Increases in humic and bioavailable dissolved organic matter in a forested New England headwater stream with increasing discharge
Henry F. Wilson A B E , Peter A. Raymond A , James E. Saiers A , William V. Sobczak C and Na Xu A D
+ Author Affiliations
- Author Affiliations
A School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA.
B Brandon Research Center, Agriculture and Agri-Food Canada, 2701 Grand Valley Road, Brandon, MB, R7A 5Y3, Canada.
C Biology Department, Holy Cross College, 1 College Street, Worcester, MA 01610, USA.
D Risk Management Solutions, 7575 Gateway Boulevarde, Newark, CA 94560, USA.
E Corresponding author. Email: henry.wilson@agr.gc.ca
Marine and Freshwater Research 67(9) 1279-1292 https://doi.org/10.1071/MF15286
Submitted: 30 July 2015 Accepted: 15 November 2015 Published: 11 February 2016
Abstract
Understanding the processes controlling the transfer of organic matter from terrestrial to aquatic ecosystems is of fundamental importance for the aquatic sciences. Over the course of a full year, fluorescence, absorbance and bioavailability of dissolved organic matter (DOM) were characterised in Bigelow Brook, a forested headwater stream in Massachusetts, USA. Parallel factor analysis (PARAFAC) identified a four-component model to describe observed DOM fluorescence (C1–C4). Component C2 exhibited the characteristics of a more humic-like fluorophore, with a potentially more reduced redox state and increased with discharge, whereas more fulvic-like (C1) and protein-like (C3, C4) fluorophores decreased. Under both dark and light-exposed conditions, percentage bioavailable dissolved organic carbon (%BDOC) increased with discharge (R2 = 0.37 and R2 = 0.56). C2 and specific absorptivity (SUVA) were reduced following BDOC incubations, whereas C1, C3 and C4 increased. These changes to DOM characteristics with increasing discharge were observed under both baseflow and stormflow conditions, indicating that with rising watertable, loading from a large riparian or hyporheic pool of organic matter is likely occurring. Other headwater streams, where loading is controlled by hillslope processes, are likely to exhibit a similar pattern of increasing export of more humic and bioavailable DOM during hydrologic events.
Additional keywords: hydrologic events, hydrology, secondary production, stream ecology.
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