INVESTIGADORES
LECOMTE Karina Leticia
congresos y reuniones científicas
Título:
DIATOM COMMUNITIES OVER A CONDUCTIVITY GRADIENT FROM THE PONDS OF CLEARWATER MESA AND VEGA ISLAND, ANTARCTIC PENINSULA
Autor/es:
KOPALOVÁ, K; SOUKUP J; KOHLER TJ; VIGNONI PA; LECOMTE K.L.; CORIA SH; COLMAN D; LIRIO J.M.
Lugar:
Praga
Reunión:
Encuentro; 11th Central European Diatom (11th CED); 2017
Resumen:
James Ross Island (JRI), located on the northeast Antarctic Peninsula, is representative of one of the fastest changing regions on earth, and harbours numerous ice-free areas, lakes, and ponds. JRI also represents an important biogeographical transition zone for limno-terrestrial diatoms, including taxa typical of both the Antarctic Continent and Peninsula. However, it is unknown at this time what conditions create this boundary, and what specific physical and/or chemical characteristics in addition to spatial barriers promote diversity and different community types.Clearwater Mesa is an ice free oasis on JRI located at the southeast side of Croft Bay, and has more than 50 lakes and ponds that remain relatively unexplored. Vega Island is located across the bay from Clearwater Mesa, and is the site of numerous, on-going investigations into the paleolimnology of the region. At these localities, melt-fed lakes and ponds are located within shallow depressions (no more than a few meters deep) formed by glacial erosion, and are often hydrologically connected by small streams. Interestingly, these waterbodies exhibit a wide gradient in conductivity, with closed basin lakes having the highest values, providing a natural gradient in which to test the preferences of diatoms.In this study, we analyse the diatom communities of six lakes sampled from this region to fill a gradient in conductivity. Five lakes in total were sampled from Clearwater Mesa. Of these five, three were sampled from the top of the meseta. Katerina, the biggest lake with relatively low conductivity and high hydrologic connectivity, Soledad, which was isolated with more intermediate conductivity, and Adriana, which had a relatively high altitude and very high conductivity. Two lakes were found at lower altitude and close to the two glaciers surrounding Clearwater Mesa, Florencia and Cecilia, located in depressions formed by glacial deposit. Lastly, two lakes, Pan Negro and Esmerelda, were also sampled from Vega Island. For all water bodies (collected over January 2014 and 2015), the benthos (upper layer of sediment) and epilithon of five of these lake and ponds were sampled for diatoms community characterization. In addition to this, bacterial communities (which create the mat-matrix diatom habitat), physical parameters (ex. area, perimeter, altitude), and chemical variables (pH, conductivity, water chemistry) were also characterized to explain variability in diatom communities. Diatoms were characterized by counting at least 400 valves from each sample, and bacterial communities were evaluated by extracting nucleic acids and sequencing the 16S rRNA gene. We found bacterial communities to be very similar between the six sites, and were mostly comprised of members of Bacteroidetes and Proteobacteria. Despite similarities of the bacterial matrix, diatom communities were radically different between sites, and comprised of species typical of the region. Pan Negro, Esmerelda, and Soledad where dominated by the genus Nitzschia. Katerina also had high proportions of Nitzschia, but this site had greater richness and evenness than the other sites. Meanwhile, Cecelia epilithon had the greatest richness with 22 species, with the genus Achnanthes and Achnanthidium were in highest abundance, and the genus Planothidium was in greatest abundance in Florencia. Adriana, the site with the highest conductivity, was almost exclusively consisting of Denticula, and species richness was the lowest of all lakes.The results from this study provide a better understanding of the physio-chemical controls on diatoms communities from JRI, and will both help to inform ongoing paleolimnological investigations in the region. Furthermore, this work will help investigators predict future changes that make take place, as well as aid in disentangling the evolution of other areas in Antarctica currently and previously ice-covered.