Well, on Monday night I had great fun sharing my dirty secrets about microbes and glaciers with a lovely crew of people who turned up to the Aberystwyth Science Café.
Rather than rehash what I said, I thought it might be fun to report some of what the audience asked me at the end of the talk or at the bar. I was really humbled by the interest and pertinence of the questions, which came from a diverse and varied audience. I could recognize many eminent experts in palaeoglaciology, sedimentology, bioinformatics, mycology and botany in the audience, as well as a range of students and people just curious about all of this glacier bugs malarkey. So here’s what I could remember, as I remember it (a government health warning if there ever was!).
I’ve now edited to link to peer reviewed papers supporting my responses and fix typos.
1. Does human pollution affect glacial ecosystems?
Yes. Five kinds of pollution in particular:
Nitrogen – a single deposition event from air masses rich in anthropogenic nitrogen oxides blown up from Europe can meddle with an entire glacial ecosystems. Microbes in Arctic cryoconite no longer need to fix nitrogen for themselves, so long as deposited nitrogen from the snowpack reaches them. This has been a major change for glacial ecosystems in since Messers Haber and Bosch radically altered our nitrogen economy.
Radionuclides – from accidents and atmospheric nuclear tests. Alpine cryoconite is the most-enriched substance beyond test sites known to science. You can detect the radionuclide signatures of particular events even.
Mercury – Microbes in High Arctic snow have to deal with mercury contamination, and their plasmid genomes reflect this.
Persistent organic pollutants. Mainly on glaciers heavily used for skiing and recreation. Some cryoconite microbes seem very capable of bioremediating these pollutants.
Antibiotics – genes for antibiotic resistance are found on many glaciers.
2. Nature always tries to find a balance. Are the microbes in glaciers collaborating, competing etc?
Yes. Cryoconite, for instance, is a collaboration between phototrophs and heterotrophs. But there’s also lots of competition and bug-eat-bug stuff going on. In particular the viruses – these are highly abundant and their tendency to kill most of the bacteria but produce very few progeny – makes for one of the biggest viral shunts of the microbial loop known. Protozoal grazers are also important.
3. Is the effect of microbes on glaciers being accounted for in models of environmental change?
Not as far as I know, and they probably should be. We have produced climate-reconstruction dependent models of glacier carbon cycles, but how ice-microbe-albedo feedbacks and carbon cycles interact with climate seem to be ignored. An exception is a paper by Jan Oerlemans’ group which suggested that supraglacial dusts induce a melting effect equivalent to an additional +2 degrees Celsius above that from warming predicted by common climate models on Alpine glaciers.
4. What happens to the cryoconite when it goes into the sea as icebergs calve?
This is one of the important questions we have yet to answer fully about how microbes on glaciers influence ecosystems “downstream” – be they terrestrial (glacier forefields), fluvial (streams) or marine. We know that in some marine systems (such as the Gulf of Alaska) that glacial organic carbon is the major source of organic carbon flux from land to the sea, but uncertainty surrounds the origins of that carbon.
5. How active are the microbes in cryoconite?
Surprisingly so. Rates of microbial activity in cryoconite (sat at 0.1-1 degrees C) have been compared to Mediterranean soils. We still lack really comprehensive, definitive audits of the cryoconite economy as it varies through space and time though.
6. Do they stay active if cryoconite is buried in the ice?
I don’t know. We’ve thought about this, and have some ideas from labwork about dormancy and resuscitation we’d love to test, (as an undergrad I studied in a lab which did a lot of this work) but we never made a sufficiently compelling case to be funded enough to find out in the real world.
7. The surface of one of Jupiter’s moons, Europa is water ice, and it’s coloured. Is that microbial pigments?
I honestly don’t know. It’s an interesting possibility, but it’s kind of beyond my logistical capabilities to organise a field trip there. I know there are many dedicated researchers working on astrobiology, and agencies which fund cold ecology as an analogue for extraterrestrial life, but I have to admit that I find more pressing concerns closer to home: The one planet we know supports rich and biodiverse life is experiencing warming which first affects the 80% of its biosphere which is colder than your fridge, and we have yet to find all of life on Earth, as we know it.
7. What does life on mean for primary succession in glacier forelands?
It means that it probably isn’t really primary succession. See an earlier blog post of mine which covers aspects of this issue.
8. When does the bar open?
Ages ago. Mine’s a pint. Cheers!
My thanks to the 65 or so people who attended and paid attention to my absurd ramblings, and asked the questions above.