18 October 2015 – Microbial pilgrimage

There are a handful of places around the world that are really special to evolutionary biologists.  Think of the Galapagos and Down House in Kent, for their connections to Darwin, Linnaeus’ gardens in Uppsala, Sweden, or Mendel’s pea-laden ones in Brno, Czech Republic, the Burgess Shale on the Alberta/BC border for its weird fossils of the Cambrian faunal explosion, and Hadar, Ethiopia, where the bones of Lucy, the famous australopithecine, were discovered.  And then there are other, even nerdier scientific pilgrimages, like the one Luis, Fiona, Jesse and I made on a fine October day to go see… mats of mostly dead microbes.

We packed up our diving gear and drove some 350 km to Pavilion Lake between Lillooet and Cache Creek, northeast of Vancouver.  The long, skinny lake is squeezed between highway 99 and the steep wall of Marble Canyon.  If we could have ignored the Ponderosa pines, Douglas firs and juniper bushes on the dry limestone slopes, we could have easily imagined ourselves transported to much warmer climes.  The shallow parts of the lake were as beautifully turquoise as the Caribbean Sea.  We donned our dive gear and walked in.  The Caribbean illusion continued.  The water was so clear that it was like diving in vodka, and then we saw the objects of our quest: stromatolites.

Strom 1

Stromatolites look like rocks, but like coral reefs, they are built by living organisms.  In the case of stromatolites, the little builders are plant-like bacteria that trap and cement together grains of sand.  Bacteria die; new ones grow on top of the dead ones and continue the process onwards and upwards, forming flattened soufflé-shaped mounds after many, many generations. The oldest ones in Shark Bay, western Australia, are about 3.5 billion years old!!  Yes, that’s billion with a B. That’s close to the very beginning of life on Earth, when oxygen levels were just starting to rise above the primordial soup – perhaps kick-started by the photosynthetic microbes that built the mounds.  The stromatolites of Pavilion Lake are much younger than that; they started to form around 11,000 years ago when glaciers retreated.

Strom 2Stromatolites were everywhere we looked.  Small ones, just 20 to 30 cm high, carpeted the shallows, and much larger ones, reminiscent of Gaudi’s Sagrada Familia, stood deeper in the lake.  The structures, so superficially similar to coral reefs, were strangely deserted. While coral reefs swarm with life – especially fishes – stromatolites were devoid of colour and movement.  We found just three small sponges and two shrimp hiding among them.  Nevertheless, the grandiose architecture of these structures and the enveloping underwater silence, punctuated only by our breathing, made for an experience as mystical as any I can imagine.Pavilion dive

Running low on air and feeling chilly in the 11oC water, we reluctantly ended the dive.  After a quick mid-afternoon lunch, we headed back to the city.  700 km of driving for one hour of diving.  It was as crazy as it seems, but what an hour it was!

 

Pavilion group

 

 

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