Magical! Driving a sub through the “herms” of Pavilion Lake is absolutely magical! Imagine this: a snow of particulates streaks around the dome. A yellow light permeates the water column as it filters through the planktonic cloud and bounces through the Chara. Microbialites rise up from the bottom like castles shrouded in a mist of microalgae. The natural world is like poetry to an observational scientist, and a dive in the herms is high art. Of course, to someone who studies the shapes and forms of microbialites (like I do), a dive in the herms is also like candy! Microbialites cover up to 90 percent of the lake bottom, and exhibit a variety of different shapes in a space of only a few meters. For a microbialite scientist – Yum!
View from the pilot's seat.
Today I was lucky enough to pilot such a dive to the herms. The herms are an area near the center of Pavilion Lake. Their name is a bit of a misnomer – in fact, it is more of a nickname that stuck! Herms is short for bioherms, which refers to a build up of biological organisms, usually into a mound that rises above the surrounding sea or lake floor. Our Pavilion herms are mounds, but they are probably just sediment mounds that are covered in lots of microbialites, rather than being mounds build up exclusively by microbialites. Nevertheless, they remain a favorite area of the PLRP scientific team, because of the small area, dense ecology, and interesting geochemical and limnological environment.
My mission was to completely circumnavigate two of the herms that we had not mapped in previous years. Navigating the subs through an area of such dense mounds and interesting features has been challenging in the past. The topography can make communication between the surface and subs problematic, and our maps have not always been as accurate as they are now. However, as our research has continued, our knowledge of the area has improved, our communications infrastructure has grown by leaps and bounds, and I daresay, some of us are even getting better at flying these subs! I am proud to say that the circumnavigation went smoothly and we were able to fill in some missing areas in our maps of the herms!
Exploring the herms at 40 feet.
Improving our maps also means raising more questions; such is the nature of exploration, and this dive was no exception. Although many of the morphological trends that I observed were similar to those I have noticed before (adding strength to some of our hypotheses), new subtleties leapt into view. Why, for example, do many of the microbialites along the bottom of the mounds look roughed-up, slightly broken, whitish, and all together kind of crummy? Does it have to do with fluctuating sediment levels at the bases of the mounds? Perhaps. That leads me to questions of how precisely sediment is transported around the mounds: what is the source of the sediment? How often do large sediment flows come down from the surrounding walls? Are the microbialites buried and exposed regularly or does it happen on a timescale of decades or centuries!? For each answer there are new questions, and for each new question there are a handful of associated questions.
Returning to the surface to see a smiling Susan Winnitoy, guiding me back to the barge.
The abundance of new questions is thrilling, and is what keeps bringing us back here. I often find myself chatting with people who are surprised that we haven’t uncovered all of the details of microbialite formation, development, and growth – after all, we have been studying Pavilion Lake for a number of years. Yet that is the appeal of studying microbialites! Microbialite mounds are subject to nearly countless variables – biological, chemical, and physical processes that change through time. Untangling each of those influences is a process – a process that is being helped along by the phenomenal amount of data that we are collecting with the DeepWorker subs, with the GAVIA AUVs, and with our team of SCUBA divers. So, do we understand everything about microbialite formation yet? Nope. Not by far. But with dives like my magical one through the herms, we are getting ever closer! The microbialites of Pavilion Lake have a story to tell, and through our exploration we are listening to the telling.
- Bekah
