Nutrient footprints on the Toronto-Mississauga waterfront of Lake Ontario
Open accessAbstract
The extent of nutrient enrichment over the urbanized shoreline of western Lake Ontario bordering the Cities of Toronto and Mississauga was investigated in 2018. Concentrations of total phosphorus were higher and more wide-ranging compared with nearshore reference areas in eastern Lake Ontario. Area-weighted chlorophyll a was higher over the shoreline from the mouth of the Credit River to Humber Bay west of Toronto Harbour compared with that to the east from the Toronto Beaches to the Rouge River, a pattern also seen broadly in concentrations of phosphorus fractions and nitrates. Concentrations of phosphate measured by mass spectrometry, and using an internal standard to minimize sampling losses, were higher in Toronto Inner Harbour, near wastewater outfalls, river mouths, and to varying extent over the mixing areas of these discharges. Chlorophyll a suggested broadly oligotrophic to oligo-mesotrophic conditions despite areas with nutrient fractions suggestive of more productive conditions. Toronto Inner Harbour was mesotrophic, with wide-ranging levels of phosphorus fractions strongly influenced by the variable loading from the Don River into the harbour. Phosphorus fractions in the harbour quays which also receive CSOs discharges were elevated at times. Blooms or scums of planktonic algae were not observed. Elevated concentrations of phosphate were found at shallow depths suitable for growth of the green algae Cladophora. As these urban areas continue to grow, the potential for additional nutrient loading to exacerbate growth of algae should be watched given the present conditions that indicate variable but pervasive nutrient enrichment.
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There is a wastewater treatment plant upstream that empties into Humber Bay.
“There is also a wastewater treatment plant upstream that empties into Humber Bay.39,40”
From Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes (2024) · cites this paper as [40]
The “Phosphate and nitrate gradients near WWTP outfalls” section reports that effluent from the Humber WWTP affects Humber Bay, supporting the claim that a wastewater treatment plant discharges there. The paper does not establish that the plant is upstream of the location meant by the citing sentence; the “Study area” section distinguishes plants discharging directly to the lake from a plant upstream on the Don River. (LLM, conf=0.84)
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Cited by
Sorted by citations
Milne, M. H., Helm, P. A., Munno, K., Bhavsar, S. P., & Rochman, C. M. (2024) · Environmental Health Perspectives · doi:10.1289/ehp13540 · Cited by 15 · see citing works
- Authors
- Howell, E. T., & Benoit, N.
- Affiliations
- Ministry of the Environment, Conservation and Parks (CA)
- Corresponding author
- Howell, E.T.
- Venue
- Journal of Great Lakes Research
- Publisher
- Elsevier BV
- Published
- 2021-04
- Volume
- 47
- Issue
- 2
- Pages
- 343-365
- ISSN
- 0380-1330 (ISSN-L)
- OpenAlex
- W3110827297
- Cited by
- 10
- References
- 54
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 1 · 2023: 4 · 2021: 1
- FWCI
- 0.46
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Journal of Great Lakes Research (publishedVersion, cc-by-nc-nd)
- Topics
- Physical Sciences › Environmental Science › Environmental Chemistry › Aquatic Ecosystems and Phytoplankton Dynamics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
- Physical Sciences › Environmental Science › Environmental Chemistry › Soil and Water Nutrient Dynamics
- Keywords
- nutrient enrichment, Lake Ontario, phosphorus fractions, phosphate, chlorophyll a, nitrate, Toronto Harbour, Mississauga, Don River, combined sewer overflows, sewage outfalls, Cladophora, algal blooms, eutrophication
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