Microbiology of Mt. Erebus
Antarctica, best known for its extreme cold and glaciers, harbors a few active geothermal sites. The largest of these is Mt. Erebus, located on Ross Island. Mt. Erebus (3,800 meters tall; 12,500 ft) is the southernmost active volcano in the world and houses an active lava lake in the middle of its Main Crater. This same lava lake also produces daily strombolian eruptions. There are a variety of geothermally active sites across the summit of Mt. Erebus, in addition to the lava lake, which are generally concentrated in a few large sites. The hot soil and steam from the volcanic activity at these sites collides with the extremely cold air around Mt. Erebus (never warmer than -20C in the summer), resulting in a variety of magnificent features, such as ice towers, ice caves, and ice hummocks. Mt. Erebus is also a phonolitic volcano, which gives the summit a geochemical composition only found on a few other volcanoes. It also experiences prolonged periods (3+ months) of complete darkness every year during the winter.
What sorts of microorganisms inhabit this extraordinarily harsh environment? How do these microorganisms make a living? Have the isolated and unique geochemical nature of Mt. Erebus led to endemic microorganisms on Mt. Erebus? Do the microbes living there possess novel metabolisms? These are the sorts of questions that we are attempting to answer in the MAGMA Project (Multidisciplinary Analysis of Geothermal Microbes in Antarctica), of which I am the lead postdoc.
Read more about the MAGMA Project and follow along with our fieldwork on our Facebook page.
The first samples from the MAGMA project were collected in 2019 by several members of the team from two geothermal sites on the summit of Mt. Erebus: Tramway Ridge, a relatively sheltered site with hot soil and lots of active fumaroles and moss mats; and Western Crater, a very exposed site with hot soil covered by ice hummocks and no moss mats. We analyzed the microbial communities at the two sites and found them to be starkly different, with Tramway Ridge having much more archaeal species (known for metabolizing ammonia, a nitrogen-containing compound) than Western Crater, among other differences. Although the sample sets we analyzed were collected along temperature gradients (from ~60C down to ~20 C), pH, not temperature, was the primary soil chemistry factor that influenced the composition of the microbes living there. This was because Tramway Ridge had a significantly lower pH (~4-6) than Western Crater (~7-9). This research was published in 2022 (https://doi.org/10.3389/fmicb.2022.836943).
Comparison of the microbial community across temperature gradients at two sites on Mt. Erebus: Tramway Ridge (TR) and Western Crater (WC), showing the higher proportion of archaea at TR and higher proportion of unknown microbes at WC. Two transects were collected at TR. Figure 4 from Noell et al., 2022.
In addition to the samples from 2019, we also possess a large number of older samples from a variety of sites both around Mt. Erebus, as well as from other Antarctic geothermal sites (Mt. Melbourne and Mt. Rittmann, located over 1,000 km away from Mt. Erebus).
In 2024, we published a survey paper of the biota of Mt. Erebus across all domains of life from all known large geothermal sites on Mt. Erebus, from ice caves to hot soils. We found that communities of bacteria, algae, and fungi at subglacial sites (i.e., those at cooler temperatures that are covered by ice for most of the year, such as ice caves) were quite similar to each other, despite being found scattered all over the Erebus summit. At higher temperature sites (>40 C), however, communities tended to be quite different from each other depending on the site from which they came. This is the first comprehensive, all-domain survey of biota on Mt. Erebus. You can find this research online at FEMS Microbiology Ecology: https://doi.org/10.1093/femsec/fiae128
Some images of sites from our Erebus survey paper. Top left: the entrance to the ice cave called Helo Cave. Top right: soil sampling on Side Crater. Bottom left: entrance to Warren Cave. Bottom right: Hut Cave.
We also conducted a comparison between two of the largest sites on Erebus (Tramway Ridge and Western Crater) and other geothermal sites in Antarctica (Mts. Melbourne and Rittmann). We found that the microbial communities at Mt. Melbourne were very similar to those at Western Crater on Erebus, despite the over 1,000 km of ice separating the sites. The communities at Rittmann and Tramway Ridge were distinct from each other and from Melbourne and Western Crater, likely driven by unique features of each site (Rittmann is quite steep and has shallow soil, while Tramway Ridge has a lot higher productivity and thus more carbon and nitrogen). We also found that there were few to no shared microbes between all of these sites, despite strong ecological evidence of dispersal between these sites. You can read more about this research in our preprint, located on biorXiv until the peer review process is complete: https://www.biorxiv.org/content/10.1101/2024.06.06.597824v2.abstract
Sampling at Mt. Melbourne (left) and Rittmann (right) in 2014.
All our past research has found that the microorganisms inhabiting Mt. Erebus are quite unique globally. However, in order to truly know what these microbes are doing in the environment, we need to bring them back into the lab and grow them so we can study them. Towards this end, in November 2023, our team conducted two drilling operations at geothermally heated soils on Mt. Erebus, with the goal of culturing some of the very unique microorganisms that inhabit these remote and difficult-to-access sites. Our team returned in November 2024 to retrieve overwinter incubations and start new cultures with fresh samples, using lessons learned from 2023 to fine tune our approach.
Images from our 2023 season: installing our temperature logger at Western Crater (top left); drilling at Tramway Ridge (top right). At work in the lab at Scott Base that we set up (bottom left). Some cells we cultured (bottom middle); some of the Firmicutes that we cultured (bottom right).