Elkhorn Slough

Elkhorn Slough is one of the more important, relatively unpolluted saline marshes on the central California coast. Approximately a tenth of the area is in open water or channels, 20% in mudflats, 50% in salt marshes, and the rest in dunes, beaches and saltponds.

Dominant plants in the marine zone are blue and green algae, with the green Enteromorpha the most common. In the upper part of the littoral zone is a typical salt marsh habitat with pickleweed, Salicornia, comprising over 90% of the vegetation. At the higher, outer edges of the marsh is the maritime zone with little tidal exposure; saltgrass, Distichlis spicata, and Frankenia grandifolia are common. Freshwater marshes with dense stands of bulrushes, Scirpus ssp., cattails, Typha ssp., and rushes, Juncus ssp., are found on tributaries.

While vegetation on the lower littoral mudflats is sparse, there is a wide variety of invertebrates such as crabs, snails, worms, clams, etc., which makes this area very attractive to birds.

Shorebirds and waterfowl are observed throughout the year, with peaks during the migratory seasons. Over 90 species of water-associated birds have been reported, with shorebirds dominating. Several endangered species utilize the slough: the California clapper rail, Rallus longirostris obsoletus, nests here; the California brown pelican, Pelecanus occidentalis californicus, roosts here, and the California least tern, Sterna albifrons browni is a casual visitor.

Some 70 species of fish have been found in the area, 48 in the slough proper. It is the nursery for a number of marine fish as well as estuarine species. The bottom and mudflats support an exceptional, rich assemblage of invertebrates including 28 species of clams, 8 species of shrimp, 12 types of crabs, etc.

Geologically the slough is only recently saline, having been a freshwater lagoon at the mouth of the Salinas River before the river changed its course in 1908 to debouch some 8 kilometers (5 miles) south. In the late Pleistocene, less than 100,000 years ago, the slough was a part of the Pajaro River which drained Lake San Benito and later Lake San Juan. Elkhorn Slough stands at the head of the Monterey Submarine Canyon, one of the deepest in the world.

Integrity: Saltponds, dredging, industrial and commercial building have considerably altered the area near the ocean, and though some of the salt marsh has been "reclaimed" for grazing, much of the inland area retains a relatively pristine aspect.

Use: Research, education, sport fishing, clamming, hunting. The area has been intensively studied for over 70 years and is used by numerous universities, colleges and other schools. The Moss Landing Marine Laboratory is located here.

Ref: Browning, Bruce, et al, 1972. The Natural Resources of Elkhorn Slough, California Department of Fish and Game, Sacramento, Calif. (Bibliography)
MacGinitie, George E., 1935. Ecological Aspects of a California Marine Estuary. Am. Midi. Nat. Vol. 16 (5), p. 629-765.

January 1975