Editing San Francisco Bay (section)

==Ecology==
{{Main|Ecology of the San Francisco Estuary}}

[[File:Sf Estuary Historical.gif|thumb|300px|right|San Francisco Bay {{circa}} 1770–1820]]
[[File:South San Francisco Bay salt ponds and wildlife refuges.jpg|thumb|300px|South Bay salt ponds and wildlife refuges, aerial view from the southeast]]

Despite its urban and industrial character, San Francisco Bay and the [[Sacramento–San Joaquin River Delta]] remain perhaps California's most important [[habitat (ecology)|ecological habitats]]. California's [[Dungeness crab]], [[California halibut]], and [[Oncorhynchus|Pacific salmon]] [[fisheries]] rely on the bay as a nursery. The few remaining [[salt marsh]]es now represent most of California's remaining salt marsh, supporting a number of endangered [[species]] and providing key [[ecosystem services]] such as filtering pollutants and [[sediment]]s from the rivers. San Francisco Bay is recognized for protection by the [[California Bays and Estuaries Policy]], with oversight provided by the [[San Francisco Estuary Partnership]].<ref name="swrcb">State Water Resources Control Board ''Water Quality Control Policy for the Enclosed Bays and Estuaries of California'' (1974) State of California</ref>

Most famously, the bay is a key link in the [[Pacific Flyway]]. Millions of [[waterfowl]] annually use the bay shallows as a refuge. Two [[endangered species]] of birds are found here: the [[California least tern]] and the [[Ridgway's Rail]]. Exposed [[bay mud]]s provide important feeding areas for [[shorebird]]s, but underlying layers of bay mud pose geological hazards for structures near many parts of the bay perimeter. San Francisco Bay provided the nation's first wildlife refuge, Oakland's artificial [[Lake Merritt]], constructed in the 1860s, and America's first urban National Wildlife Refuge, the [[Don Edwards San Francisco Bay National Wildlife Refuge]] (SFBNWR) in 1972. The bay is also plagued by non-native species.{{citation needed|date=April 2024}}

Salt produced from San Francisco Bay is produced in [[salt evaporation pond]]s and is shipped throughout the Western United States to bakeries, canneries, fisheries, cheese makers and other food industries and used to de-ice winter highways, clean kidney dialysis machines, for animal nutrition, and in many industries. Many companies have produced salt in the bay, with the [[Leslie Salt Company]] the largest private land owner in the [[San Francisco Bay Area|Bay Area]] in the 1940s.<ref>{{cite web| url = http://www.stanford.edu/group/spatialhistory/cgi-bin/site/pub.php?id=49| title = Spatial History Project<!-- Bot generated title -->| access-date = August 10, 2013| archive-date = May 21, 2013| archive-url = https://web.archive.org/web/20130521002410/http://www.stanford.edu/group/spatialhistory/cgi-bin/site/pub.php?id=49| url-status = live}}</ref><ref>{{cite web| url = http://arch.ced.berkeley.edu/hiddenecologies/?p=82| title = Hidden Ecologies » Blog Archive » Arden Salt Works<!-- Bot generated title -->| date = November 17, 2005| access-date = August 10, 2013| archive-date = October 16, 2015| archive-url = https://web.archive.org/web/20151016033341/http://arch.ced.berkeley.edu/hiddenecologies/?p=82| url-status = live}}</ref>

Low-salinity salt ponds mirror the ecosystem of the bay, with fish and fish-eating birds in abundance. Mid-salinity ponds support dense populations of [[brine shrimp]], which provide a rich food source for millions of shorebirds. Only salt-tolerant micro-algae survive in the high salinity ponds, and impart a deep red color to these ponds from the pigment within the algae protoplasm. The [[salt marsh harvest mouse]] is an endangered species endemic to the wetlands of the San Francisco Bay with a high salt tolerance. It needs native [[Salicornia|pickleweed]], which is often displaced by invasive cordgrass, for its habitat.<ref>{{Cite web|url=https://www.southbayrestoration.org/pdf_files/HarvestMouseHandout.pdf|title=Salt Marsh Harvest Mouse|website=South Bay Salt Pond Restoration Project|url-status=live|archive-url=https://web.archive.org/web/20170320233919/https://www.southbayrestoration.org/pdf_files/HarvestMouseHandout.pdf|archive-date=March 20, 2017|access-date=September 25, 2019}}</ref>

The seasonal range of water temperature in the bay is from January's {{convert|53|°F|°C}} to September's {{convert|60|°F|°C}} when measured at [[Fort Point, San Francisco|Fort Point]], which is near the southern end of the [[Golden Gate Bridge]] and at the entrance to San Francisco Bay.<ref>{{cite web| last = Osborn| first = Liz| url = http://www.currentresults.com/Oceans/Temperature/san-francisco-average-water-temperature.php| title = Average Ocean Water Temperatures at San Francisco| work = Current Results Nexus| access-date = October 19, 2013| archive-date = October 19, 2013| archive-url = https://web.archive.org/web/20131019134753/http://www.currentresults.com/Oceans/Temperature/san-francisco-average-water-temperature.php| url-status = live}}</ref>

For the first time in 65 years, [[Harbor porpoise|Pacific Harbor Porpoise]] (''Phocoena phocoena'') returned to the bay in 2009.<ref>{{cite news |title=Porpoises return to SF Bay – scientists study why |author=David Perlman |newspaper=San Francisco Chronicle |date=November 8, 2010 |url=https://www.sfgate.com/science/article/Porpoises-return-to-SF-Bay-scientists-study-why-3167006.php |access-date=July 25, 2011 |archive-date=November 5, 2011 |archive-url=https://web.archive.org/web/20111105013821/http://articles.sfgate.com/2010-11-08/news/24820859_1_harbor-porpoises-biologists-boston-whaler |url-status=live }}</ref> Golden Gate Cetacean Research, a non-profit organization focused on research on [[cetacean]]s, has developed a photo-identification database enabling the scientists to identify specific porpoise individuals and is trying to ascertain whether a healthier bay has brought their return.<ref>{{cite web |title=Harbor Porpoise Project |publisher=Golden Gate Cetacean Research |url=http://www.ggcetacean.org/Harbor_Porpoise.html |access-date=July 25, 2011 |archive-date=May 11, 2011 |archive-url=https://web.archive.org/web/20110511203115/http://ggcetacean.org/Harbor_Porpoise.html |url-status=live }}</ref> Pacific harbor porpoise range from [[Point Conception]], California, to Alaska and across to the [[Kamchatka Peninsula]] and Japan. Recent genetic studies show that there is a local stock from San Francisco to the Russian River and that eastern Pacific coastal populations rarely migrate far, unlike western Atlantic Harbor porpoise.<ref>{{cite report |title=Harbor Porpoise (Phocoena phocoena): San Francisco-Russian River Stock |publisher=[[National Marine Fisheries Service]] |date=October 15, 2009 |url=http://www.nmfs.noaa.gov/pr/pdfs/sars/po2009poha-rr.pdf |access-date=July 25, 2011 |archive-date=September 18, 2012 |archive-url=https://web.archive.org/web/20120918024442/http://www.nmfs.noaa.gov/pr/pdfs/sars/po2009poha-rr.pdf |url-status=live }}</ref>

The [[common bottlenose dolphin]] (''Tursiops truncatus'') has been extending its current range northwards from the [[Southern California Bight]]. The first coastal bottlenose dolphin in the Bay Area in recent times was spotted in 1983 off the [[San Mateo County, California|San Mateo County]] coast in 1983. In 2001, bottlenose dolphins were first spotted east of the Golden Gate Bridge and confirmed by photographic evidence in 2007. Zooarcheological remains of bottlenose dolphins indicated that bottlenose dolphins inhabited San Francisco Bay in prehistoric times until at least 700 years before present, and dolphin skulls dredged from the bay suggest occasional visitors in historic times.<ref>{{cite journal |title=Northern Range Expansion of California Coastal Bottlenose Dolphins (Tursiops truncatus) |author=William Keener |author2=Marc A. Webber |author3=Tim M. Markowitz |author4=Mark P. Cotter |author5=Daniela Maldini |author6=R. H. Defran |author7=Megan Rice |author8=Amanda J. Debich |author9=Aimée R. Lang |author10=Dennis L. Kelly |author11=Alex G. Kesaris |author12=Maddalena Bearzi |author13=Kayla Causey |author14=David Anderson |author15=Laurie Shuster |author16=David W. Weller |journal=Aquatic Mammals |year=2023 |volume=49 |issue=1 |pages=29–43 |doi=10.1578/AM.49.1.2023.29 |s2cid=255918023 |doi-access=free |bibcode=2023AqMam..49...29K }}</ref>