Abstract :
[en] A. Context
Little is known about the diversity and geographic distribution of biota in Antarctica.
This is in part underlain by the lack of systematic sampling and geographical coverage,
and the problems associated with species definition, cryptic diversity and cultivability.
Particularly the Dronning Maud Land region is understudied in terms of its biodiversity.
As a result, we largely lack the ‘baseline’ data needed to understand the contribution of
various processes that are responsible for the geographical patterns present in the
diversity and composition of microbiota, lichens, mosses and microinvertebrates and to
observe possible future changes in their diversity and taxonomic composition due to
ecosystem change and/or human introductions.
B. Objectives
BELDIVA is aimed at (i) obtaining a first integrated biological description of the pristine
habitats in an area of 50 km around the Belgian Princess Elisabeth research station (Sør
Rondane Mountains) using state-of-the art sequencing techniques and (ii) studying their
response and adaptations to change and the factors that control their spatial distribution.
BELDIVA has the following scientific objectives:
1. Study the importance of airborne propagules in shaping the diversity of terrestrial
and aquatic habitats in the Sør Rondane Mountains;
2. Install Open-Top Chambers to mimic future climate warming and its effect on the
microbial communities;
3. Study adaptations under the extreme Antarctic conditions by conducting in situ
experiments (i.e., photosynthetic efficiency).
4. Study the deglaciation history of the region, which will put the biodiversity data into
a temporal framework.
5. Study the biodiversity of microorganisms (both prokaryotes and eukaryotes),
microinvertebrates, lichens and mosses in various habitats in the region with a
particular focus on soils;
6. Verify the distribution in representative samples of particular bacterial and
cyanobacterial taxa and to integrate our findings with results obtained within other
projects
C. Conclusions
Back trajectory analysis of air masses in East Antarctica revealed that longdistance
transport of microorganisms is possible within the continent and evenbetween continents during cyclone events. However, the concentration of biotic
propagules appeared to be low in the filters studied.
A total of 8 Open top chambers (OTC) on four different nunataks/ridges were
installed. Monitoring revealed that the temperature was up to 5.8°C higher than
the temperature outside of the OTC between 2010 and 2012. In some cases the
temperature was higher outside the OTC, probably as a result of the longer
persistence of snow in the OTC leading to a more buffered temperature regime.
No significant change in vegetation cover could be observed over this relatively
short period. A follow-up study is recommended to assess the effect of climate
warming on these soil crusts.
Measurements of the photosynthetic efficiency revealed that cyanobacteria were
probably photosynthetically active even at the temperature -7.8°C.
Cosmogenic isotope dating revealed that all samples analysed so far have a
complex exposure history with samples surviving more than one glacial cycle.
Erosion-rates are large in both studied regions, indicating they have all
experienced a high degree of recycling, long periods of burial and/or multiple
periods of exposure, resulting in large burial age ranges and large age errors.
Among the prokaryotes, Cyanobacteria, Proteobacteria, Bacteroidetes,
Acidobacteria, FBP, and Actinobacteria were the most abundant prokaryotic
phyla in 22 samples studied using 454 NGS from soils, lakes, cryoconite holes,
and endolithic habitats. Multivariate analyses revealed that the prokaryotic
community structure in lakes was significantly different from those in dry soils
and endolithic habitats.
Morphological observations and DGGE analysis of crust samples revealed the
presence of 15 morphotypes and 26 OTUs in Cyanobacteria of which the most
abundant were related to Phormidium autumnale/Microcoleus autumnalis,
Cyanothece aeruginosa, Tolypothrix, Nostoc, Leptolyngbya sp. and
Phormidesmis pristleyi. These analyses also showed a higher diversity on granite
rocks than on gneiss. Only 15% of the OTUs (defined with a threshold of 97.5%
of 16S rRNA similarity) appeared limited to Antarctic habitats.
Ordination analyses revealed that total organic carbon was the most significant
parameter in structuring the prokaryotic communities studied using the Illumina
technology, followed by pH, conductivity, bedrock type and water content.
Acidobacteria (Chloracidobacteria) and Actinobacteria (Actinomycetales)
dominated the organic carbon poor samples situated on gneiss, while
Proteobacteria (Sphingomonadaceae), Cyanobacteria, Armatimonadetes and
candidate division FCB (OP11) mainly occurred in granite samples with a high
total organic carbon content OTUs belonging to the Rotifera, Chlorophyta, Tardigrada, Ciliophora, Cercozoa,
Fungi, Bryophyta, Bacillariophyta, Collembola and Nematoda were present with
a relative abundance of at least 0.1% in the eukaryotic communities as assessed
using the 454 NGS of the 22 samples from various habitats in the region.
Multivariate analyses revealed a lack of differentiation of eukaryotes according to
habitat type (aquatic versus terrestrial).
DGGE analysis revealed the presence of the Chlorophyte genera Stichococcus,
Pleurastrum, Trebouxia, Prasiola, Ulotrix, Diplosphaera, Neospongiococcum,
Xylochloris, Rosenvingiella, Planophila, and Hemichloris in a selection of soil
samples
Fifteen species of lichens and lichenicolous fungi were newly collected in the Sør
Rondane Mountains, raising the total number of taxa known for the Sør Rondane
Mountains to 25.
In some groups, such as the lichens and the chlorophytes, a relatively large
number of taxa/OTUs appeared to be restricted to Antarctica or new to science.
For example, 48% of the lichen flora is endemic to the continent. This supports
the hypothesis that the study area could have acted as a biological refuge during
past glaciations or that the organisms colonized the regions from other ice-free
refugia in Antarctica after the Last Glacial Maximum.
An unbalanced sampling effort in the region due to logistical constraints
prevented an in-depth and standardized analysis of the diversity in the different
nunataks surrounding the Princess Elisabeth Base. Hence, we could not
unequivocally assess which region is most diverse in the different taxonomic
groups studied. However, on Utsteinen Ridge, we recommend that the plots 17
to 21 (from 71°56’48.6”S, 23°20’47.9’’E to 71°56’44.5”S, 23°20’41.8”E) need
careful protection from any human activities in the near and far future given their
high lichen species diversity. In addition, the Pingvinane nunataks appeared to
be rich in biota.
Additional sampling is needed to further investigate terrestrial and aquatic
community structures and elucidate the interactions under the current
environment conditions, as well as differences in the diversity of the different
nunataks. The microtopography is also probably very important to explain the
diversity patterns. A more detailed and extended investigation of the
environmental parameters present can give the necessary insights in the nearly
82 % of the variance that could not be explained with our limited set of
parameters in the ordination analysis of the soils and crusts. The latest
metagenomics and metatranscriptomics approaches would also provide in-depth
insights in ecosystem functioning (i.e. interactions between the different Domains of Life) under the extreme environmental conditions governing this region. This
would not only provide us with these ameliorated insights, but would also allow
for better predictive power in potential changes associated with Global Change.
