Increased variability and sudden ecosystem state change in LakeWinnipeg, Canada, caused by 20thcentury agriculture

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dc.contributor.authorBunting, L.
dc.contributor.authorLeavitt, P.R.
dc.contributor.authorSimpson, G.L.
dc.contributor.authorWissel, B.
dc.contributor.authorLaird, K.R.
dc.contributor.authorCumming, B.F.
dc.contributor.authorSt. Amand, A.
dc.contributor.authorEngstrom, D.R.
dc.date.accessioned2023-06-30T14:48:43Z
dc.date.available2023-06-30T14:48:43Z
dc.date.issued2016-07-01
dc.description© 2016 The Authors Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.en_US
dc.description.abstractEutrophication can initiate sudden ecosystem state change either by slowly pushing lakes toward a catastrophic tipping point beyond which self-reinforcing mechanisms establish an alternate stable state, or through rapid but persistent changes in external forcing mechanisms. In principle, these processes can be distinguished by determining whether historical changes in focal parameters (phytoplankton) exhibit transient (rising then declining) or continuously-elevated variability characteristic of alternate stable states or a “paradox of enrichment,” respectively. We tested this hypothesis in the south basin of Lake Winnipeg, Canada, a site with intense blooms of N2-fixing cyanobacteria since 1990, but for which little is known of earlier limnological conditions, causes of eutrophication, or whether modern conditions represent a alternate stable state. Paleolimnological analysis revealed that the basin was naturally mesotrophic (∼15–20 μg P L−1) with diazotrophic cyanobacteria, productive diatoms, and phosphorus-rich sediments. Eutrophication accelerated during ca.1900–ca.1990, when sedimentary nitrogen, phosphorus and carbon contents increased 10–50%, δ15N enriched 3–4‰, and concentrations of many fossil pigments increased 300–500%. Nearly 75% of 20th century variability was explained by concomitant increases in production of livestock and crops, but not by climate. After ca.1990, the basin exhibited a rapid threefold increase in akinetes from Aphanizomenon and Anabaena spp. and 50% declines in pigments from chlorophytes and cyanobacteria because of sudden socio-economic reorganization of agriculture. Phytoplankton variability quantified using Gaussian generalized additive models increased continuously since the onset of agriculture for bloom-forming taxa, did not decline after state change, and suggested that recovery should not be affected by stable-state hysteresis.en_US
dc.description.authorstatusFacultyen_US
dc.description.peerreviewyesen_US
dc.description.sponsorshipManitoba Conservation and Water Stewardship Natural Science and Engineering Research Council of Canada (NSERC) Canada Research Chair program Canada Foundation for Innovation Fulbright Canada Province of Saskatchewan University of Reginaen_US
dc.identifier.citationBunting, L., P.R. Leavitt, G.L. Simpson, B. Wissel, K.R. Laird, B.F. Cumming, A. St. Amand, and D.R. Engstrom. 2016. Increased variability and sudden ecosystem state change in Lake Winnipeg, Canada, caused by 20th century agriculture. Limnol. Oceanogr. 61: 2090–2107. doi.org/10.1002/lno.10355en_US
dc.identifier.doihttps://doi.org/10.1002/lno.10355
dc.identifier.urihttps://hdl.handle.net/10294/15988
dc.language.isoenen_US
dc.publisherWileyen_US
dc.rightsAttribution-NonCommercial-NoDerivs 4.0 International*
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/*
dc.titleIncreased variability and sudden ecosystem state change in LakeWinnipeg, Canada, caused by 20thcentury agricultureen_US
dc.typeArticleen_US
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