Euglena : Ecosystem Engineers

In 1995 an extremophile, or organism that thrives in extreme environments, was discovered in the United States in a lake outside of Butte, Montana. The body of water where it lives, known as the Berkeley Pit, is a former open-pit copper mine that is slowly filling with groundwater that dissolves heavy metals like arsenic, cadmium, zinc, and aluminum from the mine’s 2,000-foot-deep surface; the dissolved metals mix with the water to form a toxic (poisonous) solution. The Berkeley Pit is the largest hazardous waste site targeted for cleanup in the United States. As 2.6 million gallons of groundwater seep into the pit every day, the toxic brew edges ever closer to spilling into the Clark Fork River, which makes its way to the Columbia River and out to the ocean, representing a massive-scale ecological threat to the fisheries and communities in these areas.

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Though the water in the pit is as acidic as lemon juice and considered inhospitable to life, a novel species has emerged and is slowly but surely changing the lake’s toxic brew to one more habitable. An analytic chemist studying the lake noticed a clump of green slime floating in the lake and brought a sample to Dr. Grant Mitman of Montana Tech. Mitman brought his colleagues Don and Andrea Stierle into the lab, and they identified the slime as a colony of Euglena mutabilis , a single-celled organism that forms algae-like mats. How Euglena came to grow in the Berkeley Pit is unknown, although some attribute its spread to a flock of 350 snow geese that landed (and subsequently died) in the lake several months prior to the discovery of the organism. The geese may have carried reproductive material of the Euglena in their feces (waste matter).

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Euglena are among the oldest organisms in the world, having survived since the time when conditions on Earth were not too dissimilar to those found in the Berkeley Pit- -ancient acidic oceans were full of heavy metals and other free- floating elements. These unique creatures exhibit traits of both plants and animals: they can photosynthesize (produce their own food using sunlight), but they can also move around in search of food. Their ability to photosynthesize produces oxygen. As a result of this oxygen combining with the dissolved iron in the water and by other means, the organisms cause iron to separate from the watery solution in the form of a solid, thereby creating stable substrates (surfaces) for other organisms to inhabit. In other words, Euglena are ecosystem engineers. They work to improve the environment for themselves and, in doing so, make their surroundings more habitable for other organisms. This type of bioengineering (engineering using biological organisms) fostered the development of all life on Earth, since the production of oxygen led to the proliferation of organisms that depend on oxygen, . and over the course of billions of years, the stable iron-based substrates eventually contributed to the formation of landmasses out of what was once a planet covered by water. Species like Euglena manufactured the current configuration of air, water, and land that makes this planet so uniquely hospitable to life today.

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In the Berkeley Pit, Euglena are doing similar work. They thrive in the heavy-metal laden waters of the lake and are removing the iron, zinc, and cadmium out of solution, storing it in their bodies, and rendering the metals biologically inactive. When they die, their bodies and the metals’ they contain are deposited in the sediments at the bottom of the lake. The chemistry of the Berkeley Pit is changing slowly but surely, and research is underway to encourage the population increase of Euglena and similar organisms to biologically treat the water before it spills into critical waterways. Since the discovery of Euglena , more than forty species of similar microorganisms have been discovered in the lake, several of them new to science. Many of these have found suitable habitat because of the pioneering work of Euglena , and they also serve to neutralize and repair the pit’s toxic water. Species like Euglena are fascinating from an evolutionary perspective because they exhibit traits that not only confer advantages to their own species, but also create conditions that enable other types of life to thrive.

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