Editing Lake Ontario (section)

==Ecology==
[[File:USGS image cropped.jpg|thumb|Profile of coastal wetlands for Lake Ontario]]
The Great Lakes watershed is a region of high biodiversity, and Lake Ontario is important for its diversity of birds, fish, reptiles, amphibians, and plants. Many of these special species are associated with shorelines, particularly sand dunes, lagoons, and wetlands. The importance of wetlands to the lake has been appreciated, and many of the larger wetlands have protected status. These wetlands are changing, partly because the natural water level fluctuations have been reduced. Many wetland plants are dependent upon low water levels to reproduce.<ref>Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Chapters 1 and 2.</ref> When water levels are stabilized, the area and diversity of the marsh is reduced. This is particularly true of meadow marsh (also known as [[wet meadow]] wetlands); for example, in Eel Bay near Alexandria Bay, regulation of lake levels has resulted in large losses of wet meadow.<ref>Wilcox, D.A, Thompson, T.A., Booth, R.K., and Nicholas, J.R. 2007. Lake-level variability and water availability in the Great Lakes. U.S. Geological Survey Circular 1311.Box 4</ref> Often this is accompanied by the invasion of [[Typha|cattails]], which displace many of the native plant species and reduce plant diversity. [[Eutrophication]] may accelerate this process by providing nitrogen and phosphorus for the more rapid growth of competitively dominant plants.<ref>Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p.</ref> Similar effects are occurring on the north shore, in wetlands such as Presqu'ile, which have interdunal wetlands called [[Salt pannes and pools|pannes]], with high plant diversity and many unusual plant species.<ref>Moore, D. R. J. and Keddy, P. A. (1989). The relationship between species richness and standing crop in wetlands: the importance of scale. Vegetation, 79, 99–106.</ref>
[[File:Lake Ontario food web.pdf|thumb|Lake Ontario's food web]]
Most of the forests around the lake are [[temperate deciduous forest|deciduous forests]] dominated by trees including maple, oak, beech, ash and basswood. These are classified as part of the [[Mixedwood Plains Ecozone (Canada)|Mixedwood Plains Ecozone]] by Environment Canada, or as the [[Eastern Great Lakes and Hudson Lowlands (ecoregion)|Eastern Great Lakes and Hudson Lowlands]] by the [[United States Environmental Protection Agency]], or as the Great Lakes Ecoregion by The Nature Conservancy.<ref>{{cite web |url=http://science.natureconservancy.ca/initiatives/blueprints/greatlakes_w.php |url-status=dead |archive-url=https://web.archive.org/web/20110611015119/http://science.natureconservancy.ca/initiatives/blueprints/greatlakes_w.php |archive-date=June 11, 2011 |title=Great Lakes |website=Nature Conservancy Canada}}</ref> Deforestation in the vicinity of the lake has had many negative impacts,<ref>[[Michael Williams (geographer)|Williams, M.]] 1989. ''Americans and Their Forests: A Historical Geography''. Cambridge: Cambridge University Press.</ref> including loss of forest birds, extinction of native salmon, and increased amounts of sediment flowing into the lake. In some areas, more than 90 percent of the [[forest cover]] has been removed and replaced by agriculture. Certain tree species, such as hemlock, have also been particularly depleted by past logging activity.<ref>Keddy, C.J. 1993. Forest History of Eastern Ontario. A report prepared for the Eastern Ontario Forest Group.</ref> Guidelines for restoration stress the importance of maintaining and restoring forest cover, particularly along streams and wetlands.<ref>Environment Canada. 2004. How Much Habitat is Enough? A Framework for Guiding Habitat Rehabilitation in Great Lakes Areas of Concern. 2nd ed. 81 p.</ref><ref>Keddy, P.A. and C. G. Drummond. 1996. Ecological properties for the evaluation, management, and restoration of temperate deciduous forest ecosystems. Ecological Applications 6: 748–762.</ref>

By the 1960s and 1970s, the increased pollution caused frequent [[algal bloom]]s to occur in the summer.<ref name="Christie, W. J. 1974"/> These blooms killed large numbers of fish, and left decomposing piles of filamentous algae and dead fish along the shores.<ref>Vallentyne, J. R. (1974). The Algal Bowl: Lakes and Man, Miscellaneous Special Publication No. 22. Ottawa, ON: Department of the Environment, Fisheries and Marine Service.</ref>

=== Water pollution ===
Lake Ontario is the most downstream lake of the Great Lakes, so the pollution from all the other lakes flows into it. Lake Ontario was ranked as the most environmentally stressed amongst the five Great Lakes in a 2015 ecological study. Some of the stresses on the lake include excess application of fertilizers in agriculture running into the lake, spillover from obsolete municipal [[sewage systems]], toxic chemicals from industries along the rivers that drain into the lake, and metropolitan drainage from big cities like Toronto, Rochester, and Hamilton.<ref>{{Cite journal |last1=Estepp |first1=Lisa R. |last2=Reavie |first2=Euan D. |date=2015-09-01 |title=The ecological history of Lake Ontario according to phytoplankton |url=https://www.sciencedirect.com/science/article/pii/S0380133015001331 |journal=Journal of Great Lakes Research |language=en |volume=41 |issue=3 |pages=669–687 |doi=10.1016/j.jglr.2015.06.005 |bibcode=2015JGLR...41..669E |issn=0380-1330|hdl=11299/186099 |hdl-access=free }}</ref>

[[Randle Reef]], the westernmost part of Lake Ontario, has been identified as one of the most contaminated areas on Lake Ontario alongside other [[Great Lakes Areas of Concern#List of areas of concern|areas of concern on Great Lakes]]. However, a $150-million cleanup project had begun in 2016 and is expected to be completed by 2025.<ref>{{Cite news |last=Rosas |first=Aura |date=7 September 2023 |title=Final stage of cleaning up contaminated Randle Reef gets underway in Hamilton Harbour |url=https://www.cbc.ca/news/canada/hamilton/randle-reef-cleaning-step-three-1.6958295 |access-date=27 December 2023}}</ref>