Nanoplankton assemblages in maritime Antarctic lakes: Characterization and molecular fingerprinting comparison

UNREIN, F.; IZAGUIRRE, I.; MASSANA, R.; BALAGUÉ, V.; GASOL, J. M.

AQUATIC MICROBIAL ECOLOGY

Inter-Research

Año: 2005 vol. 40 p. 269 - 282

0948-3055

The composition of planktonic eukaryotes in the size fraction 3–20 μm of 10 maritimeAntarctic lakes was studied by denaturing gradient gel electrophoresis (DGGE). Microscopic observationswere also carried out to compare the results obtained by this molecular fingerprinting techniquewith morphological data. Six lakes from Hope Bay (Antarctic Peninsula) and 4 from the PotterPeninsula (King George Island) were sampled during the austral summer of 2003. These lakes wereof different trophic status and covered a wide range of limnological features. Previous studies of theplanktonic communities of these lakes revealed high nanoflagellate abundance and biomass, buttheir taxonomic identification was usually uncertain due to their similarity in size and shape. Here,the application of DGGE allowed both a comparison of the structure of the nanoplanktonic communitiesand an identification of the dominant populations through sequencing of the most prominentDGGE bands. The most important organisms in these lakes were the Chrysophyceae, represented inthe DGGE gel by 5 different band positions and identified by microscopy in 5 different morphotypes,including uniflagellated and biflagellated naked organisms: 1 sequence belonged to the Chrysosphaerales,2 closely related bands (likely 2 species from the same genus) belonged probably to theOchromonadales (unicellular biflagellates), while the other 2 bands could not be assigned to anydefined chrysophyte group. Sequences related to Chlorophyceae, Bacillariophyceae and probablyCercozoa were also retrieved. A Dictyochophyceae belonging to the order Pedinellales is reported forthe first time in freshwater Antarctic ecosystems. Microscopic observations suggest that this phytoplanktonicorganism most likely corresponds to Pseudopedinella. Most of the lakes shared severalcommon sequences, such as 2 chrysophyte bands, which suggests the existence of well-adaptednanoplanktonic species dispersed throughout the Antarctic lakes. However, some sequencesappeared exclusively in specific lakes, which seems to be related to the trophic status of the waterbodies and probably also to the local conditions of the maritime Antarctic regions sampled.