Elkhorn Slough is a tidal

slough Slough () is a town in Berkshire, England, in the Thames Valley, west of central London and north-east of Reading, at the intersection of the M4, M40 and M25 motorways. It is part of the historic county of Buckinghamshire. In 2021, the ...

and

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area. San Francisco itself is further north along the coast, by about 75 miles (120 km), accessible via California S ...

Monterey County, California Monterey County ( ), officially the County of Monterey, is a county (United States), county located on the Pacific Ocean, Pacific coast in the U.S. state of California. As of the 2020 United States census, its population was 439,035. The count ...

. It is California's second largest estuary and the United States' first estuarine sanctuary. The community of

Moss Landing Moss Landing, formerly Moss, is an unincorporated community and census-designated place (CDP) in Monterey County, California, United States. It is located north-northeast of Monterey, at an elevation of . It is on the shore of Monterey Bay, at t ...

and the

Moss Landing Power Plant The Moss Landing Power Plant is a natural gas powered electricity generation plant as well as a battery energy storage facility, located in Moss Landing, California, United States, at the midpoint of Monterey Bay. , the site's battery stor ...

are located at the mouth of the slough on the bay. The

Elkhorn Slough National Estuarine Research Reserve The Elkhorn Slough National Estuarine Research Reserve is a nature reserve that is located at 1700 Elkhorn Road in Watsonville, California, Watsonville, California. The reserve encompasses the central shore of Monterey Bay and is approximately ...

and Elkhorn Slough State Marine Conservation Area (SMCA) are in the area. Elkhorn Slough harbors the largest tract of tidal

salt marsh A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. I ...

in California outside the

San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...

and provides much-needed habitat for hundreds of species of plants and animals, including more than 340 species of birds. It has been designated as a protected

Ramsar site A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention,8 ha (O) *** Permanent 8 ha (P) *** Seasonal Intermittent < 8 ha(Ts) **

History

The name of the slough derives from the native

tule elk The tule elk (''Cervus canadensis nannodes'') is a subspecies of elk found only in California, ranging from the grasslands and marshlands of the Central Valley to the grassy hills on the coast. The subspecies name derives from the tule (), ...

''Cervus canadensis nannodes'', now extirpated from the region. Elkhorn Slough occupies the western reaches of Elkhorn Valley, a relic river valley eroded by drainage pouring out of the Santa Clara Valley and/or Great Valley of California (before the

Golden Gate The Golden Gate is a strait on the west coast of North America that connects San Francisco Bay to the Pacific Ocean. It is defined by the headlands of the San Francisco Peninsula and the Marin Peninsula, and, since 1937, has been spanned by ...

opened) into Monterey Bay during the early Pleistocene. In the mid-1850s A.D. Elkhorn Slough was a minor tributary to the much larger Pajaro-Salinas River system which shared a common entrance to the Pacific Ocean north of Moss Landing. In 1909 winter storms modified the course of the Salinas River to its present location south of Moss Landing, while Elkhorn Slough persisted as a tributary to the Old Salinas River channel. Construction of jetties at the Moss Landing Harbor in 1946 provided a direct link between the Pacific Ocean and Elkhorn Slough. At this time, salt marshes began to retreat from the axis of Elkhorn Slough as it evolved into its present form as a relatively stable estuarine embayment.

Watershed

Carneros Creek is the primary source of freshwater flowing into Elkhorn Slough. McClusky Slough to the north and Moro Cojo Slough to the south also provide freshwater inputs.

Habitat and wildlife

Elkhorn Slough, one of the largest

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

in California, provides essential habitat for over 700 species, including aquatic

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s, birds, fish,

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

alga Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

e and plants. The slough area is home to California's greatest concentration of

sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern Pacific Ocean, North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of ...

s, as well as populations of

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

Santa Cruz long-toed salamander The Santa Cruz long-toed salamander (''Ambystoma macrodactylum croceum'') is an endangered subspecies of the long-toed salamander, which is found only close to a few isolated ponds in Santa Cruz County, California, Santa Cruz and Monterey County ...

and the

threatened A threatened species is any species (including animals, plants and fungi) which is vulnerable to extinction in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensatio ...

California red-legged frog The California red-legged frog (''Rana draytonii'') is a species of frog found in California (USA) and northern Baja California (Mexico). It was formerly considered a subspecies of the northern red-legged frog (''Rana aurora''). The frog is an I ...

. The population of sea otter living in Elkhorn Slough reflect that the species is well-adapted for estuarine habitat, and may be a model for the historical sea otter populations now extinct in

. Elkhorn Slough hosts year-round residents tightly associated with estuaries, such as

pickleweed Pickleweed is a common name used for two unrelated genera of flowering plants: *'' Batis'', family Bataceae *''Salicornia ''Salicornia'' is a genus of succulent, halophytic (salt tolerant) flowering plants in the family Amaranthaceae that grow i ...

eelgrass Eelgrass is a common name for several plants and may refer to: * '' Zostera'', marine eelgrass * '' Vallisneria'', freshwater eelgrass See also *'' Potamogeton compressus'', known as eel-grass pondweed {{Short pages monitor