Sea Monkeys!! (Brine Shrimp of Mono Lake)

Mono Lake, an otherworldly spot east of the Sierra Nevada in California's Great Basin desert, is such a fascinating place in so many ways, I could spend days reading and writing about it.  The geological history of the area is rich: Mono Lake, a salty inland sea with no outlet, sits in a fault basin and was formed from the melting of glaciers during the last ice age.  The glacial history written in the bordering mountains and the volcanic history seen in nearby craters, Mammoth Mountain, the Long Valley Caldera, and islands in Mono Lake itself are all worthy topics of study in their own right.  And the lake's famed tufa towers certainly deserve the spotlight in an article of their own, as do my beloved plants - in this case, those plants that have evolved to tolerate not only harsh desert conditions, but extreme salinity and alkaline soils as well!  The wonders are new every morning at Mono Lake! 

Shoreline at Mono Lake's South Tufa Area
 
Political struggles surrounding the lake have been quite fierce.  The lake is fed by streams flowing from the Sierra Nevada, but water was diverted from these streams and sent to water the landscapes and booming population of Los Angeles beginning in 1941.  As a result, lake levels dropped 45 vertical feet.  (That is a story for another day; suffice to say that for now, at least, while the future of the lake is not entirely secure, conditions are an improvement on what they have been.)
 
But today, I'm more interested in discussing the ecology of Mono Lake, focusing on one of its most famous inhabitants: the sea monkey.
 
Little greenish brine shrimp, each about 0.4 inches long.

Brine Shrimp (yes, they really are the very same critters sold in shops under the name "Sea Monkeys") form an integral part of Mono Lake's food web.  The lake boasts its own unique species of brine shrimp, Mono Lake Brine Shrimp (Artemia monica), an enchanting, translucent-greenish little crustacean.  The salty, alkaline lake waters absolutely teem with billions of these little guys; estimates put their numbers around 5 trillion during the summer months.  And insignificant though they may seem, the ecosystem would collapse without them.
 
The lake initially appears "dead" and desolate to any casual observer, and it's true that the ecosystem found here really is comparatively simple, with just a few key species.  But the lake is far from a "dead sea" and the species that do survive here are present in massive numbers, which makes all the difference. 
 
Brine shrimp in a shallow disc (ok, it's a Frisbee).  They're barely visible in the photo above, but you can see one where
the finger is pointing.  This gives a sense of just how tiny brine shrimp are.

The ecosystem of Mono Lake is a great teaching tool for illustrating the concept of a simple food web.  The entire ecosystem is based on three key species: algae, alkali flies, and brine shrimp.  Green algae is photosynthetic, using the sun's energy to grow and obtaining nutrients from the lake water.  Alkali flies and brine shrimp feed on the algae.  Over a million birds flock to Mono Lake every summer to feed on the flies and shrimp, including gulls, phalaropes, grebes and others.  Waste from the birds and dead organisms sink to the bottom of the lake to decompose and act like fertilizer for the algae.  And so, the cycle is complete! 
 
Notice that there are no fish in Mono Lake.  With a pH of 10 (on a scale where 7 is neutral), the lake's waters are far too alkaline to support other life.  The water is also 2.5 times saltier than the ocean!
 
Alkali flies around a puddle on the lake shore.  They may not look appealing, but they are a critical part of this ecosystem.
Also, we noticed the flies don't bother people, so don't worry about them and leave them be.
 
Hardy as they are, brine shrimp cannot overwinter in the cold lake as adults.  Late in the season, before they die, the shrimp produce eggs designed to overwinter as "cysts."  These tough cysts sink to the bottom of the lake where they persist in a state of suspended animation until the water warms sufficiently the following spring.  These hard, leathery cysts or eggs are what is harvested and sold as "Sea Monkeys" and fish food.
 
The huge abundance of aquatic life found in Mono Lake during the summer makes the lake one of the most important sites for nesting and migrating birds in the west, particularly as other western wetland habitat has been lost to development. 
 
Two gulls, happily foraging in Mono Lake.
 
Though the ecosystem of Mono Lake thrives in a combination of harsh conditions, including desert heat, winter cold and extremely high salinity and alkalinity, it is remarkably fragile.  Because it relies so heavily on just a few species, the loss of even one species, such as the brine shrimp or the alkali fly, would be catastrophic for dependent populations - especially birds.
 
 
Abundant numbers of these tiny creatures does not necessarily guarantee a stable ecosystem, safe from collapse.  Since the entire ecosystem is essentially built on just three groups of organisms (algae, brine shrimp and alkali flies), it is very susceptible to climate change and other damaging factors.  Since brine shrimp and alkali flies are ancient, primitive creatures perfectly adapted to the saline, alkaline waters of Mono Lake, a rapid change in the lake's chemistry would likely prove too much for them to handle and result in population collapse. 

Diversion of streams from Mono Lake began in the 1940's and was finally stopped 40 years later.  Between that time, the salinity of the lake doubled (as half of the lake's volume of water was lost) and the productivity of the brine shrimp and alkali flies dropped significantly.  The loss of either one of these species would mean disaster.  In particular, the failure of the brine shrimp population one year would mean starvation for thousands of birds.
 
As you may know by now, flipping over rocks often reveals a treasure trove of unseen life.  Underneath this piece of tufa
is the remnants of dozens of alkali fly pupae.  Birds are happy to eat alkali flies during all life stages, but the pupae were
once an especially important food source for local native people.
 
If you visit:  I highly recommend stopping to check out the Mono Basin Scenic Area visitor center on highway 395 and going on a docent-led walk at the South Tufa Area along the lake.  Other activities include hiking, birding, kayaking and swimming.  (We went swimming at Navy Beach and loved it!  The water is dense, making it easy to float, but all that salt makes it important to remember to keep your mouth closed!  Also, the salt forms a crust on your skin and brine shrimp may get stuck in your hair!  Still, it's a worthwhile experience.)
 
For more information, visit: http://www.monolake.org/visit/activities

Comments

Post a Comment

You Might Also Like:

Birds of the Desert: Residents & Spring Migrants

Image
Nearly everyone knows the desert as a barren, desolate land of extremes: high heat, low precipitation; little available food and water; prickly, spiny, unfriendly plants growing in a sea of rocks and sand as far as the eye can see.  But for those who stop and look closer, the desert reveals itself as the beautiful, incredible, mesmerizing place it truly is, teeming with unexpected life. Juvenile male Costa's Hummingbird visiting chuparosa blooms next to our campsite in Anza-Borrego Desert State Park. I particularly love the desert in the spring, when the annual wildflowers, cacti, flowering trees and shrubs are all in bloom.  (I've experienced the desert in the searing 120 degree heat of summer, and the rainy, even snowy cold of winter... and spring wins every time!)  Eric and I just returned from a week in the Colorado desert, exploring the imperiled, accidental Salton Sea (more on that coming soon), the vital wetlands of the Sonny Bono Salton ...
Read more

Joshua Tree Woodlands: A Tale of Sloths, Moths and the Trees that Need Them

Image
In 1844, early California explorer John C. Fremont gave a somewhat scathing review of Joshua trees when he wrote, "...their stiff and ungraceful form makes them to the traveler the most repulsive tree in the vegetable kingdom."  Rather unkind, don't you think?  But when Joshua trees were formally described by scientist William Trelease in the 1890's, he noted that Joshua Trees are "the most attractive of all the Yuccas."  I am inclined to agree with this sentiment, and must disagree most heartily with Lieutenant Fremont! I, for one, adore Joshua Trees, with their whimsical shapes and great ecological significance!  If you struggle with plant identification, the iconic Joshua tree, hallmark of the Mojave Desert, is a good place to start.  With densely spiked tufts protruding from the ends of gangly arms stretched towards the heavens, this looks like a plant straight from a Dr. Seuss book....
Read more

A Shorebird Primer: Godwits, Curlews, Willets and Whimbrels

Image
For those of us living in the Great Central Valley, autumn is the time to head to the coast.  Of course, there is no bad time to visit California's magnificent coastline.  But as the heat and haze of summer drag on in the Valley, the sea becomes increasingly tantalizing: September and the onset of autumn bring sunny weather and an abundance of migratory seabirds and shorebirds to our coast. A new birder visiting California's Central Coast will undoubtedly be met with a splendid array of very confusing birds.  Among these are small shorebirds like  "peeps" (sandpipers), Sanderlings and various  plovers .  But the larger birds can be just as confusing, until you learn a few distinguishing features.  Four large shorebirds that are commonly seen (and commonly confused) along California's Central Coast are Godwits, Curlews, Willets and Whimbrels. Marbled Godwit (upper left), Whimbrel (upper right), Long-billed Cu...
Read more

All The Ducks!

Image
On a recent birding trip to Merced National Wildlife Refuge, I tallied up a list of sixteen different species of ducks.  Only a few more species, around twenty in total, are expected in the Central Valley of California's freshwater marshes during the winter, so I consider that to be an excellent day for ducks! North American ducks are broadly separated into two categories, largely based on their methods of foraging for food.   Dabbling ducks , also known as "puddle ducks," tend to frequent shallow water, where they are commonly seen tipping bottoms-up to feed on plant matter and invertebrates in the water and on the muddy bottom.  They are most at home in water, but walk easily on land as well, as their legs are positioned near the center of their bodies.  The wings of dabbling ducks are relatively large, which allows them to take off from the surface of the water, straight up into their air.  Dabbling ducks almost all nest on the ground, near water....
Read more

Birding in Adverse Weather Conditions: Wind and Rain

Image
Though I often extol the virtues and merits of winter in the Central Valley , especially when it comes to birding, the whole truth is that we experience "bad" weather also, just like anywhere else.  But even when the winter weather rolls in, the birds are still out there!  And sometimes, despite our best planning efforts, a birding day happens to coincide with crummy weather.   In that case, what's a birder to do?  Usually, we go birding anyway!   Birders far more intrepid than I regularly brave the ice and snow of northern winters to see their favorite birds, so perhaps you should look to them for real tips on winter birding!  For those of us in the valleys of California, the worst weather we see - wind and rain - is really comparatively mild.  Birding on an extremely windy day! I don't know of anyone who actually likes birding in the rain.  But I would argue that birding in the wind is just as aggravating as trying to bird in the rai...
Read more

Winter Gulls: The Great I.D. Challenge

Image
Gulls are a fun challenge for birders, from beginners to experts.  A few things make gulls an interesting study: they are large and conspicuous in their open habitats, so they are easy to see, easy to put a scope on, and easy to watch and study for long periods of time.  Furthermore, gulls are almost always identifiable as gulls; none of this confusing warbler/vireo/kinglet nonsense! And yet, gulls are almost impossibly difficult!  (Though perhaps not nearly as difficult as Empidonax flycatchers!) An intimidating scene to many a birder: a mixed flock of gulls.  I see five different species of gull here. Oh, and one American Coot in the background. One of the reasons they are so complicated is most gull species take two or three years to achieve adult plumage, and go through multiple molts in a year.  So, you may be looking at three or four gulls together that look like four completely different species, when they are actually just different ages (...
Read more