Antarctica is Earth’s most pristine and geographically isolated continent. While 99% of its terrestrial area is ice-covered, freshwater habitats scatter the ice-free oases near the coast, representing important habitat for Antarctic biodiversity. Currently, rapid climate changes are fundamentally transforming these limno-terrestrial habitats, and at the same time, Antarctic diversity remains critically under-documented due to the majority of it being microbial. Of the microbial eukaryotes, diatoms (single-celled siliceous algae) are likely the most diverse. Diatoms have been widely studied from Antarctica using morphological methods, yet they have been rarely studied using molecular methods (e.g. DNA metabarcoding) despite widespread cryptic diversity within this group. As a result, we are only beginning to get a sense of Antarctic diatom diversity, community assembly, and biogeography. This contrasts strongly with the application of diatoms in biomonitoring and as ecological proxies, and combined with the imminent impacts of climate change makes their study particularly urgent.

Using a combination of new and archived samples, the focus of this doctoral thesis will be to:

1) Compare morphological/molecular diatom diversity from different habitats and regions,

2) Characterize and quantify diatom community assembly processes with DNA metabarcoding, and

3) Synthesize results to project how communities will shift with climate change.

Five relevant publications of the research group:

Kollár, J., Kopalová, K., Kavan, J., Vrbická, K., Nývlt, D., Nedbalová, L., Stibal, M. and Kohler, T.J., 2023. Recently formed Antarctic lakes host less diverse benthic bacterial and diatom communities than their older counterparts. FEMS Microbiology Ecology, 99(9), p.fiad087.

Michoud, G., Kohler, T.J., Ezzat, L., Peter, H., Nattabi, J.K., Nalwanga, R., Pramateftaki, P., Styllas, M., Tolosano, M., De Staercke, V. and Schön, M., 2023. The dark side of the moon: first insights into the microbiome structure and function of one of the last glacier-fed streams in Africa. Royal Society Open Science, 10(8), p.230329.

Kohler, T.J., Singley, J.G., Wlostowski, A.N. and McKnight, D.M., 2023. Nitrogen fixation facilitates stream microbial mat biomass across the McMurdo Dry Valleys, Antarctica. Biogeochemistry, pp.1-22.

Brandani, J., Peter, H., Fodelianakis, S., Kohler, T.J., Bourquin, M., Michoud, G., Busi, S.B., Ezzat, L., Lane, S. and Battin, T.J., 2023. Homogeneous environmental selection structures the bacterial communities of benthic biofilms in proglacial floodplain streams. Applied and Environmental Microbiology, 89(3), pp.e02010-22.

Kohler, T.J., Howkins, A., Sokol, E.R., Kopalová, K., Cox, A., Darling, J.P., Gooseff, M.N. and McKnight, D.M., 2021. From the Heroic Age to today: What diatoms from Shackleton's Nimrod expedition can tell us about the ecological trajectory of Antarctic ponds. Limnology and Oceanography Letters, 6(6), pp.379-387.

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