The state of Lake Simcoe (Ontario, Canada): The effects of multiple stressors on phosphorus and oxygen dynamics

Authors

R. L. North, Trent University
D. Barton, University of Waterloo
A. S. Crowe, Environment and Climate Change Canada
P. J. Dillon, Trent University
R. M.L. Dolson, Ontario Ministry of Natural Resources
D. O. Evans, Trent University
B. K. Ginn, Lake Simcoe Region Conservation Authority
L. Håkanson, Uppsala Universitet
J. Hawryshyn, Queen’s University
H. Jarjanazi, Ontario Ministry of the Environment
J. W. King, University of Rhode Island
J. K.L. La Rose, Ontario Ministry of Natural Resources
L. León, Environment and Climate Change Canada
C. F.M. Lewis, Geological Survey of Canada
G. E. Liddle, Ontario Ministry of Natural Resources
Z. H. Lin, Trent University
F. J. Longstaffe, Western University
R. A. Macdonald, Western University
L. Molot, York University
T. Ozersky, Trent University
M. E. Palmer, Ontario Ministry of the Environment
R. Quinlan, York University
M. D. Rennie, Trent University
M. M. Robillard, Ontario Ministry of Natural Resources
D. Rodé, York University
K. M. Rühland, Uppsala Universitet
A. Schwalb, University of Waterloo
J. P. Smol, Queen’s University
E. Stainsby, Ontario Ministry of the Environment
J. J. Trumpickas, Ontario Ministry of Natural Resources
J. G. Winter, Ontario Ministry of the Environment
J. D. Young, Ontario Ministry of the Environment

Document Type

Article

Date of Original Version

3-25-2013

Abstract

Lake Simcoe, the largest lake in southern Ontario outside of the Laurentian Great Lakes, is affected by numerous stressors including eutrophication resulting from total phosphorus (TP) loading, climate change, and invasions of exotic species. We synthesized the long-term responses of Lake Simcoe to these stressors by assessing trends in water quality and biological composition over multiple trophic levels. Evidence for climate change included increasing thermal stabilityof the lake and changes in subfossil diatom communities over time. Although the deep water dissolved oxygen (O2) minimumhas increased significantly since TP load reductions, it is still below estimated historical values and the Lake Simcoe Protection Plan end-of-summer target level of 7 mg O2 L-1. Low deep water O2 concentrations corresponded with a decline in coldwater fish abundance. Since 1980, some nutrient concentrations have decreased (spring TP) while others have increased (silica), but many show no obvious changes (ice-free TP, nitrate, ammonium). Increases in water clarity, combined with declines in chlorophyll a and phytoplankton biovolumes in Cook's Bay, were temporally consistent with declines in TPloading and the lake-wide establishment of dreissenid mussels as a major component of the Lake Simcoe ecosystem. Using an investigative tool, we identified 2 periods when abrupt shifts potentially occurred in multiple parameters: 1986 and 1995-1997. Additional ecosystem level changes such as declines in zooplankton, declines in offshore benthic invertebrate abundance, and increased nearshore invertebrate abundance likely reflect the effects of invasive species. The interaction of these multiple stressors have significantly altered the Lake Simcoe ecosystem. © Her Majesty the Queen in Right of Canada, as represented by Environment Canada 2013.

Publication Title, e.g., Journal

Inland Waters

Volume

3

Issue

1

Citation/Publisher Attribution

North, R. L., D. Barton, A. S. Crowe, P. J. Dillon, R. M. Dolson, D. O. Evans, B. K. Ginn, L. Håkanson, J. Hawryshyn, H. Jarjanazi, J. W. King, J. K. La Rose, L. León, C. F. Lewis, G. E. Liddle, Z. H. Lin, F. J. Longstaffe, R. A. Macdonald, L. Molot, T. Ozersky, M. E. Palmer, R. Quinlan, M. D. Rennie, M. M. Robillard, D. Rodé, K. M. Rühland, A. Schwalb, J. P. Smol, E. Stainsby, J. J. Trumpickas, J. G. Winter, and J. D. Young. "The state of Lake Simcoe (Ontario, Canada): The effects of multiple stressors on phosphorus and oxygen dynamics." Inland Waters 3, 1 (2013). doi: 10.5268/IW-3.1.529.