Pr

1
Exploring the Holocene through fossil
cyanobacterial sequences from Antarctic core
sediments Rafael Fernandez-Carazo1, Krzysztof
Waleron1,2, Dominic A. Hodgson3, Elie Verleyen4,
Wim Vyverman4and Annick Wilmotte1 1CIP, Institute
of Chemistry B6, University of Liège, B-4000
Liège, Belgium. 2 Department of Biotechnology,
University of Gdansk Medical School of Gdansk,
80-822 Gdansk, Poland. 3 British Antarctic
Survey, NERC, Cambridge, UK. 4Laboratory of
Protistology and Aquatic Ecology, Ghent
University, B-9000 Ghent, Belgium Email
 rfernandez_at_ulg.ac.be
Introduction
The HOLANT project aims to determine how the
climate of coastal (Sub-)Antarctic regions has
varied during the Holocene and study the
ecosystem responses. We have tracked
environmental changes from the cyanobacterial
diversity on the basis of 16S rRNA genes
extracted from sediment cores from 2 lakes (lakes
BK1 and BK2) in Beak Island (Antarctic
Peninsula). Lake BK2 was formed in the relict
outflow streambed of BK1. Lake BK2 shows higher
nutrient concentrations and lake primary
production that might also be related to its
closer proximity to the sea and thus the more
frequent visits by penguins which lead to natural
nutrient enrichment (eutrophization). However,
the dominant benthic phototrophs in these
systems, the cyanobacteria, do not leave
recognizable fossils, making it difficult to
assess their response to past climate
variability.
Material Methods
We have analysed 2 sediment cores taken from
lakes BK1 and BK2 in Beak Island (Fig.1). DGGE
was performed using specific primers for
cyanobacteria. The sequenced bands were compared
to public databases to find their closest
relatives (BLAST, RDPII). Lost on ignition
(LoI550) was analyzed (2) for both lakes. PCR was
realised with several pairs of primers for 16S
rRNA genes (N359F, B23S, 781R (1) and rpoC1 gene
(3F, 4R, 7F, 8R K.Waleron, unpubl. data). Whole
Genome Amplification by Multiple Displacement
Amplification (MDA) was realised using the
REPLI-g kit( Qiagen) (Fig.3).
Fig 2. Scheme of the rpo operon.
Fig 3.Schematic representation of REPLI-g
amplification
Fig 1. Lakes BK1 and BK2.
Filamentous cyanobacteria
Unicellular cyanobacteria
Conclusions
Fig 5. LoI550 graphics for BK1 (left) and BK2
(right)
Fig 4. PCR amplification of fossil DNA from
Progress Lake, using different primers.

• -MDA has been used as effective method for
  amplification of samples where fossil DNA was in
  so low quantities that it could not be detected
  by direct PCR.
• Synechococcus has been frequently detected in the
  cores, maybe due to a higher resistence to
  degradation of this group. This observation was
  already made in the LAQUAN project
  (www.laquan.ugent.be)
• In Lake BK1, the highest diversity is found in
  the upper layers, corresponding to a peak in the
  LoI550. Higher productivity in BK2, indicated by
  LoI550 values (Fig.5), is likely related to high
  nutrient concentrations following lake isolation.
• In Lake BK2, filamentous cyanobacteria belonging
  to the Nostoc group, were present c. 4000 years
  BP, suggesting ecological differences with Lake
  BK1.

Filamentous unicellular cyanobacteria
References (1) Taton, A., S. Grubisic, E.
Brambilla, R. De Wit, and A. Wilmotte. 2003.
Cyanobacterial diversity in natural and
artificial microbial mats of Lake Fryxell
(McMurdo dry valleys, Antarctica) A
morphological and molecular approach. Applied and
Environmental Microbiology 695157-5169. (2)
Birks, H. J. B., V. J. Jones, and N. L. Rose.
2004. Recent environmental change and atmospheric
contamination on Svalbard as recorded in lake
sediments - an introduction. Journal of
Paleolimnology 31403-410.