Hot Spring Fed Basin Lake Biology Essay

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Mono Lake is extreme for a lot of reasons; physically, Mono Lake is extreme because it is between one and three million years old, one of the oldest lakes on this continent. A creek and hot spring-fed basin lake on the eastern slopes of the Sierra Nevada, it's home to two islands, Paoha Island, and Negit. Both are volcanic in origin and are part of a line of craters; the whole shebang remains an area wrought with earthquakes. This lake has quite the dark side too, with an extremely high alkalinity (pH 10), and a salinity almost three times that of sea water, Mono Lake claims everything it touches by 'licking' it with calcium deposits. If an object is submerged, this deposit becomes a calcium carbonite scale. Plants killed by the lake take on a ghoulish white appearance, fossilizing in a coating of lime.

Mono Lake is a chemically extreme aquatic and terrestrial place to call home, so extreme (you may get tired of the term) that very few organisms, so-called extremophiles, are the only sort that can survive in such harsh hypersaline conditions. Instead of using photosynthesis, some bacteria in Mono Lake use arsenic laden chemicals to produce their food. Even sea creatures couldn't survive this salty mess; it's completely inhospitable for fish, but a great place to raise a couple of thousand Alkali Flies and Brine Shrimp. The flies eat the chemoautotrophic bacteria and algae, then supplying flocks of California Gulls, American Avocets, and Eared Grebes. The shrimp and flies are the only animals that can survive these harsh waters, making this one of the most simple, undiversified and fragile ecosystems found on Earth. The bonus of having an undiversified population is in number, and both the cases of Brine Shrimp and Alkali Flies, populations can be huge as long as conditions permit. And if they don't? The Brine Shrimp have it covered. They produce eggs with thicker shells when the water quality, pH and salinity isn't up to grade, making it possible for all of us to have our own "Sea Monkeys" right at home (or wherever the eggs are carried on the feet of migratory birds). Alkali Flies are tiny machines of Mono Lake efficiency. Feeding on algae, cyanobacteria and diatoms, these flies can actually extract the bicarbonate ions from their blood (the same which make the lake alkaline), mix them up with calcium, and then in lime glands, deposit them as calcium carbonate. Say there's not enough oxygen in the lake, even in the deepest parts: no biggie, the larvae just whip out a breathing tube similar to those used by mosquitos and directly penetrate the surface with an evolutionary crazy straw.

Another regular to this scene is the Eared Grebe, coming to feast on both the shrimp and flies. What makes these birds so interesting and fitting to this extreme environment is the adaptability of their garb and a unique whale-like tongue made-to-order for eating those plankton-like Brine Shrimp. Eared Grebes use their own darkly-hued solar radiant skin, fluffing back their feathers to warm themselves on colder days; while in the summer, they take a sleek plumage, with little white feathers exposing the skin. If only humans were so adaptable. Another interesting inhabitant is the American Avocet with its upturned bill perfectly designed to root the bottom of ponds and saline lakes. What's particularly darling about these Avocets is a ritualistic behavior of tandem feeding leading to mating in pairs. It sounds like "Date Night: Mono Lake" to me. An interesting addition to the crew at Mono is the non-adaptive, but salt-tolerant Gadwell duck that come to feast on the Alkali flies, leaving the Brine shrimp completely alone. Though these ducks eventually acclimatize to the hypersaline water, necrosis of the feet begins to form which can severely impact them when food is scarce or when the condition becomes disabling in adults (Jehl). What remains a mystery is why these Gadwells and other waterfowl, harmed by this extreme and for them, temporary habitat, are protected under management plans for Mono Lake in place of organisms that actually depend on this hypersaline environment (Jehl).

From one extreme to another, from salty to ice: Antarctica is surrounded by the southern parts of the Atlantic, the Indian, and the Pacific Oceans. A belt of sea ice between 500-1,500 km wide and 3 meters thick forms outward from the continent in winter, contracting in seasonal cycles (though even in summer this belt is 150-800 km thick in most places). Seasonally, the area of this sea ice varies from 3 million square km (summer) to 20 million square km (late winter) making these seas a thermally extreme aquatic habitat all year round. Even with all this ice, Antarctica is a polar desert, receiving about 2 inches precipitation annually. Life is so hard on Antarctica the few plants that do survive can't support vertebrate life, however, when one looks to the sea, a wealth of life can be found. This life is represented in a simple food chain when compared to swankier (more diversified) locales. The amount of diatoms present is similar to that of grasses in land-based ecosystems and can only support as many lunchers as the environment allows. The primary producers are diatoms (including plankton) which are munched by krill (the primary consumer), who's then eaten by crabeater seals (predatory secondary), who's finished off by the top predator, the killer whale (tertiary consumer).

One interesting inhabitant of the polar seas: Artic Krill have specially adapted to their environments by being able to withstand long periods of time without food, much longer than Krill from warmer climates (Johnston & Clarke). Eating up those Artic Krill are the Crabeater Seals, amazingly prolific, with estimates numbering about 30 million in the Antarctic. These seals do not eat crabs, but they have specially evolved teeth designed for filtering their snack of choice, krill. A fabulous example of extreme artic adaption is the Bald Rockcod, swimming along the bottom and surfaces of sea ice and reaching lengths of 28 centimeters. The Bald Rockcod's color changes depending on whether it feeds along the bottom (dark olive fish) or near the surface (silver white fish). They love to snack on ice krill, and are enjoyed by penguins and seals. One of the interesting things about this fish is the silvery camouflage it's evolved to mask it's dark organs and iris. This fish is so perfectly adapted to its environment with the development of antifreeze glycoproteins, cold-stable microtubules, structural modification of enzymes, and cardiovascular adaptations; it's also allowed adaptions that would kill it in any other location. Having glycoprotein antifreeze in your body fluid inhibits the growth of ice crystals, but these fish have no hemoglobin in their blood! Because cold water holds more oxygen than warm, these fish adapted to what would be a horrible mistake in any other location. These fish, like other Artic adapted marine organisms are in most cases, slower to hatch and develop, with larger eggs or larvae. Most evidence suggests the resting metabolic rate of these polar adjusted fish to be twice that of more temperate fish in cold waters. Artic fish tend to have slower muscles and use more muscle mitochondria than temperate counterparts, moreover, these fish are built for short bursts of speed, escaping predators, though temperate fish are better designed for higher power outputs, higher tail-beat amplitudes, and fast moving juveniles (Johnston & Clarke).

Vernal Pools are temporary aquatic habitats with no present predatory fish destined to dry out every season and replenish with the rains. These pools are literal examples of both resource partitioning and the delicacy in which ecosystems interact (Kneitel & Lessin). These islands of life midst seas of grass are surprisingly complex, though sometimes only moderately genetically differentiated (Calloway; Ramp et al). There are vernal pools worldwide, but in Central California, they make a unique and significantly at-risk habitat, key in preserving our native flora and fauna. Life is fast paced, but exceedingly rich in these pools, as California's wet season usually runs from November/December to Mid-April (Marty; Kneitel & Lessin). No nutrients are wasted; algaes, phytoplankton and plants grow in each layer in the pools feeding the Daphnia and tadpoles. They in turn feed a bevy of bugs which feed the larger, longer-developing creatures like the endangered Tiger Salamander. Vernal Pools are temporary oases of life. Where creatures in extreme aquatic habitats, chemical or polar, have physically evolved and adapted to the harshness of their surroundings, dwellers of Vernal Pools have adapted to a short, seasonal life, migration to larger, permanent ponds and/or keep-it-in-the-family methods of breeding to ensure species survival (Holland & Jain; Ramp et al). This tactic of self-compatibility creates very specific regional species, but also very fragile systems and with human interference by land development, water pollution and the introduction of invasive/exotic species, Vernal Pools need protection now more than ever.

The Tiger Salamander is a creature, much like the Bald Rockcod and the Alkali Fly, perfectly adapted to its environment, but what if that environment was reduced to only 3-10% of its original size (Kneitel & Lessin)? All of those special adaptions (think of the loss of hemoglobin in the Rockcod) are now evolutionary mistakes and in the case of this Salamander, loss of habitat is all but damning. In the last three generations, California Tiger Salamanders have lost an estimated 30% of their population. These salamanders grow slowly, the larva eating aquatic insects, crustaceans and tadpoles for two months, at points becoming cannibalistic to gain the body mass needed to become an adult through metamorphosis. With the rainy season being barely three months, only the largest, longest lasting pools can maintain these California Tiger Salamanders. Adults, who look like large mouths with a tail, must live in burrows of moist soil, waiting for the first rain to summon them back to the edge of the pool for mating. The fellas come out first, waiting for nightfall and a slimy honey to nudge about until she reciprocates, at which point he bestows his spermatophore, which, if she doesn't have a headache, is taken into her cloaca. After a day or two, she'll string her eggs along the grasses on the bottom of the Vernal Pool and everyone with go home. It takes two months for those babies to hatch, and another three to five for the larva to metamorphose. Those that can make it against all those odds can live up to 25 years.

Resource partitioning is a huge part of the success of a habitat regardless of the harshness of conditions. Even in a tropical paradise, if there is too much competition for food, starvation occurs. The conclusion from studying these three harsh environments is simple: they function because the plants and animals do not have to compete for resources. Everything has its place, every species has its niche; those that overlap will find one an evolutionary victor while the other fades away. In such extreme environments, we can clearly see such evolutionary winners like the Bald Rockcod, Alkali Flies, and the Tiger Salamander, who's evolutionarily winning so hard at its habitat the loss of Vernal Pools is literally killing them. These organisms have not only succeeded in some of Earth's harshest environments be they by chemical, thermal or by length of time itself; it is there they thrived.

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