Hydrologic and biogeochemical drivers of dissolved organic carbon and nitrate uptake in a headwater stream network
- 910 Downloads
Headwater streams are foci for nutrient and energy loading from terrestrial landscapes, in situ nutrient transformations, and downstream transport. Despite the prominent role that headwater streams can have in regulating downstream water quality, the relative importance of processes that can influence nutrient uptake have not been fully compared in heterotrophic aquatic systems. To address this research need, we assessed the seasonality of dissolved organic carbon (DOC) and nitrate (NO3−) uptake, compared the relative influence of hydrologic and biogeochemical drivers on observed seasonal trends in nutrient uptake, and estimated the influence of these biological transformations on watershed scale nutrient retention and export. We determined that seasonal reductions in DOC and NO3− concentrations led to decreases in the potential for the biotic community to take up nutrients, and that seasonality of DOC and NO3− uptake was consistent with the seasonal dynamics of ecosystem metabolism. We calculated that that during the post-snowmelt period (June to August), biotic retention of both dissolved organic carbon and nitrate exceeded export fluxes from this headwater catchment, highlighting the potential for biological processes to regulate downstream water quality.
KeywordsDissolved organic Carbon Nitrogen Nutrient uptake TASCC Residence time Watershed export
Financial support for this project was provided by Duke University, the National Science Foundation (NSF) Graduate Research Fellowship Program, NSF Grant #1114392, and USDA Award #2012-67019-19360. We would like to thank Maggie Zimmer, Kendra Kaiser, Andrew Burch, and Patrick Clay for assistance with fieldwork. We thank the Tenderfoot Creek Experimental Forest for allowing us access to the site and providing logistical support.
- Bennett JP, Rathburn RE (1972) Reaeration in open-channel flow. Geological Survey Professional Paper 737, U. S. Government Printing Office, Washington, DCGoogle Scholar
- Bernhardt ES, Likens GE (2002) Dissolved organic carbon enrichment alters stream nitrogen dynamics in a forest stream. Ecology 83:1689–1700. https://doi.org/10.1890/0012-9658(2002)083[1689:DOCEAN]2.0.CO;2 CrossRefGoogle Scholar
- Bernhardt ES, Likens GE, Hall RO et al (2005) Can’t see the forest for the stream? In-stream processing and terrestrial nitrogen exports. Bioscience 55:219–230. https://doi.org/10.1641/0006-3568(2005)055[0219:ACSTFF]2.0.CO;2 CrossRefGoogle Scholar
- Cory RM, Harrold KH, Neilson BT, Kling GW (2015) Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substrate-limitation of photo-degradation. Biogeosci Discuss 12:9793–9838. https://doi.org/10.5194/bgd-12-9793-2015 CrossRefGoogle Scholar
- Harvey J (2016) Hydrologic exchange flows and their ecological consequences in river corridors. In: Stream ecosystems in a changing environment, pp 1–83. https://doi.org/10.1016/B978-0-12-405890-3.00001-4
- Kilpatrick FA, Cobb ED (1985) Measurement of discharge using tracers. Report of the U.S. Geological Survey, Techniques of Water Resources Investigations Book 3, Chap A16, pp 6–15Google Scholar
- Melching CS, Flores HE, Flores HE (1999) Reaeration equations derived from U.S. Geological Survey database. J Environ Eng. https://doi.org/10.1061/(asce)0733-9372(1999)125:5(407) Google Scholar
- Mulholland PJ (2004) The importance of in-stream uptake for regulating stream concentrations and outputs of N and P from a forested watershed: evidence from long-term chemistry records for Walker Branch Watershed. Biogeochemistry 70:403–426. https://doi.org/10.1007/s10533-004-0364-y CrossRefGoogle Scholar
- Redfield AC (1958) The biological control of chemical factors in the environment. Am Sci 46:205–221Google Scholar
- Simon KS, Townsend CR, Biggs BJF, Bowden WB (2005) Temporal variation of N and P uptake in 2 New Zealand streams. J North Am Benthol Soc 24:1–18. https://doi.org/10.1899/0887-3593(2005)024<0001:TVONAP>2.0.CO;2
- Sterner RW, Elser JJ (2002) Ecological stoichiometry: the biology of elements from molecules to the biosphere. Princeton University Press, PrincetonGoogle Scholar
- Vitousek PM, Aber JD, Howarth RW et al (1997) Human alteration of the global nitrogen cycle: sources and consequences. Ecol Appl 7:737–750Google Scholar
- Wollheim WM, Vörösmarty CJ, Peterson BJ, Seitzinger SP, Hopkinson CS (2006) Relationship between river size and nutrient removal. Geophys Res Lett 33(6). https://doi.org/10.1029/2006GL025845.