Mono Lake

Mono Lake is a highly alkaline lake, or soda lake. Alkalinity is a measure of how many bases are in a solution, and how well the solution can neutralize acids. Carbonate (CO₃^2-) and bicarbonate (HCO₃⁻) are both bases. Hence, Mono Lake has a very high content of dissolved inorganic carbon. Through supply of calcium ions (Ca²⁺), the water will precipitate carbonate-minerals such as calcite (CaCO₃). Subsurface waters enter the bottom of Mono Lake through small springs. High concentrations of dissolved calcium ions in these subsurface waters cause huge amounts of calcite to precipitate around the spring orifices.[8] The tufa originally formed at the bottom of the lake. It took many decades or even centuries to form the well-recognized tufa towers. When lake levels fell, the tufa towers came to rise above the water surface and stand as the majestic pillars seen today (see Lake Level History for more information).

These are original sketches of thinolite made by Edward S. Dana from his book from 1884: Crystallographic Study of the Thinolite of Lake Lahontan.[9]

Description of the Mono Lake tufa dates back to the 1880s, when Edward S. Dana and Israel C. Russell made the first systematic descriptions of the Mono Lake tufa.[10][9] The tufa occurs as "modern" tufa towers. However, there are tufa sections from old shorelines, when the lake levels were higher. These pioneering works in tufa morphology are still referred to by researchers today and were confirmed by James R. Dunn in 1953. The tufa types can roughly be divided into three main categories based on morphology:[8][11]

• Lithoid tufa - massive and porous with a rock-like appearance
• Dendritic tufa - branching structures that look similar to small shrubs
• Thinolitic tufa - large well-formed crystals of several centimeters

These tufa types vary interchangeably both between individual tufa towers but also within individual tufa towers. There can be multiple transitions between tufa morphologies within a single tufa tower.

Through time, many hypotheses were developed regarding the formation of the large thinolite crystals (also referred to as glendonite) in thinolitic tufa. It was relatively clear that the thinolites represented a calcite pseudomorph after some unknown original crystal.[9] However, the original crystal was only determined when the mineral ikaite was discovered in 1963.[12] Ikaite, or hexahydrated CaCO₃, is metastable and only crystallizes at near-freezing temperatures. It is also believed that calcite crystallization inhibitors such as phosphate, magnesium, and organic carbon may aid in the stabilization of ikaite.[13] When heated, ikaite breaks down and becomes replaced by smaller crystals of calcite.[14][15] In the Ikka Fjord of Greenland, ikaite was also observed to grow in columns similar to the tufa towers of Mono Lake.[16] This has led scientists to believe that thinolitic tufa is an indicator of past climates in Mono Lake because they reflect very cold temperatures.

Rusell (1883) studied the chemical composition of the different tufa types in Lake Lahontan, a large Pleistocene system of multiple lakes in California, Nevada, and Oregon. Not surprisingly, it was found that the tufas consisted primarily of CaO and CO₂. However, they also contain minor constituents of MgO (~2 wt%), Fe/Al-oxides (.25-1.29 wt%), and PO₅ (0.3 wt%).

The red line represents the δ¹⁸O of a water mixture between lake water and riverine freshwater that depends on the fraction of lake water to riverine freshwater.

Carbon and oxygen isotopic compositions of Mono Lake tufas have the potential to reveal many interesting things about how water bodies mix in Mono Lake, how the climate changed throughout time in the Mono Basin, and how biology may or may not play a role in tufa formation. Steps have been made to understand the isotopic compositions of "modern" tufa and water isotopic composition in Mono Lake.

Mono lake water DIC has a δ¹³C composition of 2 ‰[17] (relative to PDB), and a δ¹⁸O of -0.1 ‰ (relative to SMOW).[18] Surrounding rivers feeding into Mono Lake have a δ¹⁸O of -14 to -17.5 ‰ and contains DIC with a δ¹³C composition of -14 ‰ .[18] We observe that both the δ¹³C and δ¹⁸O compositions of Mono Lake are enriched compared to surrounding water. One explanation for the enrichment of δ¹⁸O in Mono Lake water is evaporation. The lighter isotope (¹⁶O) will preferentially be evaporated, leaving more of the heavier isotope (¹⁸O) behind.

It is also important to note that tufa forms from a mixture between lake water and subsurface waters. Because the streams surrounding Mono Lake are depleted in δ¹⁸O compared to the lake water, combining the two sources will result in a water mixture that is more depleted than lake water. The figure above shows how δ¹⁸O of a water mixture changes with the fraction of lake water component. As the fraction of lake water decreases, the δ¹⁸O decreases.[19] The total CO₂ concentration (ΣCO₂) is much higher in the lake than in surrounding streams. Hence, this isotopic dilution effect is less significant for δ¹³C, and water mixtures should be dominantly composed of δ¹³C with lake water signatures.[19] In theory, Mono Lake tufa should have a δ¹³C composition reflecting the Mono lake water DIC composition, and a δ¹⁸O composition reflecting a mixture between Mono Lake and surrounding riverine water. This is only if we assume that the subsurface waters have similar compositions to riverine water.

There is also a temperature-dependent fractionation between Mono Lake water and precipitating carbonates. The clumped isotope composition (Δ47, representing the amount of ¹³C¹⁸O¹⁶O in the carbonate) of Mono Lake tufa are 0.734-0.735 ‰.[20] The temperature and δ¹⁸O of the corresponding water from which the tufa formed can be calculated using these Δ47-values[21] From these values, it is calculated that Mono Lake tufa formed at a temperature of ~15 °C in water. For δ¹⁸O, the calcite-H₂O fractionation is given by:

ε = 18.03(1000/T)-32.42[22] ~ -30‰ (SMOW)

For δ13C, the calcite-DIC fractionation is roughly given by:

ε ~ 1-2 ‰ (PDB) at 25 °C[23]

The calcite-aragonite fractionation is roughly given by:

ε ~ 2.7 ‰ (PDB) at 25 °C[23]

However, these fractionation effects do not account for salinity-dependency.

The δ¹⁸O values of modern tufas are 28–32.5‰, which reflects a corresponding water mixture composition of -2‰ to 2‰.[24][20] This range is similar to the composition of a mixture between Mono Lake and riverine waters. However, this mixture appears to be largely dominated by Mono Lake water.[24] Mono lake tufa have δ¹³C values that range from 5-8 for tufa of aragonitic composition[24] and 7-9‰ for tufa of calcitic composition.[20] These tufas are a little enriched compared to modern lake water DIC. As stated above, calcite/aragonite-DIC fractionation can only explain an enrichment of 1-3‰ compared to lake water, i.e. a tufa composition of 3-5‰. The reason for this small δ¹³C enrichment of tufa is still unclear and requires follow-up studies. It could be related to changes in DIC composition of Mono Lake, riverine water, and subsurface water compositions in the immediate past, which in turn could be related to climate or biological productivity in the lake. However, it could also be related to the fact that the isotopic composition of the subsurface waters that flow into Mono Lake is not well understood. These subsurface waters may have a very different composition compared to both Mono Lake waters and riverine surface waters. In addition, secondary crystallization (e.g. formation of calcite from aragonite) or meteoric diagenetic effects could have some control on the isotopic composition as well. Lastly, scientists may have to revisit the salinity-dependency of calcite/aragonite-DIC fractionation to understand whether this 1-3‰ fractionation may actually be larger in a lake with conditions similar to Mono Lake.

The covariation between δ¹⁸O in lake water and lake level in Mono Lake have been recorded over a 150-year time interval in Mono Lake.[18] The δ¹⁸O record was compared to historic lake levels recorded by the USGS. The lake level and δ¹⁸O record were observed to have a strong correlation with minor offsets. Changes in δ¹⁸O of lake water were inversely correlated with lake level. This revealed six stages in lake level in the past 150 years:[18] high stands at 1845, 1880, and 1915 as well as low stands at 1860, 1900, and 1933. The δ¹⁸O record compared well to the recorded precipitation and streamflow of Nevada City in California. Decreases in δ¹⁸O correlated well with increases in precipitation as well as increases in streamflow and vice versa.

A sediment core from Mono Lake reveals a 10,000 year record of carbonates (dated through ash beds).[19] Here δ¹⁸O and δ¹³C did covary when observed through long time intervals of >5,000 years, whereas the correlation was not present during shorter time scales. It was found that the record revealed 5 periods of distinct lake conditions:[18]

9.7 - 8.7 ka: Rising lake level. Decreasing δ¹⁸O and δ¹³C reflected an increased lake level. In fact, the lake level reached the Holocene High Stand. This high stand corresponded to a period of maximum effective moisture in the Great Basin.

8.7 - 6.5 ka: Dropping lake level. A sudden increase in δ¹⁸O and δ¹³C suggested that lake levels dropped. Following, weak correlation between δ¹⁸O and δ¹³C suggested that lake levels stabilized.

6.5 - 5.9 ka: Rising lake level. An increase in δ¹⁸O and δ¹³C correlated with a decrease in lake level. The lake level drop continued until the Holocene Low Stand at 5.9 ka, which corresponded to a period of minimum effective moisture in the Great Basin.

2 - 0.6 ka: Unconformity. The gap between 6 - 2 ka could be attributed to shallow lake conditions. In addition, sediment types observed in the core between 2 - 0.6 ka largely reflected shallow water conditions.[27] During the Medieval Warm Period, which occurred from 0.9 - 0.7 ka, the lake level was around the same as today.[27] In general, the period was dominated by a shallow, stable lake level with low covariance between δ¹⁸O and δ¹³C.

490 – 360 years ago: High, fluctuating lake levels. This period corresponded to the Little Ice Age. The isotopic record had very high annual resolution. The lake levels were generally high but fluctuated a little resulting in low correlation between δ¹⁸O and δ¹³C . At the end of this period, δ¹⁸O and δ¹³C evolved towards a trend of decreasing lake level.

Overall the lake levels of Mono Lake appeared to have corresponded to known climatic events such as periods of maximum or minimum effective moisture, the Medieval Warm Period_, and the Little Ice Age.

Lake levels of Mono Lake during the Pleistocene have also been reconstructed using stratigraphic inspection of paleoshorelines,[28] radio carbon dating,[29] and δ¹⁸O records from sediments.[29] These analyses helped reconstruct lake levels of the past 35,000 years.

36 - 35 ka: Rising lake level. Decreasing δ¹⁸O revealed that lake level began to rise at about this time from a lake level altitude of 2015 m.

35 - 21 ka: High stable lake level. Little fluctuation in δ¹⁸O suggested a stable lake level. This stable lake level corresponded to two beds of silt that would have been deposited in a deep lake.

20 - 15 ka: Dropping lake level. There was a sudden fall in lake level at the beginning of this period. Sand delta terraces from this time period indicated a lake-surface altitude of 2035 m.[28][29] Recorded δ¹⁸O increased over this time period, reflecting falling lake level.[29]

5 - 13 ka: Rising lake level. During this period, Mono Lake rose to its highest lake-surface altitude of 2155 m. This corresponded to a decrease in δ¹⁸O.

13+ ka: Dropping lake level. Following peak lake level, the lake level decreased to 1965 m at ~ 10 ka as evidenced by an increase in δ¹⁸O and paleoshorelines.

This lake-level record has been correlated with significant climatic events including polar jet stream movement, Heinrich, and Dansgaard-Oeschger events.

The reconstruction of lake levels through carbon and oxygen isotopes have revealed interesting results that can be correlated to dramatic changes in climate in the North Atlantic. In the recent past, Earth experienced periods of increased glaciation known as ice ages. This geological period of ice ages is known as the Pleistocene, which lasted until ~11 ka. Lake levels in Mono Lake can reveal how the climate fluctuated. For example, during the cold climate of the Pleistocene the lake level was higher because there was less evaporation and more precipitation. Following the Pleistocene, the lake level was generally lower due to increased evaporation and decreased precipitation associated with a warmer climate. Mono Lake reveals the climate variation on 3 different time scales: Dansgaard-Oeschger (repeats every 1,000 years), Heinrich (varying repetition), and Milankovich (repeats every 10,000 years).

From the compilation of δ¹⁸O data over the past 51,000 years from lakes throughout the Great Basin, including Pyramid Lake, Summer Lake, Owens Lake, and Mono Lake, it has been observed that changes in lake level can be correlated to Dansgaard-Oeschger events.[30] The δ¹⁸O records from these lakes showed oscillations in δ¹⁸O compositions of carbonates from these four lakes. Oscillation between high δ¹⁸O and low δ¹⁸O reflected cold/dry (low lake level with low precipitation) and warm/wet (high lake level with high precipitation) respectively. Read more about these isotopic effects in the Lake Level History section. Furthermore, total organic carbon (TOC) of the sediments from Pyramid Lake and Owens Lake were inversely correlated with δ¹⁸O and showed the same oscillations. TOC is often an indicator of the degree of biological productivity in a lake. This would suggest that high productivity correlated with a warm/wet climate at Mono Lake, while low productivity correlated with a cold/dry climate at Mono Lake. The timing of these oscillations matched the timing of Dansgaard-Oeschger events of the GISP2 core from 46 - 27 ka.[30] Minima in δ¹⁸O and maxima in TOC correlated with 11 different Dansgaard-Oeschger events. Dansgaard-Oeschger events are fluctuations in δ¹⁸O records from ice cores that repeat every 1,000 years. They are thought to be related to global climatic events. However, the exact causes for these fluctuations are still unresolved.

The lake level history of 36,000 years was investigated through correlations between δ¹⁸O records, radiocarbon dating, and paleomagnetic secular variation from Mono Lake sediments as described in the Lake Level History section.[31] Peaks in the δ¹⁸O records of Mono Lake sediments correlated with 3 Heinrich events known from the sea cores of the North Atlantic.[31] Heinrich events occurred when massive numbers of icebergs broke off from the ice sheets and fell into the North Atlantic.[31] These Heinrich events have been observed to correlate with peaks in δ¹⁸O compositions of carbonates globally. This pattern would generally indicate a global drop in temperature and a rising ice-volume. As water vapor moves from the equator to the poles, ¹⁸O is preferentially precipitated compared to ¹⁶O. When the water precipitates at the poles, it has a very depleted δ¹⁸O composition. Hence, ice sheets are vast reservoirs of ¹⁶O and have a very depleted δ¹⁸O composition. If the temperature dropped and ¹⁶O-containing ice-volumes grew, the remaining water bodies would experience a corresponding increase in δ¹⁸O composition. Three peaks in the δ¹⁸O records of Mono Lake may reflect 3 episodes of vast growth of the Pleistocene ice sheets that resulted in massive iceberg break-off at the ice-water interface.[31]

The δ¹⁸O records from Mono Lake sediments also exhibit trends over longer timescales of ~10,000 years. From 35 to 18 ka, the δ¹⁸O composition of Mono Lake sediments were gradually decreasing. This decreasing trend was inversely correlated with an increase in δ¹⁸O of sediments from a North Atlantic sea core.[31] This trend in δ¹⁸O suggested correlation with the southward movement of the polar jet stream from 35 to 18 ka.[31] As the polar jet stream moved southward, it caused increased precipitation of isotopically depleted rain water.[31][32][33] In turn, this caused Southern water bodies like Mono Lake to become isotopically depleted, while Northern oceans became isotopically enriched.[31][32][33] This movement of the polar jet stream was presumably caused by an increase in the Northern American ice sheet.[31][32][33] Two δ¹⁸O minima at 18 ka and 13.1 ka in Mono Lake sediments reflected two lake level high-stands of Mono Lake. These lake level high-stands presumably corresponded to two passages of the polar jet stream over Mono Lake that precipitated large amounts of rainwater with a depleted δ¹⁸O composition.[31] Following, the polar jet stream was forced south of Mono Lake.[31] Furthermore, the sudden reduction in Total Inorganic Carbon (TIC) during 26 - 14 ka could be attributed to the Tioga glaciation.[31] The Tioga glaciation would have caused a high in-flux of detrital materials to Mono Lake. As a result, the TIC in Mono Lake sediments would be lowered during this time period.

Large numbers of alkali flies at Mono Lake

Artemia monica, the Mono Lake brine shrimp

The hypersalinity and high alkalinity (pH=10 or equivalent to 4 milligrams of NaOH per liter of water) of the lake means that no fish are native to the lake.[37] An attempt by the California Department of Fish and Game to stock the lake failed.[38]

The whole food chain of the lake is based on the high population of single-celled planktonic algae present in the photic zone of the lake. These algae reproduce rapidly during winter and early spring after winter runoff brings nutrients to the surface layer of water. By March the lake is "as green as pea soup" with photosynthesizing algae.[39]

The lake is famous for the Mono Lake brine shrimp, Artemia monica, a tiny species of brine shrimp, no bigger than a thumbnail, that are endemic to the lake. During the warmer summer months, an estimated 4–6 trillion brine shrimp inhabit the lake. Brine shrimp have no food value for humans, but are a staple for birds of the region. The brine shrimp feed on microscopic algae.

Alkali flies, Ephydra hians live along the shores of the lake and walk underwater, encased in small air bubbles for grazing and to lay eggs. These flies are an important source of food for migratory and nesting birds.

8 Nematode species were found living in the littoral sediment:[40]

• Auanema spec., which is outstanding for its extreme arsenic resistance (survives concentrations 500 times higher than humans), having 3 sexes, and being viviparous.
• Pellioditis spec.
• Mononchoides americanus
• Diplogaster rivalis
• species of the family Mermithidae
• Prismatolaimus dolichurus
• 2 species of the order Monhysteridae

A female Audubon's warbler on tufa in the "South Tufa" area

Mono Lake is a vital resting and eating stop for migratory shorebirds and has been recognized as a site of international importance by the Western Hemisphere Shorebird Reserve Network.[41] Nearly 2,000,000 waterbirds, including 35 species of shorebirds, use Mono Lake to rest and eat for at least part of the year. Some shorebirds that depend on the resources of Mono Lake include American avocets, killdeer and sandpipers. Over 1.5 million eared grebes and phalaropes use Mono Lake during their long migrations.

Late every summer tens of thousands of Wilson's phalaropes and red-necked phalaropes arrive from their nesting grounds, and feed until they continue their migration to South America or the tropical oceans respectively.[2]

In addition to migratory birds, a few species spend several months to nest at Mono Lake. Mono Lake has the second largest nesting population of California gulls, Larus californicus, second only to the Great Salt Lake in Utah. Since abandoning the landbridged Negit Island in the late 1970s, California gulls have moved to some nearby islets and have established new, if less protected, nesting sites. Cornell University and Point Blue Conservation Science have continued the study of nesting populations on Mono Lake that was begun 35 years ago. Snowy plovers also arrive at Mono Lake each spring to nest along the remote eastern shores.

The indigenous people of Mono Lake are from a band of the Northern Paiute, called the Kutzadika'a.[42] They speak the Northern Paiute language.[43] The Kutzadika'a traditionally forage alkali fly pupae, called kutsavi in their language. Mono Lake was also referred to as Teniega Bah. The origin of the name "Kutzadika'a" is uncertain but could be a Yokut Native American term for "fly eater".[44]

The term "Mono" is derived from "Monachi", a Yokut term for the tribes that live on both the east and west side of the Sierra Nevada.[45]

During early contact, the first known Mono Lake Paiute chief was Captain John. He was also referred to by the Paiute names of Shibana or Poko Tucket. Captain John was the son of a Northern Paiute named 'older Captain John.'

The Mono tribe has two bands: Eastern and Western. The Eastern Mono joined the Western Mono bands' villages annually at Hetch Hetchy Valley, Yosemite Valley, and along the Merced River to gather acorns, different plant species, and to trade. The Western Mono traditionally lived in the south-central Sierra Nevada foothills, including Historical Yosemite Valley.[46]

Present day Mono Reservations are currently located in Big Pine, Bishop, and several in Madera County and Fresno County, California.

Mono Lake viewed from the summit of Mount Dana. Note near-landbridge at left, almost connecting Negit Island with the mainland shoreline.

Aerial view of Mono Lake in May 2019, with generous snow pack promising a good summer for the lake

The city of Los Angeles diverted water from the Owens River into the Los Angeles Aqueduct in 1913. In 1941, the Los Angeles Department of Water and Power extended the Los Angeles Aqueduct system farther northward into the Mono Basin with the completion of the Mono Craters Tunnel[47] between the Grant Lake Reservoir on Rush Creek and the Upper Owens River. So much water was diverted that evaporation soon exceeded inflow and the surface level of Mono Lake fell rapidly. By 1982 the lake was reduced to 37,688 acres (15,252 ha), 69 percent of its 1941 surface area. By 1990, the lake had dropped 45 vertical feet and had lost half its volume relative to the 1941 pre-diversion water level.[48] As a result, alkaline sands and formerly submerged tufa towers became exposed, the water salinity doubled, and Negit Island became a peninsula, exposing the nests of California gulls to predators (such as coyotes), and forcing the gull colony to abandon this site.

In 1974, Stanford University graduate student David Gaines studied the Mono Lake ecosystem, and he became instrumental in alerting the public of the effects of the lower water level.[49] The National Science Foundation funded the first comprehensive ecological study of Mono Lake, conducted by Gaines and undergraduate students from the University of California at Davis, the University of California at Santa Cruz, and Earlham College. In June 1977, the Davis Institute of Ecology of the University of California published a report, "An Ecological Study of Mono Lake, California," which alerted California to the ecological dangers posed by the redirection of water away from the lake for municipal uses.[49]

Gaines formed the Mono Lake Committee in 1978. He and Sally Judy, a UC Davis student, led the committee and pursued an informational tour of California. They joined with the Audubon Society to fight a now famous court battle, the National Audubon Society v. Superior Court, to protect Mono Lake through state public trust laws.[49] While these efforts have resulted in positive change, the surface level is still below historical levels, and exposed shorelines are a source of significant alkaline dust during periods of high winds.

Owens Lake, the once-navigable terminus of the Owens River which had sustained a healthy ecosystem, is now a dry lake bed during dry years due to water diversion beginning in the 1920s. Mono Lake was spared this fate when the California State Water Resources Control Board (after over a decade of litigation) issued an order (SWRCB Decision 1631) to protect Mono Lake and its tributary streams on September 28, 1994. SWRCB Board Vice-Chair Marc Del Piero was the sole Hearing Officer (see D-1631). Since that time, the lake level has steadily risen. In 1941 the surface level was at 6,417 feet (1,956 m) above sea level.[50] As of October 2013, Mono Lake was at 6,380.6 feet (1,945 m) above sea level.[50] The lake level of 6,392 feet (1,948 m) above sea level is the goal, a goal made more difficult during years of drought in the American West.

Mono Lake as seen from California State Route 120 (Mono Mills Road) on south

• In 1968, the artist Robert Smithson made Mono Lake Non-Site (Cinders near Black Point)[51] using pumice collected while visiting Mono on July 27, 1968 with his wife Nancy Holt and Michael Heizer (both prominent visual artists). In 2004, Nancy Holt made a short film entitled Mono Lake using Super 8 footage and photographs of this trip. An audio recording by Smithson and Heizer, two songs by Waylon Jennings, and Michel Legrand's Le Jeu, the main theme of Jacques Demy's film Bay of Angels (1963), were used for the soundtrack.[52]
• The Diver, a photo taken by Aubrey Powell of Hipgnosis for Pink Floyd's album Wish You Were Here (1975), features what appears to be a man diving into a lake, creating no ripples. The photo was taken at Mono Lake, and the tufa towers are a prominent part of the landscape. The effect was actually created when the diver performed a handstand underwater until the ripples dissipated.[53]

A scene featuring a volcano in the film Fair Wind to Java (1953)[54] was shot at Mono Lake. Most of the scenes in the 1973 movie High Plains Drifter starring Clint Eastwood were filmed on the south shores of the lake at Navy Beach.

The music video for glam metal band Cinderella's 1988 power ballad Don't Know What You Got ('Till It's Gone) was filmed by the lake.[55]

The original inner sleeve of Wish You Were Here (Pink Floyd album) features Mono Lake with a splash-less diver.

Mark Twain's Roughing It, published in 1872, provides an informative early description of Mono Lake in its natural condition in the 1860s.[56][57] Twain found the lake to be a "lifeless, treeless, hideous desert... the loneliest place on earth."[6][58]