Thursday, August 18, 2011

Shark Bay Squee!! (part 3: I Commune with Ancient Life)

Now, ladies and gentleman, here is the post that may convince you I'm a little cracked (if you hadn't come to that conclusion already). So, here goes: My name is M and stromatolites make me swoon.

What the hell are stromato-whatsits?
Stromatolites are "living rocks", sedimentary limestone built by a thin layer of cyanobacteria on the surface of the structure. This is how it works: a thin layer of blue-green algae (like the slime that floats on top of ponds) traps teeny tiny particles of sediment (like a grain of dirt floating in the water) in their mucus membrane. The cyanobacteria cements this sediment to the rest of the rock, and thus slowly adds layer upon layer. Microscopic single-celled organisms creating structures thousands of times larger than any one of them, structures that last for millions of years? Good luck beating that, architects of the world.

Let me repeat that: bacteria that build rocks.

You're a huge rock-dork. Why should I care?
There is a huge abundance of stromatolite fossils in Precambrian rocks, ie, rocks formed before the Cambrian explosion, when life on earth really took off, about 530 million years ago. Stromatolite fossils (with evidence of microbes/cyanobacteria/life present in the fossil) have dated to at least 2.7 billion years ago, and probably as far back as 3.4 BILLION years ago. For a quick reference to just how ridiculously old that is, mammals have only been on earth for about a tenth of that time.

This means that stromatolite fossils are some of the earliest confirmed evidence of life on earth.

Okay, they're old. So what?
Cyanobacteria photosynthesize; like all plants, they "breath in" carbon dioxide and "breath out" or produce oxygen (even if you think geology is pretty boring, you have to admit that oxygen-producers are in your interests). Oxygen-producers like the cyanobacteria on stromatolites are what created the atmosphere as we know it today, ie, filled the air with oxygen. You and I would not be here, breathing the air we are breathing, without stromatolites slowly, steadily inhaling and exhaling into the barren earth, millions of years ago.

Let me repeat that: bacteria built the atmosphere.

...... Alright, I might be just a little interested now. Why is this on your blog though?
*drumroll* I got to go see one of the very few marine stromatolite colonies on the planet, at Hamelin Pool, in Shark Bay (about 10 hours north of Perth) . These stromatolites are about a few hundred years old, and they have survived this long because Shark Bay has just the right conditions. Stromatolites are pretty delicate creations (for all that they survive in the rock record); they need the right sort of environment, similar to early earth, ie, shallow, salty, and fairly warm. The Faure Sill, a bank of sea grass that sits at the mouth of the bay, keeps the bay much saltier than the surrounding ocean. This saltier water limits the kinds of fish and other marine organisms that can survive in the bay, which protects the stromatolites from overgrazing by little fishes that like to eat algae.

So, without further ado, some pictures!!

Hamelin Pool in the afternoon sun.

These (slightly annoyingly silly) signs helped inform visitors.

These are dead stromatolites called Red Caps; they died when sea level fell, and no one knows why they're red.

Living stromatolites!! Squee!

Stromatolites come in different shapes, but the iconic "club" shape is what you see in the picture above.

Fishies! It was very cool to watch them swim in and out of the stromatolite mazes.


This was my favorite spot. <3

I like it because this stromatolite has a hole in it AND looks like a snake.

The curve of the coast of Hamelin Pool, protecting the Stromatolites.

M likes stromatolites.

Sunset over Hamelin Pool.

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