Effects of experimental nitrogen fertilization on planktonic metabolism and CO2 flux in a hypereutrophic hardwater lake

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dc.contributor.authorBogard, Matthew J.
dc.contributor.authorFinlay, Kerri
dc.contributor.authorWaiser, Marley J.
dc.contributor.authorTumber, Vijay P.
dc.contributor.authorDonald, Derek B.
dc.contributor.authorWiik, Emma
dc.contributor.authorSimpson, Gavin L.
dc.contributor.authordel Giorgio, Paul A.
dc.contributor.authorLeavitt, Peter R.
dc.date.accessioned2023-06-09T20:50:51Z
dc.date.available2023-06-09T20:50:51Z
dc.date.issued2017-12-12
dc.description© 2017 Bogard et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.en_US
dc.description.abstractHardwater lakes are common in human-dominated regions of the world and often experience pollution due to agricultural and urban effluent inputs of inorganic and organic nitrogen (N). Although these lakes are landscape hotspots for CO2 exchange and food web carbon (C) cycling, the effect of N enrichment on hardwater lake food web functioning and C cycling patterns remains unclear. Specifically, it is unknown if different eutrophication scenarios (e.g., modest non point vs. extreme point sources) yield consistent effects on auto- and heterotrophic C cycling, or how biotic responses interact with the inorganic C system to shape responses of air-water CO2 exchange. To address this uncertainty, we induced large metabolic gradients in the plankton community of a hypereutrophic hardwater Canadian prairie lake by adding N as urea (the most widely applied agricultural fertilizer) at loading rates of 0, 1, 3, 8 or 18 mg N L-1 week-1 to 3240-L, in-situ mesocosms. Over three separate 21-day experiments, all treatments of N dramatically increased phytoplankton biomass and gross primary production (GPP) two- to six-fold, but the effects of N on autotrophs plateaued at ~3 mg N L-1. Conversely, heterotrophic metabolism increased linearly with N fertilization over the full treatment range. In nearly all cases, N enhanced net planktonic uptake of dissolved inorganic carbon (DIC), and increased the rate of CO2 influx, while planktonic heterotrophy and CO2 production only occurred in the highest N treatments late in each experiment, and even in these cases, enclosures continued to in-gas CO2. Chemical effects on CO2 through calcite precipitation were also observed, but similarly did not change the direction of net CO2 flux. Taken together, these results demonstrate that atmospheric exchange of CO2 in eutrophic hardwater lakes remains sensitive to increasing N loading and eutrophication, and that even modest levels of N pollution are capable of enhancing autotrophy and CO2 in-gassing in P-rich lake ecosystemen_US
dc.description.authorstatusFacultyen_US
dc.description.peerreviewyesen_US
dc.description.sponsorshipThis work was supported by the Natural Sciences and Engineering Research Council of Canada Discovery Grants, the Canada Research Chair Program, Canada Foundation for Innovation, Fulbright Canada, the Province of Saskatchewan, the University of Regina, and Nature Regina.en_US
dc.identifier.citationBogard, M.J., K. Finlay, M.J. Waiser, V.P. Tumber, D.B. Donald, E. Wiik, G.L. Simpson, P.A. del Giorgio, and P.R. Leavitt. 2017. Effects of experimental nitrogen fertilization on planktonic metabolism and CO2 flux in a hypereutrophic hardwater lake. PLoS One 12 (12): e0188652. doi.org/10.1371/journal.pone.0188652en_US
dc.identifier.doihttps://doi.org/10.1371/journal.pone.0188652
dc.identifier.urihttps://hdl.handle.net/10294/15953
dc.language.isoenen_US
dc.publisherPublic Library of Scienceen_US
dc.rightsAttribution 4.0 United States*
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/*
dc.titleEffects of experimental nitrogen fertilization on planktonic metabolism and CO2 flux in a hypereutrophic hardwater lakeen_US
dc.typeArticleen_US
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