Rising nitrate concentrations in streams draining into Lake Ontario

Ann Arbor, Mich. — Nitrate concentrations in Lake Ontario and the other Great Lakes have increased in recent decades, which can have negative consequences for lake ecology.

In this study, seasonal nitrate concentrations were examined in 15 major streams draining into Lake Ontario between the 1970s and 2000s to determine whether stream nitrate had also increased. The researchers found that nitrate concentrations increased at the majority (13/15) of the tributaries, and increases were particularly large in some seasons (up to 6-fold). Stream nitrate concentrations were equally high at agriculturally-dominated and urban-dominated streams, but nitrate only increased significantly at the agricultural streams.

While the cause(s) of these increases remain uncertain, the research suggests that shifts in agricultural land use in southern Ontario over the past four decades may be responsible. In particular, increases in corn-soybean production and associated tile drainage at the expense of perennial crops like hay and pasture land, is of concern. Further research into the causes of long-term changes in nutrient export from Great Lakes watersheds is warranted.

Original Publication Information

Results of this study, "Increasing nitrate concentrations in streams draining into Lake Ontario Journal of Great Lakes Research," are reported by M. Catherine Eimers and Shaun A. Watmough in Volume 42, Issue 2 of the Journal of Great Lakes Research, published by Elsevier, 2016.

Contacts

For more information about the study, contact Dr. Catherine Eimers, 1600 West Bank Drive, Trent University, Peterborough, Ontario, Canada K9J 7B8; (705) 748 - 1011 Ext. 7225 ; [email protected].

For information about the Journal of Great Lakes Research, contact Stephanie Guildford, Scientific Co-Editor, Large Lakes Observatory, University Minnesota Duluth, 2205 East Fifth Street, Duluth, Minnesota, 55812-2401; [email protected]; (218) 726-8064.