I absolutely love all things science, especially biology - that is why I chose my “encore career” as a science teacher. So, when I noticed the word “stromatolites” scribbled on a crumpled-up hiking map I found in a local bar, I was charged up. A plan for an afternoon hike along the east beaches of Stocking Island, Bahamas in search of stromatolites was born.
We landed our dinghy on the lee (calm) side of the island and climbed over the dunes to the windward (windy) side where we found a gorgeous three-mile long sandy beach. We had to “share” the beach with maybe ten other visitors, a “crowd” by our new southern Bahamas standards. Walking along the beach for about a mile at low-tide, we reached the stromatolite formations and I got totally jazzed.
Hidden in Plain Sight
To be perfectly honest, you’d have to know that the stromatolites were there or you’d walk right by them. The formations basically look like large, brown, flat, rocks interspersed in the sandy beach. But, I knew that they were beautiful living examples of the very earliest forms of life to have ever existed on our planet- perhaps 3.5-4 billion years ago, and were an essential ingredient to almost every other form of life which has ever lived here. I was in heaven!
Mini-science Lesson - What Exactly are Stromatolites?
What’s up with these stromatolite thingies? Almost all available evidence indicates that the earth was formed about 4.5 billion years ago. But, the earth was very different then, with lots of volcanoes and huge oceans. The atmosphere contained large amounts of carbon dioxide and very low concentrations of oxygen, certainly not very conducive to life as we know it today.
About 3.8 billion years ago the fossil record begins to reflect the presence of stromatolites built by single cell “bacteria like” critters including Cyanobacteria. Cyanobacteria are weird little guys with a few capabilities which are important for this discussion. They perform the process of photosynthesis (ie -using light to make their own food, produce oxygen, and consuming carbon dioxide and water in the process). They can move towards light and form a “bio-film” which is basically a huge convention of Cyanobacteria organized into a sticky, slimy mat.
A stromatolite is formed when sediments in the environment stick to that biofilm forming layers of sedimentary rock interspersed with living Cyanobacteria, in essence “living” rocks, which continue to grow microscopic layer by layer. They produce enormous quantities of oxygen, and probably were a primary source of the additional oxygen which made more complex life forms possible on early earth.
Modern Stromatolites are found in very salty lagoons in various places around the world, but there are only 2 places where they can be observed in the marine environment, Western Australia, and right here in our backyard in the Exumas! These formations have been studied extensively by various researchers from the University of Miami and you can see the growth measurement stakes in the background of some of our pictures.
So there ya go! While most people are seeing brown, flat rocks, I’m dreaming about 3.5 billion years of evolution and standing by the living rocks that made it possible. How cool is that!!!