Monday, September 8, 2008

Blue-green algae: more than just a pest at the beach

The next time there is a beach closure due to blue-green algae, municipalities could put a positive spin on it with a sign that reads: BEACH CLOSED DUE TO LIVING FOSSIL ON DISPLAY. It won’t make up for a missed day at the beach but it will remind people that blue-green algae aren’t just a pest, they’re a part of natural history.

Blue-green algae (a misleading name as they are more closely related to bacteria than algae which is why they are also referred to as cyanobacteria) are often referred to as the ultimate ‘living fossil’. A living fossil is a species that does not look appreciably different from prehistoric fossils we find of them. Colonies of blue-green algae have been preserved in fossils called stromatolites over billions of years. In fact, some of the earliest known fossils dating back three and a half billion years look remarkably like the blue-green algae that we see today (though there is some controversy surrounding these oldest fossils as some scientist claim they were not made by biological processes but rather by physical ones). Nonetheless, the form we see blue-green algae in today is similar to the way it was when life was just getting a foothold on earth – with one important difference: the majority of blue-green algae today has the ability to produce oxygen. This is an important development for life on earth.

Three and half billion years ago, the earth was a very different place. Volcanoes were much more active, the sun was one third dimmer, and the atmosphere was mostly nitrogen and carbon dioxide. There was little to no oxygen in the atmosphere at that time. The absence of oxygen didn’t prevent life, but it did limit its complexity. At that point in history, life existed only as one celled organisms that had limited ways of producing energy. Some of them did it by harnessing chemical reactions or the natural heat of the earth and others, such as the early blue-green algae, combined the sun’s energy with hydrogen or sulphur to produce energy. Some time around 2.7 billion years ago, blue-green algae evolved the ability to perform photosynthesis, like plants do today, using carbon dioxide and giving off oxygen. Because the atmosphere was so rich in carbon dioxide and the earth was rich in other important nutrients like phosphorus, these blue-green algae were extremely successful to the point where, over the course of a half billion years, they changed the composition of the atmosphere making carbon dioxide relatively rare and oxygen abundant. This event was the first in a series that allowed the evolution of the plants and animals that we recognize today.

Their tenacity over three and a half billion years of earth’s history can be equated with their ability to find a way to survive under nearly any set of circumstances. They can be found in the harshest environments on the face of the earth including the driest part of the driest desert on earth, a place that without any rain or fog, the Atacama Desert in Chile. It manages to survive there by living off the water that salty rocks naturally draw from the humidity in the air. In this part of the Atacama, no other forms of life are supported.

Their hardiness makes them good candidates to supply food for inhabitants of space travelers of the future. The moon contains nutrients required for life but it is bound up tightly in the soil. When researchers added blue-green algae to simulated lunar soil and added light and water, they found that it was able secrete acid and unlock the nutrients from the soil. Humans staying on the moon for long periods of time would therefore not have to bring the nutrients or soil to grow their own food. Some have even speculated that under certain conditions, blue-green algae could survive on Mars.

Blue-green algae can also be used to solve problems here on earth. Currently, the efficacy of using agricultural crops such as corn for biofuels is being debated because of the large amount of energy that needs to be put into growing the crops and processing the fuel. There is potential to produce biofuels from blue-green algae. Their natural energy producing systems can be altered to produce alternative fuels such as hydrogen or ethanol directly without any processing.

While they remain pests at the beach, it is clear they are more than just pests at the beach. They transformed the atmosphere and started the ball of life really rolling. I’m not suggesting we tolerate toxic blooms. Though they are a natural phenomenon, it is human activities, such as agricultural runoff, that has exacerbated a natural problem. I’m suggesting we appreciate the bigger context in which these problems arise. We should realize that blue-green algae share more in common with us than we think. Which other two species do you know of that can change the composition of the atmosphere and has the ability to survive under such extreme conditions?

So next time you’re upset because the blue-green algae blooms have closed the beach, take a deep breath and remember where the oxygen you’re breathing in comes from.

Seen in the August 27, 2008 issue of the Brome County News

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