Editing Littoral zone (section)

==In freshwater ecosystems==
[[File:Primary zones of a lake.png|thumb|upright=1.7| The three primary zones of a lake are the littoral zone, the open-water (also called the [[Photic zone|photic]] or [[Limnetic zone|limnetic]]) zone, and the deep-water (also called the [[aphotic zone|aphotic]] or [[profundal zone|profundal]]) zone.]]
[[File:Moon Lake shoreline - Riding Mountain National Park.JPG|thumb|right|Shoreline of a lake with nearly unvegetated littoral zone]]

In freshwater situations, the littoral zone is the nearshore habitat where [[photosynthetically active radiation]] penetrates to the lake bottom in sufficient quantities to support photosynthesis.<ref name=Seekell2021 /> Sometimes other definitions are used. For example, the [[Minnesota Department of Natural Resources]] defines littoral as that portion of the lake that is less than 15 [[foot (length)|feet]] in depth.<ref>{{cite web|url=http://www.dnr.state.mn.us/lakefind/surveys.html#littoral|title=Fisheries lake surveys|website = Minnesota Department of Natural Resources}}</ref> Such fixed-depth definitions often do not accurately represent the true ecological zonation, but are sometimes used because they are simple measurements to make bathymetric maps or when there are no measurements of light penetration. The littoral zone comprises an estimated 78% of Earth's total lake area.<ref name=Seekell2021 />

The littoral zone may form a narrow or broad fringing wetland, with extensive areas of aquatic plants sorted by their tolerance to different water depths. Typically, four zones are recognized, from higher to lower on the shore: wooded wetland, [[wet meadow]], [[marsh]] and [[aquatic vegetation]].<ref name = keddy2>Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. Chapter 2.</ref> The relative areas of these four types depends not only on the profile of the shoreline, but upon past water levels. The area of wet meadow is particularly dependent upon past water levels;<ref name="Keddy, P.A 2010">Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK.</ref> in general, the area of wet meadows along lakes and rivers increases with natural water level fluctuations.<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. USGS Circular 1311. 25 p.</ref><ref>Hughes, F.M.R. (ed.). 2003. The Flooded Forest: Guidance for policy makers and river managers in Europe on the restoration of floodplain forests. FLOBAR2, Department of Geography, University of Cambridge, Cambridge, UK. 96 p.</ref> Many of the animals in lakes and rivers are dependent upon the wetlands of littoral zones, since the rooted plants provide habitat and food. Hence, a large and productive littoral zone is considered an important characteristic of a healthy lake or river.<ref name="Keddy, P.A 2010"/>

Littoral zones are at particular risk for two reasons. First, human settlement is often attracted to shorelines, and settlement often disrupts breeding habitats for littoral zone species. For example, many turtles are killed on roads when they leave the water to lay their eggs in upland sites. Fish can be negatively affected by docks and retaining walls which remove breeding habitat in shallow water. Some shoreline communities even deliberately try to remove wetlands since they may interfere with activities like swimming. Overall, the presence of human settlement has a demonstrated negative impact upon adjoining wetlands.<ref>{{cite journal|last1=Houlahan |first1=J. E.|last2=Keddy|first2=P. A.|last3=Makkay|first3=K.|last4=Findlay|first4=C. S.|title=The effects of adjacent land use on wetland species richness and community composition|journal=Wetlands|date=2006|volume=26|issue=1|pages=79–96|doi=10.1672/0277-5212(2006)26[79:TEOALU]2.0.CO;2|s2cid=8050261 }}</ref> An equally serious problem is the tendency to stabilize lake or river levels with dams. Dams removed the spring flood, which carries nutrients into littoral zones and reduces the natural fluctuation of water levels upon which many wetland plants and animals depend.<ref>{{cite book|editor-last =Middleton|editor-first= B. A. |date = 2002|title = Flood Pulsing in Wetlands: Restoring the Natural Hydrological Balance|publisher= John Wiley|location = New York|bibcode= 2002fpwr.book...12M }}</ref><ref>Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497. Chapter 2.</ref> Hence, over time, dams can reduce the area of wetland from a broad littoral zone to a narrow band of vegetation. Marshes and wet meadows are at particular risk.