[MUSIC]

I'm Erika Zavaleta and this is Ecosystems of California, and

I'm at Mono Lake in the eastern part of California in the great basin.

Mono Lake is one of many closed basin lakes and the great basin and

by closed basin I mean a lake that has no surface or sub-surface outflows.

So water that comes into the lake doesn't have anywhere to go but

into the atmosphere, it eventually have reevapolate, and

what that means is at least behind everything dissolved in it.

A lot of salt, a lot of sodium, but also bicarbonate and carbonite.

And as a result, the lake is about three times as salty as the ocean, and

it has a very alkaline pH, it has a pH of about ten.

That yields a really, really unique ecosystem in the lake.

So quick overview of where we are.

You can see behind me the high peaks of the southern Sierras and

then coming down from that you can see the lake itself.

Right behind me are the islands and the lake.

The largest of the Aroha Island Is still isolated from the mainland and

it has been for a long time.

There's a smaller island.

Nidgit Island in front of it, that's a little bit darker.

And that smaller island at one time became connected to the land through a land

bridge because of lowered lake levels.

Both the salinity and the water level of the lake are really sensitive

to climate and other inputs, because it is a closed basin lake.

And so, over its 500,000 year or more history, lake levels and

salinities have fluctuated a lot.

In the late Pleistocene, during the period of maximum glaciation,

this lake was really, really deep compared to what it is now.

It was about 300 meters deep, and from the air you can see the old bathtub ring

of that very, very large Pleistocene lake level.

More recently, in the last millennium because of prolonged droughts,

the lake level dropped quite a bit.

And then the most serious changes in the lake's level and

salinities have occurred just in the last 75 years, and the reason for

that is a long and complicated story.

John Muir, the famous preservationists first visited Mono Lake

as a side trip from Tuolumne Meadows up in Yosemite to our west In 1869.

And at the time he was so taken with the lake that he battled for

the park boundaries to actually include parts of Mono Lake.

In the end, the park boundaries stayed well up slope and west of here.

And the history of Mono Lake took a really different turn.

One of his contemporaries in the early 20th century WIlliam Moholland

was a passionate engineer and

he took on the project of delivering water to Los Angeles which was then growing

rapidly as a city in southern California without a lot of nearby water supplies.

So Mono Lake even though it's 338 miles from Los Angeles.

Well over 500 kilometers was the target of some of his energy.

In 1914 diversions not from the lake itself which is much too salty to use but

from the creeks that feed Mono Lake in the sierras began and

that water was transported to Los Angeles.

Because there were no surface flows coming into the lake, between 1941 and

the early 1980s, the lake level dropped by over 14 meters, or about 45 feet.

And that doubled the solidity of the lake and

exposed all of these tufa towers that you see around me.

And exposed parts of the islands in the middle of the lake as well.

One of the islands, Nidgit Island, which as been a significant breeding area for

seabirds, including California gulls and and

some other species, was actually connected to the mainland by a land bridge,

because of the lowered lake levels.

And so predators, like foxes could get out on the island, and

they destroyed the breeding colony.

The tufa towers that you see all around me are formed under water.

They're formed when calcium-rich waters from underground springs bubble up,

they encounter the carbonate rich waters of the lake.

And then calcium carbonate forms which is basically limestone.

So these are limestone towers that formed gradually in a creek over

these underwater springs over a really, really long period of time.

All of the ones you see are exposed because of lake levels having been lowered

since 1941.

In the 1980s,

a group of concerned citizens launched the Mono Lake Research Group,

which looked at the effects of all of those water diversions on lake ecology and

started a movement to obtain legal protections for the lake.

And they were able to use that information to secure legal protections for

the lake's water levels.

So since the 1980s,

the water levels in this lake have come back up almost two meters.

And that's because Los Angeles now has to limit its withdrawals from Rush and

Lee Vining Creek.

The way that that system works is that waters flowing down Rush Creek and

Lee Vining Creek that would reach the lake, are instead diverted

to a storage facility from which they make their way to Los Angeles.

And the diversions to that storage facility now

are regulated to maintain levels of the lake.

And for it's part the Department of Water and Power in the City of Los Angeles

have gone to great lengths to conserve water In order to be able

to meet their needs without withdrawing so much water from Mono Lake.

So, they have a goal of reducing withdrawals by 20% by the year 2017 and

by 50% by the year 2024.

There were combination of conservation measures Water recycling,

storm water capture and creative incentives like payments

of $3.75 a square foot for people to remove lawns.

In spite of all these protections,

The future of the lake remains unclear because climate change is both increasing

the temperature which is increasing the evaporative demand from the lake and

then potentially reducing inputs by reducing precipitation in the Sierras that

feed the lake, so even with those protection measures and

even with conservation by Los Angeles even if withdrawal stopped

it's possible that lakes levels would continue to drop over the next century.

Because of the history of the lake it's extremely well studied and

the ecology of Mono Lake is singular because of its unusual

chemistry in particular it contains a lot of organisms with adaptations and

strategies that go back to the very, very early history of life on Earth.

So at the very base of this lake's energy and

matter transfers are a huge variety of microbial organisms.

And because the lake is deep, it has real strong, seasonal and vertical variation in

chemical conditions and the availability of nitrogen, and phosphorous, and oxygen.

Deeper in the lake are microbe's that use both anaerobic and

aerobic pathways to fix carbon and because the lake has high levels of

arsenic there are also microbes adapted to use arsenic.

Either as arsenide or as arsenate as part of a process of chemophototsynthesis.

So rather than using light to photosynthesize and produce energy,

they're using methane and

or arsenic as part of the pathway to producing fixed carbon.

They break down detritus in the lake and are consumed

by enormous numbers of brine shrimp that hatch out seasonally in the spring and

become really abundant in the summer and the shrimp die at the end of

every summer and their bodies contribute to the nitrogen content of the lake.

Alkali flies are the other organism that occur in huge abundance and

feed on some of the primary production, the algae that grow in the lake.

And those alkali flies historically were an important food source for

indigenous people around here.

Not the flies themselves but the pupae that they lay underwater.

So they lay eggs underwater.

Adult flies can actually store air for about 15 minutes,

they can take an air bubble with them, dive down, lay their eggs.

And the eggs hatch, pupae form,

and those pupae are like little buttery, crunchy snacks that indigenous people

here used to eat in large numbers because there are so many of them.

Those hatch out, the adult flies emerge, and the cycle repeats itself.

Above the flies and the brine shrimp are enormous numbers of birds

that come here to consume them seasonally, mostly migratory birds.

There are over a million, for instance, eared graves that come through Mono Lake

every year and depend on the production of brine shrimp, called Artemia in the lake.

And then there are also breeding birds and birds that resident year around here.

It's a variety of things, and gulls and a variety of other shorebirds and seabirds.

They form the top of the food web.

There are no fish in this lake.

They've never been here as far as we know, so it's a simple food web.

To a little microbes, algal primary productions algae, flies and

shrimp and birds.

California's lakes are all different and Mono Lake is completely unique

in the state for its ecology as a highly salient closed based in lake.

But it's an important part of the state history and

an important feature of its landscape.

[MUSIC]

Mono Lake

Ecosystems of California

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