Nutrient enrichment leading to eutrophication of lakes is frequently attributed to increasing anthropogenic loading to the watershed. We use a phosphorus mass balance model to demonstrate that a discharge increase in a major tributary contributed more than increased anthropogenic loading to a recent sudden doubling of total phosphorus (TP) and a shift to a cyanobacteria-dominated plankton population in Lake Winnipeg. Runoff from the Red River watershed rose abruptly during the mid-1990s. The decadal mean discharge has since been more than 50% higher than for any previous decade in the century-long record. Widespread spring flooding has become common. TP concentration roughly doubles during floods, magnifying the effect of higher runoff on downstream phosphorus loading. Concentrations of both dissolved and particulate phases are raised by flooding. Over 90% of dissolved phosphorus downstream of flooded farm land in one tributary was in the form of highly bio-available orthophosphate. From 1994 to 1999, TP in the lake rose from less than 30 to more than 50 mg m− 3. It has since remained over 50% higher than before the mid-1990s. We use the phosphorus model to demonstrate that the change in Red River discharge alone would have caused a sustained 32% increase compared to when phosphorus was first routinely monitored in the 1970s, while direct increases in the rate of anthropogenic loading alone would have caused only a 14% increase. It required both increased loading to the land and higher runoff to produce the observed increase in TP in the lake.

Metadata

Field Value
Title Hydrological forcing of a recent trophic surge in Lake Winnipeg
Publication general type journal article
Project Name The Manitoba Great Lakes Program
Keywords Cyanobacteria, Eutrophication, Freshwaters, Manitoba, Nutrient inputs, Phosphorus
Keyword Vocabulary Polar Data Catalogue
Keyword Vocabulary URL https://www.polardata.ca/pdcinput/public/keywordlibrary
Theme Freshwater
Version 1.0
Publisher Journal of Great Lakes Research
Date Published 2012
DOI 10.1016/j.jglr.2011.12.012
Language English
Preferred citation McCullough, Gregory K., Stephen J. Page, Raymond H. Hesslein, Michael P. Stainton, Hedy J. Kling, Alex G. Salki, and David G. Barber. 2012. “Hydrological Forcing of a Recent Trophic Surge in Lake Winnipeg.” Journal of Great Lakes Research 38 (January): 95–105. https://doi.org/10.1016/j.jglr.2011.12.012
Field Value
Authors
Authors 1
Author Name
McCullough, Greg
Type of Name
Personal
Email
greg.mccullough@gmail.com
Affiliation
Centre for Earth Observation Science - University of Manitoba
ORCID ID
Authors 2
Author Name
Page, Stephan J.
Type of Name
Personal
Email
Stephen.Page@dfo-mpo.gc.ca
Affiliation
Fisheries and Oceans Canada
ORCID ID
Authors 3
Author Name
Hesslein, Raymond H.
Type of Name
Personal
Email
hesslein@mymts.net
Affiliation
Freshwater Institute - Fisheries and Oceans Canada
ORCID ID
Authors 4
Author Name
Stainton, Michael P.
Type of Name
Personal
Email
Affiliation
Freshwater Institute - Fisheries and Oceans Canada
ORCID ID
Authors 5
Author Name
Kling, Hedy J.
Type of Name
Personal
Email
hedy.kling8@gmail.com
Affiliation
Algal Taxonomy and Ecology Inc.
ORCID ID
Authors 6
Author Name
Salki, Alex G.
Type of Name
Personal
Email
Affiliation
Freshwater Institute - Fisheries and Oceans Canada
ORCID ID
Authors 7
Author Name
Barber, David G.
Type of Name
Personal
Email
david.barber@umanitoba.ca
Affiliation
Centre for Earth Observation Science - University of Manitoba
ORCID ID
Field Value
License Name
Licence Type
Licence Schema Name SPDX
Licence URL https://spdx.org/licenses
Field Value
Funded by
Website
Funder Name
Funder Identifier Code
Funder Identifier Type
Funder Identifier Scheme
Grant Number