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One microbialite, Two microbialites, Bulbous microbialite, Pointy microbialite

Posted on March 25th, 2009 by Margarita Marinova

Welcome to the Pavilion Lake microbialite garden! To the right you will find the cauliflowers, straight ahead are the cauliflowers with chimneys, to the left we see the artichokes, and off in the deep end you can find some corals!

Cauliflowers with chimney structures

Cauliflowers with chimney structures

We didn’t plant the microbialite garden, but the Pavilion Lake Research Project team is there to study it. Microbialites are carbonate structures that form in water with the help of microorganisms. Commonly we see carbonates as limestone, but in certain special cases – often when life is involved – the carbonate precipitates to form some very unique structures. These microbialites are interesting because they can help us understand the types of structures that microorganisms form and the biological signatures they leave behind. We can then use this information to study similar structures from over 2.5 billion years ago. Microbialites are present in a number of lakes around the world, but what makes Pavilion Lake so special is the remarkable diversity! Not only is the lake full of microbialites, but the structures range in size, morphology (shape), and depth!

Artichoke structure

Artichoke structure

This is where our garden analogy comes in. As we explored the lake, we saw that the great diversity of microbialites fell into four general morphological categories: cauliflower, chimney, artichoke, and coral. From the four locations around the lake that we had decided to study intensely at the start of the project, these morphology types seemed to correlate with depth. We found the bulbous structures in the shallows, with chimneys, artichokes, and coral-like structures at increasing depths.

The microbialite structures are complex, and truly require a team with diverse skills and interests to study them. For me, the influence of physical factors on where and how the microbialites grow is incredibly interesting! Some specific questions that we are asking are: does the type of observed structure correlate with amount of light at that location? Is the mineral composition of the microbialites different between structures? Does the depth or the type of material on the lake bottom determine what type of microbialite grows? Studying the effects of light and temperature tell us whether biology is involved, as photosynthesis and therefore rate of growth depend on these parameters. Conversely, a relationship between mineralogy and morphology could mean a more abiological and chemical control on the shapes of the microbialites. One way of answering these questions is by placing sensors on the lake bottom – near microbialite structures – and recording the environmental conditions that the microbialites feel throughout the year. To assess environmental conditions we must collect years of data to be confident in the trends: for example, just because one year is cloudy and cold doesn’t mean this is always the case!

Cauliflower structures

Cauliflower structures

Another important approach that was started last year has been the use of the Deepworker submersibles. With these submarines we have been able to take high definition video of everything that the pilot sees: truly exploring the lake bottom without the constraints of scuba diving. We have used the video collected by the subs to map the lake bottom, that meant looking at more than 70,000 images, but it was well worth it! The mapping allowed us to really understand the distribution of microbialites over the entire lake and be able to more confidently say if morphology type correlates with factors like depth or lake bottom material. We certainly were in for some surprises when it came to the distribution of morphologies! For example we found that artichoke structures are distributed over a much larger range of depths than we had previously thought, and this coming summer we will be testing the hypothesis that the microbialites need a hard surface, like a rock, to start growing.

Coral-like structures in the deep end

Coral-like structures in the deep end

There is a lot more work to be done in understanding these microbialite structures. Pavilion Lake keeps us coming back with its fascinating science questions and enchanting structures: the depths of the lake are a window to the past, yet rooted in the present. Year after year we use these structures as a key to understanding the oldest life, the smallest organisms, and the most wondrous lake in beautiful British Columbia. What’s not to love?

:-) Mars

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