Hamelin Pool (Shark Bay) Stromatolites - November 2016

[digit]

Well, on this trip we didn't actually hunt for anything (the signs and route were pretty apparent and no collecting was allowed), there were technically no fossils (though stromatolites predate most other life forms and have been inhabiting the planet for some 3.7 billion years), but you can't deny it was a trip so, though only scoring one out of three, I'm posting this in the Fossil Hunting Trips section. It was quite a trip and one I've had on my bucket list for some years now. I've visited (even dived, surveyed and sampled) the living stromatolites in Lee Stocking Island in the Bahamas and wanted to pay my respects to the other (more) famous modern-day locality in Shark Bay, Western Australia.

 

Some may not know of the larger (up to 2.5 meter) Bahamian variety of stromatolites. These exist not due to hyper-saline conditions (barring other competing life forms) but due to the crazy currents that run through the channels which shift huge amounts of oolitic sands which frequently bury these stromatolites for extended periods of time. The cyanobacterial mats are not only tolerant of this periodic smothering but actually make use of the sand grains in constructing and cementing their layered structures. Other benthic organisms like corals, macroalgae and other invertebrates can't tolerate being buried from time to time and so the stromatolites capitalize on these special circumstances that allow them to proliferate unchallenged. Here are a few quick web links for those who've not heard of the Bahamian forms:

 

http://www.bahamas.com/vendor/stromatolites-exumas

https://appliedecology.cals.ncsu.edu/absci/wp-content/uploads/18_Stromatolites-Brochure.pdf

http://www.robertriding.com/pdf/riding_etal1991-bahamas.pdf

http://fire.biol.wwu.edu/trent/alles/Stromatolites.pdf

 

We had planned the drive up to Shark Bay from Perth as the final leg of our Australian anniversary trip. With some good insight provided by TFF member Dave (@sandgroper) we plotted a course for several days sightseeing along the western coast of Australia to terminate at its northern extent at Shark Bay with the primary goal of paying homage to the life form that terra-formed this planet nearly 2.3 billion years ago by reducing the percentage of atmospheric carbon dioxide (pumped out by all those volcanoes early in earth's story) and increasing the level of oxygen from its initial trace amounts--called the Great Oxygenation Event (GOE) or the Great Oxidation. At first the oxygen released due to the photosynthetic activities of the cyanobacteria apparently was quickly absorbed by huge amounts of elemental iron in the earth's surface and oceans. I've heard that the earth's oceans would have had a green tinge till all of the dissolved iron precipitated out as rusty iron oxide (the source of many of those iron ore deposits today). Once the iron was done consuming all of the oxygen being produced by the cyanobacteria, the atmospheric percentage was finally allowed to climb to today's levels (actually, even higher in the past). This oxygen was one of the factors in allowing multi-cellular life (and eventually even fossil-hunting Homo sapiens) to evolve. It is for this reason that I felt the pilgrimage was in order--a creation story combined with a sort of cautionary tale of a species that so changed the world that it could no longer survive as the dominant species. Sound vaguely familiar?

 

Anyway, enough exposition--onto some photos from the trip. We had started that morning further down the coast at Kalbarri and had left just after breakfast to make the three hour drive north to Hamelin Pool. While there was not really a great change in latitude during those three hours of listening to podcasts while enjoying the changing scenery, the temperature difference was amazing. When we left Kalbarri it was around 16C (61F) and was probably headed to a high of around 26C (79F). We could feel the outback-like temps when we made a stop at the Billabong Roadhouse for a quick break and refuel. By the time we were in the parking lot at the Hamelin Pool Marine Reserve interpretive boardwalk the thermometer in the car was reading an incredible 40C (104F). We lathered on some SPF100 sunscreen, donned our field hats with the long cape in the back, took a long drink of cool water and ambled (slowly) toward the boardwalk. The boardwalk is well illustrated with nice signs providing some good basic information on this special ecosystem for those tourists unfamiliar with these special microbial communities.

 

  

 

  

 

 

As we seemed to be visiting Australia outside of the normal tourist season, we had the entire place to ourselves (as we'd experienced in many other places we visited on this trip). The site has a well constructed boardwalk built over the shore and out to a great vantage point to see the stromatolites in all their glory. Truth be told, they are not really impressive structures (probably mostly less than half a meter and mostly a blackish or brownish in color except for those furthest from shore which are exposed to the air for the least amount of time during low tides and were more sand colored). I can understand that most tourists making this stop might not appreciate the uniqueness of this site and I can picture most families would likely stop for a quick selfie while the teenage kids barely look up from their devices to glance at the odd arrangements of mushroom-like blobs arrayed before them. I can say that for Tammy and me it was an odd surreal experience to stand at this spot that I've seen in so many online photos and realize we were actually there--not unlike the powerful feeling of standing in front of a half-buried moai on Easter Island and staring into its unseeing face.

 

Of course, being spring in this part of Australia the flies were fierce. They took special pleasure in investigating every possible inconvenient (and irritating) spot on your head to crawl around and covered us in swarms seemingly immune to any waiving of arms (and it was just too hot to even attempt that). We happily made use of our best purchase during this vacation--an inexpensive A$6 fly net to wear over our hats. It wouldn't keep them from covering us like barnacles on a whale but it did keep them from our ears, eyes, noses and mouths and that was enough to make them tolerable.

 

     

 

 

We got there (by chance) at just around dead-low tide and were able to easily see the field of stromatolites stretched out before us. At the edge of the stromatolites were a small group of Pied Cormorants (Phalacrocorax various) preening themselves and resting in the hot morning sun. I hadn't expected to see fish swimming in the hypersaline waters but some small silvery species (no idea which) seemed to be tolerating the conditions well and thriving.

 

  

 

  

 

 

[digit]

Some of the interpretive signs explained how changes in depth along the profile of the beach resulted in various forms of microbial growths from microbial mats to microbialites to fully-layered stromatolites. Here you can see some images of each of these types of structures from the thin microbial mats at the top end of the beach near the high-tide line, to the zone of flatter but more structured microbialite forms to the lumpy (black cauliflower-like) pedestalled layered stromatolites.

 

     

 

  

 

 

     

 

 

[digit]

To give a better feel what the expanse of this array of stromatolites looks like when you are standing at the end of the boardwalk, here are a couple of panoramic composites giving a pretty good feel for view from this vantage.

 

 

[digit]

After spending a day exploring Shark Bay and seeing dugongs (an estimated 10% of the world's population of dugongs lives in Shark Bay) and also encountering Emus in the wild (a real sight to see) we retraced our steps and on our way back south stopped in again to revisit the stromatolites one last time. The temperature had moderated quite nicely and it was much more comfortable than the previous day. We also caught the stromatolites at high tide. I'd been hoping to do this to see how they appeared when submerged. The effect was interesting but they were not as easy to see as when we had fortuitously caught them at low tide the previous day.

 

 

 

 

  

 

I'm really glad that Tammy and I were finally able to visit this iconic location (at least to those interested in geology or paleontology). I would highly encourage any TFF members living in (or visiting) Australia to make the effort to visit this site and take in the rarity of this ecosystem and its unusual life forms. Take a deep breath of clean air while there and thank them for all the oxygen.

 

 

Cheers.

 

-Ken

 

[Raggedy Man]

Thanks for taking us a long Ken! 

[digit]

One of the best parts about surfing the articles on TFF--no passport needed.

 

Cheers.

 

-Ken

[jpc]

Excellent report about a place that is also on my bucket list.  Thanks. I like the high and low tide aspect.  

[digit]

I wanted to visit it at high tide as well to see how different it looked. I considered getting up at dawn and making the hour plus drive back down the peninsula (from Denham) to see it in the morning but we were scheduled for a boat ride that morning to try to spot dugongs (and not the fossil ones from Florida). I lucked out that by the time I got back down to this area that the tide was near high. Interesting to see it both ways but definitely best to try to arrange to see it at low tide if you only get one chance.

 

Cheers.

 

-Ken

[abyssunder]

I could sit there in a glance of wonder...
Thanks for sharing, Ken.

[digit]

12 minutes ago, abyssunder said:

I could sit there in a glance of wonder...

 

Just the effect I was going for. Felt the same way seeing it in person.

 

 

Cheers.

 

-Ken

[Ridgehiker]

Thanks for being our our guide.  Felt like I was there. Really neat locale. 

 

The more we lean about a a particular form of life, he more fascinating Naure is. 

[doushantuo]

Terrific report,awesome photography.

Kudo's to digit for this piece of journalism!!!!

Me like.

[MikaelS]

There is a huge variety of stromatolites in the Shark Bay area. Some are quite large and many are more impressive than those visible from the board walk. A recent paper by Phil Playford (the geology of Shark Bay) includes numerous colour photographs (including under water images) of all stromatolite forms in the area. Many of the stromatolites closest to the shore are 'dead' as there has been a one metre relative sea level fall during the Holocene.

[ynot]

Thanks for another fantastic report Ken.

Tony

[sandgroper]

Glad you enjoyed seeing them Ken. The flies are bad, worse than normal for this time of year because we have had a particularly wet winter, even around Shark Bay. The other problem is the easterly winds, if its blowing an easterly they are terrible because they are blown from the desert country to the east right out to the coast.  I like seeing the stromatolites in high tide, particularly on the still days with no wind. You certainly didn't get the best of conditions to travel this part of W.A. with the wettest, coldest winter for many years but I'm really glad that you enjoyed it and I'm pleased I could offer some help.

 

 

[Doctor Mud]

 

Thanks Ken,

 

Definitely on my bucket list!

 

 

I remembered seeing on the documentary series "Coast" that these lines are tracks from horse and Camel (??!!) drawn wagons used many years ago to load wool and sandalwood onto barges to be taken out to ships. Evidence for the extremely low growth rate of the stromatolites. Some will be hundreds of years old.

[sandgroper]

Yep, thats right. The camels would walk out until the water touched their bellies, then the wool was transferred onto small boats to be taken out to larger boats. The tracks of the carts are clearly visable, amazing after so much time.

[digit]

8 hours ago, MikaelS said:

Many of the stromatolites closest to the shore are 'dead' as there has been a one metre relative sea level fall during the Holocene.

 

I noticed the nearshore stromatolites were black and those further from shore (and mostly underwater even during low tide were more sand colored. The live stromatolites in the Bahamas are virtually the color of the surrounding sand. I wondered if the closer ones that had turned black were not getting enough hours of submersion and had dried out and changed color. Your comments seem to confirm my suspicions. Stromatolites of a more healthy color can just be seen at the furthest extent off shore in some of my photos as well as the nascent forming colonies in the large (non-black) opening on my second panoramic above.

 

In June, 2006 I was part of a team that did surveys and took samples (both deep core samples and harvesting a small stromatolite for sectioning and detailed study of the growth pattern). This trip was organized as an Explorers Club mission and we carries flag #53 on this mission. The stromatolites in the Adderly Channel, Exumas Cays, Bahamas look significantly different from those in Shark Bay. They are in deeper water and so can grow to much taller sizes. They also tend to have characteristic "petaled" sides that make them slightly resemble a large rose (or artichoke). We suspect this is due to the strong currents that sweep through the area. As they grow in normal sea water (not hyper-saline) other organisms can share the space with them. You'll see in the photos below that occasionally macroalgae has a chance to get a foothold on the stromatolites. This doesn't tend to last too long as currents occasionally bury them with oolitic sand for long enough periods to keep the overgrowths from dominating.

 

  

 

  

 

     

 

 

We released dye and filmed the flow around the stromatolites to try and determine if the petaled textures of the sides had anything to due with the currents that race through the Adderly Channel four times a day. We tried to finish our dives before the currents were ripping at their maximum but I remember having quite a few wild rides crawling along the bottom back to the anchor line and flapping in the "breeze" on the ascent to the ship.

 

You can also see in some of the close-up photos the fuzzy texture of the cyanobacterial mats at the surface of the growing stromatolites. Many samples were taken and preserved for later viewing through microscopes.

 

     

 

 

 

 

 

[digit]

We also had a team with hydraulic power tools that were driven by a 16 hp engine on a Carolina Skiff positioned above the working team. We drilled down through the substrate and took long core samples to get an idea of the longer term history of this channel.

 

  

 

We also had a large metal tube and an air hose running compressed air down to one end of it. A valve would turn on the air and the buoyancy of the air rising through the tube would create a suction which was used to pull up and eject the sand about 20 feet away (it was a long and unwieldy tube). You didn't want to get your hands too near the suction end when it was running. More than once operators had their gloves sucked off their hands and ejected far away. We used metal panels to keep the oolitic sand from sliding back into the pit we were excavating. Oolitic sand forms from the direct precipitation of calcium carbonate around a tiny speck of a nucleus. As a result, the sand grains are spherical (like tiny styrofoam bead) rather than angular like normal 'sharp' sand that is usually the result of herbivores (parrotfishes and to a lesser extent surgeonfishes) scraping reefs to feed on the turf algae. I like to tell people the white sand beaches that tourists are fond of are comprised primarily of parrotfish poop. Anyway, this spherical sand does not pack as well as the interlocking sharp sand and you can quite easily plunge your hand up to the wrist into the bottom as the sand beads part with ease. This also means that any hole you dig fills back in as the sand is almost liquid in nature--hence the metal panels to allow us to get to the base of a stromatolite.

 

  

 

 

 

Once we had a base cleared we used large hydraulic drills to weaken the base of attachment of the small stromatolite we had chosen to harvest for later studies. The hydraulic oil we used to run the heavy machinery is actually plain vegetable oil with a yellow-green dye in it which helps locate any leaks in the hoses or connections. Toward the end of drilling a small leak kept growing despite layers of duct tape and other measures to try to stem the hemorrhage. Our primary drill operator at the end (they took turns as it was exhausting) was a guy with white hair. The fluorescent dye did a number on him and he had to try several attempts to shampoo the yellow out.

 

  

 

Even with a majority of the base drilled through, the stromatolite resisted leaving its perch. In the end we ended up wrapping lines around the stromatolite and tethering it to the research vessel. We put the vessel in reverse and revved the engines till we heard the pop that indicated the stromatolite was free. We had divers in the water watching the process from a safe distance. The next step was to haul the stromatolite onto the ship. There was no direct way to get this heavy monolith onboard in one step so we first raised it from the water and placed it on the deck of the small Carolina Skiff we were using as the diving support boat and which held the engine and air tanks for our excavation tools. From there we were slowly able to re-rig and lift this onto the main deck of the ship with the davit on the upper deck used for raising and lowering the Carolina Skiff from its storage area on top. Quite the operation and not without some tense moments and occasional bouts of shouting and screaming. No digits or limbs were lost in the process and the stromatolite (safely wrapped in a plastic tarp) made its way back to the Rosensteil School for Marine and Atomospheric Science (RSMAS) at the University of Miami. The guy below in the blue t-shirt posing with his prizes is Dr. Robert Ginsburg of RSMAS who was the expedition leader, a geologist with a lengthy fascination with stromatolites.

 

  

 

     

 

 

  

 

  

 

 

 

[digit]

We started analyzing some of the smaller samples we'd harvested on the ship during the return trip to Miami. There the stromatolite was dried and stabilized and then sliced on an enormous rock saw into thin sections which allowed the structure of the growth of the stromatolite to be analyzed. As with all science, the field collection is rather quick (the mission lasted only 10 days) while the analysis goes on for years.

 

Here is the mission team posing with our Explorer's Club flag. As mission photographer I managed to stay behind the lens and so I never appear in any of the images--my preferred position is usually 'out of frame'.

 

Hope you enjoyed this little trip report addendum from a decade ago showing just how different the Bahamian stromatolites are to those found in Shark Bay.

 

Cheers.

 

-Ken