Friends of the Dunes

Science & Nature

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Cultural History

Wiyot people have long lived around Wigi, or Humboldt Bay. This place was and still is, the center of their culture. For thousands of years, native people enjoyed the abundant and varied resources surrounding the bay. The Wiyot territory extends from Little River to Bear River and as far east as the prairies of Kneeland. Not long ago, Wiyot people used the dunes of the north and south spits to gather and hunt for what they needed in their daily lives, such as surf fish and various berries that were dried in the sun. Women would gather food and prepare weaving materials while the men would fish and make new tools to replace old ones.

By the mid 1800's, the quest for gold and timber brought settlers to the area seeking to make their fortune. Tragically, greed for land and resources led to brutal acts of violence against the Wiyot people. Violent clashes along with exposure to foreign diseases such as smallpox nearly annihilated native people. The newcomers displaced the Wiyot and changed the landscape around Humboldt Bay. Marshy areas were drained and diked for cattle pasture, and railroads were built to take logs out to waiting ships. Towns grew and people used the bay and coast mainly as a transportation hub for industry.

Canoe on Humboldt Bay

Today, Wiyot people still fish and gather in some areas around the bay, but land usage has changed, and many of the plants once collected are not in the abundance they once were. The Wiyot are actively involved in protecting areas for gathering as well as establishing economic, health and educational projects and revitalizing aspects of traditional culture such as language, ceremonies and the arts.

Natural History

Dune Geology

Dune Geology The key ingredients needed to build a dune system include a source of sand, a shoreline perpendicular to the prevailing winds and a low landscape over which dunes can migrate. In addition, plant species that are adapted to survive the drying winds and shifting sands are needed to help shape and build the dunes. Here in the Humboldt Bay area, the Mad and the Eel rivers supply most of the sand. Winter storms flood these rivers and transport sand to the ocean. Sand is carried by currents along the coast and pushed up on to the beach by gentle summer waves. Once dry, the sand is moved by the prevailing summer winds from the northwest. This dynamic process has created of a variety of dune habitats within a narrow stretch of coastline.

Dune Ecology

Photo by Andrea Pickart The waveslope is the area of the beach that shows evidence of having been washed by waves during the last tidal cycle. Beachcombing here you can find everything from eelgrass, pacific razor clam shells, sand dollars, to the carcass of a gray whale. This is also the feeding area for a number of shore birds. They feed on small invertebrates in the sand and in the seaweeds washed on shore. The upper end of the waveslope is the strand. Here you may find plants such as sea rocket and native dune grass starting to colonize the bare sands.

The series of dunes and ridges paralleling the beach are collectively called the foredunes. In areas that are relatively undisturbed by invasive species, you can find a unique community of plants referred to as the dune mat. Here, a wide array of wildflowers adapted to the drying conditions of the dunes help stabilize the shifting sand. The dune mat is home to two federally listed endangered plant species, the Humboldt Bay wallflower and the beach layia. Take care to stay on the main trails through these areas.

Hollows/Swales form when the summer wind has removed the sand down to the water table, allowing water-loving plants to move in. During winter storms the water table rises and forms seasonal ponds in these areas. Tadpoles of the pacific tree frog and red-legged frog can be found here. Eventually forests may develop in these areas.

Few plants can survive the open sands of moving dunes. Look for mammal tracks of nocturnal animals like gray fox, skunk and raccoon crossing from the different areas. In some places, you can see that these moving dunes are slowly covering the dune forest. Large beach pine and Sitka spruce create an area that is surprisingly different and diverse. Developed soils allow for thick plant growth, with huckleberry, silk tassel, red-flowering currant and salal. The forest is also home to many species of lichens, including puffy mats of reindeer lichens, more characteristic of northern forests.

Salt marshes and estuaries are recognized by biologists as among the most productive habitats in the world. The nutrient rich waters form the basis of the salt marsh food chain. Plants such as pickleweed and salt grass are specially adapted to tolerating the salty conditions of a tidal area.

Humboldt Bay

Physical Geography

Humboldt Bay

Humboldt Bay, known to Wiyot People as Wigi, is the second largest enclosed bay in California. It is14 miles long and 4.5 miles across at its widest point. The channel, approximately 30 feet deep, is located near the north end of the South Bay and connects the bay to the ocean providing daily interchanges of seawater. The bay consists of two wide but shallow northern and southern arms connected by a relatively narrow channel.

Arcata Bay, also called North Bay, is the larger of the two bay segments and covers a surface area of about 8,000 acres. Most of Arcata Bay is extremely shallow and about 4,500 acres of mudflats are exposed at low tide. The shallow mudflats are traversed with deeper channels formed by tributaries and erosion from tidal drainage. The South Bay is about 4,600 acres in size and is similar to Arcata Bay in character. It is also mostly shallow, and 2,400 acres of mudflats are exposed at low tide. In addition to abundant mudflats, lush eelgrass beds are located throughout the South Bay.

Humboldt Bay is an estuary, which is an area where saltwater and freshwater come together and mix. The bay receives most of its freshwater as runoff from a drainage area of approximately 288 square miles surrounding the Bay. The main tributary streams are: Jacoby Creek, Freshwater Creek, Elk River, and Salmon Creek. Many smaller streams also enter the Bay directly or by way of one of its tributary sloughs.


Humboldt Bay

The two main habitats of the Humboldt Bay are mudflats and eelgrass beds. Eelgrass (Zostera marina) is not an alga but an angiosperm (flowering plant). It grows mostly in shallow water bays and is the main food source for black brant and other waterfowl species. Eelgrass beds also serve as important habitat and nursery areas for many species, a lot of which are important for sport and commercial fisheries. Some species that use eelgrass beds during part of their life include lingcod, Dungeness crab, halibut, Cabazon, English sole, Pacific herring, and several species of near shore rock fish. There are also many animals that spend their entire life in the eelgrass such as bay pipefish, nudibranchs and sea hares. The bay is also home to some marine predators, including brown smooth hounds, leopard sharks, and seven gill sharks.

The intertidal mudflats of the bay are fully exposed at low tide, and entirely covered by water at high tide. Plant life on the mudflats consists of eelgrass, and several species of algae including sea lettuce (Ulva spp.), rockweed (Fucus sp.), and polysiphonia (a red alga). Invertebrates are abundant in the mudflats and many birds depend on them food. Most invertebrates occur in the top 6 inches of the mud with approximately 97% being found in the upper 2 inches. The species and numbers of invertebrates present are determined by the sediment composition and location in relation to tidal submergence time. Some invertebrates that burrow in the mudflats include polycheate worms, clams, ghost shrimp, and fat innkeeper worms.

The mud of the bay has a rotten egg odor, and that the yellow-brown color of the mud surface differs from the blackish color of the mud underneath. Beneath the thin surface layer, little oxygen can penetrate and bacterial respiration is anaerobic. The by-product, hydrogen sulfide, smells like rotten eggs. The hydrogen sulfide reacts with iron sulfide to produce hematite, which is yellow-brown.

Invasive dense-flowered cordgrass (Spartina densiflora) has infested an estimated 90% of salt marshes in Humboldt Bay and the adjacent Eel and Mad River estuaries. The invasion of Spartina threatens the natural diversity and structure of salt marshes in Humboldt Bay as well as other estuaries along the west coast. You can read more about Spartina and salt marsh ecology, restoration methods, the status of Humboldt Bay National Wildlife Refuge's two-year refuge eradication project, and links to other west coast and international Spartina eradication efforts at: Spartina Invasion and Management.

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