Department of Chemistry & Biochemistry, University of Alabama, Tuscaloosa, AL 35487, USA
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Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Bommanna Krishnappan
Water 2021, 13(20), 2919; https://doi.org/10.3390/w13202919
Received: 8 August 2021 / Revised: 8 October 2021 / Accepted: 10 October 2021 / Published: 17 October 2021
(This article belongs to the Section Water Quality and Contamination)
Streams in the southeastern United States Coastal Plains serve as an essential source of energy and nutrients for important estuarine ecosystems, and dissolved organic matter (DOM) exported from these streams can have profound impacts on the biogeochemical and ecological functions of fluvial networks. Here, we examined hydrological and temperature controls of DOM during low-flow periods from a forested stream located within the Coastal Plain physiographic region of Alabama, USA. We analyzed DOM via combining dissolved organic carbon (DOC) analysis, fluorescence excitation–emission matrix combined with parallel factor analysis (EEM-PARAFAC), and microbial degradation experiments. Four fluorescence components were identified: terrestrial humic-like DOM, microbial humic-like DOM, tyrosine-like DOM, and tryptophan-like DOM. Humic-like DOM accounted for ~70% of total fluorescence, and biodegradation experiments showed that it was less bioreactive than protein-like DOM that accounted for ~30% of total fluorescence. This observation indicates fluorescent DOM (FDOM) was controlled primarily by soil inputs and not substantially influenced by instream production and processing, suggesting that the bulk of FDOM in these streams is transported to downstream environments with limited in situ modification. Linear regression and redundancy analysis models identified that the seasonal variations in DOM were dictated primarily by hydrology and temperature. Overall, high discharge and shallow flow paths led to the enrichment of less-degraded DOM with higher percentages of microbial humic-like and tyrosine-like compounds, whereas high temperatures favored the accumulation of high-aromaticity, high-molecular-weight, terrestrial, humic-like compounds in stream water. The flux of DOC and four fluorescence components was driven primarily by water discharge. Thus, the instantaneous exports of both refractory humic-like DOM and reactive protein-like DOM were higher in wetter seasons (winter and spring). As high temperatures and severe precipitation are projected to become more prominent in the southeastern U.S. due to climate change, our findings have important implications for future changes in the amount, source, and composition of DOM in Coastal Plain streams and the associated impacts on downstream carbon and nutrient supplies and water quality. View Full-Text
Keywords: DOM; fluorescence; Coastal Plain stream; carbon export; flow path; climate change; biodegradation; EEM-PARAFAC; redundancy analysis DOM; fluorescence; Coastal Plain stream; carbon export; flow path; climate change; biodegradation; EEM-PARAFAC; redundancy analysis
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MDPI and ACS Style

Lu, Y.; Shang, P.; Chen, S.; Du, Y.; Bonizzoni, M.; Ward, A.K. Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream. Water 2021, 13, 2919. https://doi.org/10.3390/w13202919

AMA Style

Lu Y, Shang P, Chen S, Du Y, Bonizzoni M, Ward AK. Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream. Water. 2021; 13(20):2919. https://doi.org/10.3390/w13202919

Chicago/Turabian Style

Lu, Yuehan, Peng Shang, Shuo Chen, Yingxun Du, Marco Bonizzoni, and Amelia K. Ward 2021. "Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream" Water 13, no. 20: 2919. https://doi.org/10.3390/w13202919

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