At Moss Landing, Highway 1 crosses over Elkhorn Slough, one of the largest estuaries in California. Estuaries are places where the sea meets freshwater. They are home to a rich array of plants and animals that can live in this unique habitat. At Elkhorn Slough, the seawater enters the estuary at the harbor mouth directly west of the Highway 1 bridge, and freshwater comes from several sources: the Salinas River; Tembladero Slough, which runs south of Castroville; and upland creeks that feed into both Moro Cojo and Elkhorn sloughs.

People have lived along the shores of Elkhorn Slough for at least 8,000 years. Successive waves of people have used the slough in different ways, including harvesting shellfish, fishing, hunting, agriculture, and even helping to generate electrical power. Conservation work in the last few decades has protected much of the natural habitat at Elkhorn Slough and has restored areas that were impacted by earlier human uses.

Today, it is one of the largest and most ecologically important estuarine systems in California. It provides habitats for native shorebirds, marine mammals such as sea otters and sea lions, and a wide variety of marine invertebrates. The slough also serves as an important nursery for a variety of fish species.

Habitats and Wildlife at Elkhorn Slough

Elkhorn Slough tidal habitats encompass extraordinary biological diversity, providing critical habitat for more than 135 aquatic bird, 550 marine invertebrate, and 102 fish species. The slough is also home to sea lions, harbor seals, and California sea otters. More than 200 different bird species use the slough as a resting spot during their annual migrations.

The upland habitats within the watershed include three of the top 10 most imperiled US habitats: freshwater wetlands, coastal prairie, and maritime chaparral. These systems are amazingly diverse, with coastal prairie being the most species-rich grassland in North America.

Along with providing habitat for a diverse range of life, wetlands provide a critical service to the environment. They provide a buffer between land and sea, which protects the water from soil erosion and protects the land by reducing the impact of flooding. As natural filters, wetlands can remove impurities from the water before they enter our streams and oceans.

Estuaries like Elkhorn Slough are among the most threatened ecosystems in California, facing rates of habitat loss between 75 and 90 percent. As a result, a disproportionate number of rare, threatened, and endangered species reside in these areas. In the Elkhorn Slough watershed, two dozen species are included in these categories. Because experts recognize the value of these resources to the country, the National Oceanic and Atmospheric Administration (NOAA) designated areas of Elkhorn Slough as part of the Monterey Bay National Marine Sanctuary and as a National Estuarine Research Reserve.

Moss Landing Harbor

The estuary habitats were profoundly affected by the creation of the present day Moss Landing Harbor. In 1947, just two years after the end of World War II, the Army Corps of Engineers dredged a channel through the barrier dunes for a new harbor entrance.

World War II had greatly restricted commercial fishing, so when the war was over, development of a commercial fishery in the area became a priority. An opportunity to increase access to fertile fishing areas in Monterey Bay was realized by expanding the harbor at Moss Landing. Today, Moss Landing Harbor is a center for commercial and recreational fisheries, public boating tours of the Monterey Bay and the Elkhorn Slough, kayaking, and world-renowned ocean research facilities.

Changes to the mouth have had ripple effects up the slough. The main slough channel has continued to widen and deepen since it was first dredged decades ago. Scientists at the Elkhorn Slough Reserve are currently studying the long-term effects of these changes.

Take the Self-Guided Mobile Tour

This piece is part of the Santa Cruz Marine Protected Areas Beaches Tour made possible by the Santa Cruz Collaborative with support from the California Marine Sanctuary Foundation and the Resources Legacy Fund. Download the free app with many tours of the Santa Cruz area and beyond.