Moments ago I finally submitted the final frost flower paper from my PhD, a paper which first found life as Appendix 2 in my dissertation. Once upon a time I thought this particular project was going to be the central pillar of my doctoral work. It didn’t quite work out that way, but I’m really glad to see this manuscript go off into the world. I wish it well.
Most of the frost flower and young sea ice work that I conducted with my adviser, Jody Deming at the University of Washington, took place in the Arctic. Starting all the way back in 2009 (and thanks to collaborators in the OASIS project – a collaboration that, in retrospect, we should have worked harder to maintain) we sampled frost flowers and young sea ice during the winter and spring near Barrow, Alaska. Near Barrow an offshore polynya, part of the circumpolar flaw-lead system, provides access to a region of ice formation all through the winter. The fickle nature of the polynya and issues with access and timing however, lead us to consider other possibilities. At about the same time I got interested in a series of papers suggesting that frost flowers could be the source of sulfate depleted sea salts in coastal Antarctic glaciers. Repeatedly skunked on Barrow sampling trips and with the pressure mounting to develop a thesis topic I hatched a plan to develop a biological side to this sea salt story. If frost flowers were responsible for transporting salt to the Antarctic interior, and our work had demonstrated that frost flowers were enriched in bacteria, it stood to reason that bacteria would be transported as well. This could link the marine and glacial microbial environments in a previously unexplored fashion, with implications for gene flow to and microbial habitation of the expansive glacial environment.
We proposed all this to NSF and received partial support to conduct a pilot study (see NSF award 1043265). Our efforts the following (2011) field season are well documented in the earliest entries on this blog, starting here. After major bureaucratic delays (the McMurdo Station personnel were very reluctant to allow sampling in the young sea ice zone), blizzards, injuries, mishaps involving Weddell seals, and various other trials and humiliations that I’ve probably purged from my memory we emerged from Antarctica with samples of ice from the surface of Taylor and Wilson-Piedmont Glaciers, snow, frost flowers, newly formed sea ice, and seawater. Our plan was to sequence the 16S rRNA gene from DNA extracted from these samples (a standard way of describing community composition and structure in microbial ecology) and look for overlaps. Abundant frost flower microbes that also appeared in glacial ice, for example, would indicate that our proposed transport mechanism was active.
The author collecting frost flowers and young sea ice from Lewis Bay on the north side of Ross Island, October of 2011.
Our first sequencing effort was a complete disaster. Weeks of work went down the drain with our primary samples. It still isn’t clear where things went wrong; in our lab, at the (nameless if not blameless) sequencing center, or both. My money’s on both. Thankfully we had a limited set of backup samples and just enough funding left to try one more time. This time we switched from the 454 to the Illumina sequencing platform, and placed our samples in the capable hands of the sequencing center at the Argonne National Lab. A few weeks later we had data. By this time, however, I’d moved on to other things and was cramming to finish the existing chapters of my dissertation. Such is the way things go. I had just enough time to do an initial workup and staple it to the back of my dissertation as an appendix so that it would at least exist somewhere if I never got back around to it.
Fortunately I have a couple of frightening manuscript deadlines coming up, and there is no better way to deal with an impending deadline than to ignore it completely and find something else to do. In this case reforming the half-baked appendix into a proper manuscript (and then writing a blog article about it) was the perfect avoidance mechanism (tomorrow I’m on it).
With the back story complete, what did we find in the Antarctic frost flowers? Definitely not what we initially expected. We found very little evidence of marine bacteria being deposited and preserved in either glacial ice or snow (this doesn’t mean they aren’t transported there, they probably just don’t survive the trip or last long when they get there). We did, however, find a significant number of terrestrial bacteria in frost flowers samples, particularly cyanobacteria of the genus Pseudanabaena (commonly found in melt pools on the surface of glaciers) and an add assortment of non-marine sulfur oxidizers. We think that all of these are the result of wind-driven transport from land the the ice surface, with the latter coming from the sulfur-rich environs around volcanic Mt. Erebus. What all this means for the microbial ecology of the sea ice surface is not clear. Armed only with 16S rRNA gene sequences we can’t do much more than speculate. Further work will have to be done to see if these bacteria are doing anything of interest at the ice surface.
It is worth noting that we have now published community structure data from frost flowers from three different environments, and that the story behind each is very different. In our earliest efforts at Barrow we collected frost flowers from a highly productive coastal system and found a strange assortment of putatively marine Rhizobiales. We went to some pretty great lengths in a 2014 paper to demonstrate that these don’t look like terrestrial Rhizobiales deposited by wind, and at any rate the Barrow coastline was pretty well covered with snow when we were there. In later efforts at Daneborg in Greenland, Jody Deming and a team of collaborators collected frost flowers from a highly oligotrophic fjord. We found that the microbial community in these looked pretty much like the community in seawater. Last, we know have these odd frost flowers from off Ross Island in Antarctica, which appear to contain some very interesting bacteria from various adjacent environments. So the overall story seems to be that the sea ice surface – a warmer and more chemically active environment than one might think – can harbor a diverse array of bacteria. Which bacteria and from where depends heavily on the dynamics of the surrounding area, including what’s happening in the water when the ice forms, the extent of snow cover, wind magnitude and direction, and probably some things we don’t know about yet!
For my postdoc I’m firmly out of young sea ice and into the water column, looking at microbial processes around the West Antarctic Peninsula. Someday, however, it will be good to get back around to young sea ice. If published this will be our fifth paper on the subject and I feel like we hardly have any answers!
