Comparative functional biodiversity of Antarctic and Arctic Sea Ice Communities
Final Report Abstract
Aim of the project was a comparison of the functional biodiversity of Antarctic and Arctic sea ice communities using 18S amplicon sequencing and transcriptomics. Sampling was planned in both areas on the occasion of Polarstern cruises ANT-XXVIII/2 (PS79) and ARK-XXVII/3 (PS80/3). The project had an initial major drawback because the first sampling cruise, i.e. the Antarctic part, unfortunately was a complete failure due to an accident. Before sampling could start, both helicopters necessary for the expedition crashed in bad weather, one of them having the doctoral student onboard. Furthermore no further Antarctic ice sampling was possible, neither for us, nor for other members of the expedition; therefore we had to conduct the project with only the arctic samples. Accordingly the work program was extended to the isolation of uni-algal sea ice diatoms with subsequent physiological and transcriptomic profiling. Except for the missing Antarctic sampling, the project achieved what we aimed for. Biodiversity profiles based on DNA and on RNA were established and analyzed in detail. We found that the nature and age of sea ice has a strong influence on the biodiversity, furthermore significant insights into the communities have been gained by comparing 18S amplicon sequences based on environmental DNA versus RNA. The latter, presumably “active” biodiversity, was e.g. enriched for Melosira in multi-year ice and for heterotrophic alveolates in melting sea ice. This has implications for future warmer scenarios with decreasing multi-year ice and an earlier onset of sea ice melt. We were able to isolate up to 4 sea ice diatom strains into uni-algal cultures and to identify them based on their 18S sequence. One of the species, being most similar to naviculoid diatom CCMP2297, has been chosen for a more detailed analyses because its 18S sequence was dominant in our 18S amplicon database, therefore likely representing an important part of the natural sea ice community. The diatom was able to tolerate a temperature range between -5 and +5°C, but died at 10°C. Transcriptomic profiling allowed for detailed insights into the response of the diatom to elevated temperatures. It appeared that already a temperature of 5°C is a challenge for the species on the transcriptomic level altough its physiology seems to be unaffected. Finally meta-transcriptomes from three samples were generated for which we also have rRNA and rDNA based 18S data. These will serve as basis for future analyses of whole community genes expression and the in situ gene expression of individual species such as isolate CCMP2297 or Melosira arctica for which we recently established a draft genome sequence.
Publications
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(2015) rRNA and rDNA based assessment of sea ice protist biodiversity from the central Arctic Ocean, European Journal of Phycology
Stecher, A., Neuhaus, S., Lange, B., Frickenhaus, S., Beszteri, B., Kroth, P. G. and Valentin, K. U.
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“Functional biodiversity of sea ice-associated protists in the central Arctic Ocean” Dissertation, Department of Biology, University of Konstanz, 2015
Anique Stecher
