Lake Abert: An Irreplaceable, Ecological Gem

Ron Larson

Lake Abert is the only hypersaline lake in Oregon, one of three hypersaline lakes in the western U.S., and is the largest saline lake in the Pacific Northwest. This unique lake is vital habitat for hundreds of thousands of migratory birds traveling the Pacific Flyway, where they replenish their fat stores by feasting on alkali flies and brine shrimp that are adapted to live in this saline environment.

Read on below to find out more about what makes Lake Abert an irreplaceable, ecological gem.

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Sarah Graham, Sage Sustainers Member

Sarah Graham, Sage Sustainers Member

“I contribute to ONDA monthly because it adds up to a larger annual gift than what I’d be able to comfortably afford if I were to do a simple one-time donation annually. I’m able to give more to ONDA this way and have greater impact which is important to me, and my dog Polly.”

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Elisa Cheng, member since 2013

Elisa Cheng, member since 2013

“ONDA stewardship trips inspire me. I get to learn new things and see new places, and in the process perform important work that improves the wildlife habitat.”

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Wildflower Poetry Reading

Wildflower Poetry Reading

Ancient Lake Chewaucan once encompassed present-day Summer Lake and Lake Abert. Source: Ron Larson, redrawn after Grayson (1993)

In the cooler and wetter Pleistocene epoch (2.6 million years before present to 11,700 years before present), Lake Abert, Summer Lake, and the Chewaucan Marsh were once part of a larger Lake Chewaucan which was several hundred feet deep and covered 500 square miles. Evidence of this historic lake are visible in wave-cut terraces and cliffs and exposed depositional layers, including ash from Mt. Mazama which erupted approximately 7,000 years ago. As temperatures increased and precipitation levels declined in the Holocene starting around 10,000 years ago, Lake Chewaucan receded, creating the separate Lake Abert and Summer Lake and Upper and Lower Chewaucan Marshes.

Basin and Range faulting 7 million years ago produced the 15-mile elongated and shallow Lake Abert. During the Cenozoic period, the land in southeastern Oregon was stretched and expanded, nearly doubling in size. Thinning of the crust generated a series of faults, uplifting and tilting Abert Rim more than 2,500 feet over the down-dropped Lake Abert basin.

Lake Abert is a terminal or endorheic lake, meaning it is located within a closed basin with no outlet. All water that flows into the lake stays in the lake. Clay soils line the lakebed, eliminating water loss through leakage to the ground below. However, as summer temperatures rise the water evaporates, reducing the size of the lake and increasing water salinity. On average, 40 inches of water evaporate from the lake each year. Salts in the water are naturally derived from a variety of sources, such as dust and weathering of rocks. Millennia of this cyclical evaporation have accumulated high concentrations of salt in Lake Abert.

Although Lake Abert receives water input from four sources, all water leaves the lake through evaporation. Source: Ron Larson

Oregon has a number of saline lakes (lakes with salt concentrations greater than 0.3%). However, Lake Abert is Oregon’s only hypersaline lake (a lake with salt concentration greater than 5%), exceeding the ocean salinity of 3.5%. Lake Abert, and all saline lakes in Oregon, are also classified as alkaline lakes because they have a pH above 7, the neutral value of water.

Lake Abert’s primarily water source is the Chewaucan River which originates in the Fremont-Winema National Forest near Gearhart Mountain. The river is fed by snowpack and several tributary streams, including Crooked Creek near the lake’s inlet, flowing 53 miles before terminating at Lake Abert. Coldwater, Juniper, and Poison Creeks—ephemeral streams that only have water flowing at the surface for a short period of time each year—discharge into the lake along its eastern shore while numerous springs and seeps around the lake edge contribute additional water input; additionally, precipitation falls directly onto the lake’s surface.

Located east of the present-day town of Paisley, the Lake Abert area boasts of a long history of use by Indigenous people. Artifacts, settlements, and petroglyphs dating back thousands of years in the Lake Abert Basin challenge the current understanding of the culture of the Chewaucan people.

Long before Europeans settled in North America, the Chewaucan Basin was home to Indigenous peoples whose descendants are part of the Confederated Tribes of Warm Springs, Burns Paiute Tribe, Klamath Tribes, and the Fort Bidwell Indian Community. Many Indigenous peoples live in Oregon’s high desert region today, including members of the Burns Paiute Tribe, the Confederated Tribes of Warm Springs (Wasco, Warm Springs and Paiute), the Klamath Tribes (Klamath, Modoc and Yahooskin) and the Fort McDermitt Paiute and Shoshone Tribe.

Numerous archaeological studies throughout the area have provided important insights into the history of human habitation in the Great Basin and North America. Luther Cressman was one of the earliest archaeologists to work in Oregon whose extensive work provided ground-breaking information about the prehistoric human occupation in the region. The discovery of 75 sagebrush sandals at Fort Rock, bones of megafauna–including camel and mastodon — stone tools containing DNA remnants, and seeds unearthed in the Paisley Caves in the late 1930s reveal valuable information about the climate and ecology of the area as well as the lifestyle and subsistence patterns of prehistoric peoples. Additional archaeological work conducted by Dr. Dennis Jenkins in the past twenty years has unearthed coprolites radiocarbon dated at over 14,000 years old. Southeastern Oregon is believed to be one of the oldest inhabited areas in the New World.

Invertebrates and Microorganisms

Although Lake Abert once supported freshwater fish and a diverse aquatic fauna, the highly salt-concentrated water is now inhospitable to all freshwater organisms. However, some invertebrate species have adapted to thrive in these saline conditions, two of which occur in great number at Lake Abert: brine shrimp and alkali flies.

Female (top) and male (bottom) adult brine shrimp. Photos: Ron Larson

Brine shrimp (Artemia franciscana) are small crustaceans — distantly related to crabs, lobsters, and shrimp — only found in saline lake ecosystems. (They’re also the inspiration of the novelty Sea-monkeys product marketed beginning in the 1950s.) The shrimp feed, swim, and breath simultaneously utilizing their pleopods — feather-like appendages that move them through the water in a wave-like motion scooping water from their head to rear. When salinity levels are optimal, females release fertilized eggs into the water that hatch inside the brood sac or shortly after being released and reach maturity in as few as eight days. However, when salinity is high or oxygen levels are low, females release partially-developed embryos called cysts, which float on the water and collect along the lake shore. Cysts remain dormant in a state called cryptobiosis through extreme heat and cold and desiccated conditions until the lake reaches lower salt concentrations.

Dense concentrations of alkali flies form fly mats on the eastern shore of Lake Abert. Photos: Ron Larson

In good conditions, alkali flies (Ephydra hians) along the shoreline and floating on the water appear like dense, black patches resembling tar. Although similar in appearance to a house fly, alkali flies are only found at salty lakes in North America. Eggs are laid in the water by adult females which hatch within one to two days into larvae that move to mud substrates to feed on algae and bacteria. The larvae contain a specialized organ called a lime gland that removes excess salt from their body absorbed as they breathe through their skin. In the summer and fall, larvae grow hard shells and become pupae within a few weeks to one month, attaching to rocks or other floating organisms for several weeks while the adult develops inside. During colder temperatures, larvae remain dormant, waiting for warmer temperatures in the spring or early summer to transition to the pupal stage. Once the fly hatches, adults feed and mate, living less than a week.

Microbes, such as phytoplankton and bacteria, including cyanobacteria, provide food for alkali fly larvae and brine shrimp. Archaea or haloarchaea are very primitive unicellular microbes that occur in the lake under extreme salinities and contain a red pigment. They are halophilic (or salt-loving) organisms that require high salinities to live, lying dormant in the lake until salinity reaches 20-25%. Archaea can even survive salinities up to 30%, the concentration at which table salt forms. Also found in Lake Abert is a thread-like green alga (Ctenocladus circinnatus). This species is most productive when salt concentrations range between 2.5 and 7%, with few individuals found in concentrations of 15% or higher. The decomposition of the large biomass of Ctenocladus produces organic compounds that are used by bacteria.

Birds

More than 80 species of waterbirds have been observed at Lake Abert during migration along the Pacific Flyway. When conditions are optimal and brine shrimp and alkali fly populations are thriving, Lake Abert can support hundreds of thousands of birds whose arrival at the lake coincides with peak invertebrate populations. These abundant food sources, in addition to the shallow shoreline, unobstructed sight lines to avoid predation, and freshwater springs around the lake for bathing and drinking combine to create an ideal seasonal habitat for birds. In fact, it’s estimated Lake Abert supports more than 3 million bird-use days annually — the number of birds present in a 24-hour period multiplied by the number of days. Only the Great Salt Lake surpasses Lake Abert in importance to migratory species.

Large numbers of birds are attracted to the lake because of its abundant food supply. The numbers of brine shrimp in the lake has been estimated to be 300 billion individuals — totaling more than the weight of an adult blue whale — and alkali flies may be similarly numerous. The incredible food supplies are crucial to fuel migrating species on their journeys between Alaska and South America. Among the many birds that call Lake Abert home are Western snowy plover, Wilson’s phalarope, American avocet, and eared grebe.

A male snowy plover scans for insects along the Lake Abert shoreline. Photo: Ron Larson

While being less common along the Oregon coastline, most Western snowy plover migrate and breed throughout the Great Basin, including at Lake Abert. Typically foraging alone, snowy plovers feed by scanning the shoreline for invertebrates such as beetles and alkali fly larvae, quickly running to grab prey once spotted. Plover nests are inconspicuous depressions in the sand or alkali crusts, making them particularly susceptible to predation and disturbance by human activity, especially along the Oregon coast where the bird is listed as a federally threatened species. Although only approximately 333 snowy plover breed at Lake Abert, this accounts for nearly one-third of the interior population in Oregon.

Wilson phalarope looks for prey while vortex feeding. Photo: Ron Larson

Wilson’s phalarope is the most abundant waterbird observed at Lake Abert, where approximately one-fifth of the global population stop on their journey to South America. This small bird forages along the shore and in shallow waters by pecking at food on the surface with their long beak, or in vortex feeding in which the bird rapidly swims in circles in deeper water to bring plankton closer to surface, spinning in a full circle every second. While at Lake Abert, phalaropes molt and gorge themselves on shrimp and flies, nearly doubling in size before continuing their migration. Female phalaropes are larger and more colorful during the breeding season, easily identified by their rust-colored throat; males alone incubate the eggs and rear the young. Some phalaropes briefly visit Lake Abert in the spring before leaving to nest at nearby marshes. Female phalaropes arrive at the lake first in late July followed by the males and juveniles, regularly amounting to more than 100,000 birds. The highest count of Wilson’s phalaropes at Lake Abert was 330,000 birds.

An American avocet forages for alkali flies in the mud. Photo: Ron Larson

American avocet is one of the earliest birds to arrive at Lake Abert in the spring and one of the last to depart in the fall. Avocet populations peak in late summer and early fall, typically numbering over 5,000 birds with the highest recorded count in September 1993 of 40,000 birds. Because female and male avocets have similar breeding plumage, sexes are generally differentiated based on the shape of their bill, with females having greater upward curvature. Although some avocets do breed at Lake Abert — the largest breeding population estimate is 1,000 birds — most stop at the lake after breeding before heading to wintering sites in coastal Mexico and California.

Eared grebes were historically hunted for their prized golden plume and black crests. Photo: Ron Larson

Once extensively hunted for their colorful plumage, eared grebe populations have recovered and are regularly observed at Lake Abert throughout the spring and summer. As many as 40,000 birds have been counted at the lake in one month, with the highest abundances in late summer. Grebes nest in marshes where aquatic vegetation provides nesting material and cover, and primarily stop at Lake Abert to forage brine shrimp in great quantities and quickly gain weight during a process of “binge-eating” called hyperphagia during molt. Grebes internal organs and legs more than double in size while their pectoral muscles — crucial for flight — shrink nearly 50%, rendering them flightless for months. Several weeks before migrating south, grebes burn approximately one-third of the fat reserves gained during hyperphagia to rapidly reverse these physiological changes, regaining their ability to fly.

A western sandpiper wades in the shallow water of Lake Abert searching for food. Photo: Ron Larson

Next in abundance at Lake Abert is the western sandpiper with as many as 15,000 seen. Also known as peeps, along with four other North American sandpipers, the western sandpiper is a small shorebird weighing approximately an ounce, the equivalent of an AA battery. These birds breed in the Arctic and winter along the coasts of North and Central America, sometimes venturing a far south as Chile. Some peeps stop at Lake Abert in the spring on their way north to breeding grounds in Alaska but more concentrated numbers arrive in mid-summer. Western sandpipers eat by rapidly probing the ground in shallow water or along exposed shorelines, foraging for alkali fly pupae and other invertebrates.

Numerous other waterbirds utilize the food resources of Lake Abert, including American white pelican, black-necked stilt, western willet, red-necked phalarope, California gull, white-faced ibis, and northern shoveler. Upland bird species, such as loggerhead shrike, sage thrasher, rock wren, and horned lark, reside in the greasewood and sagebrush surrounding the lake while prairie falcon and golden eagle are commonly observed along Abert Rim. For a complete list of migratory and other bird species found on and around Lake Abert, see ONDA’s compilation which totals more than 200 species.

Lake Abert Storybook

To see more images of the incredible diversity of life at Lake Abert, flip through our storybook.

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Read on to learn about the problems Lake Abert faces and what ONDA is doing to save this invaluable ecosystem.

Lake Abert

For new articles, published science and links to additional information about Lake Abert, check out our Resources page.

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