Distribution of diatoms in surface sediments of 33 lakes in southern Patagonia, Argentina

ECHAZÚ, D. M.; MAIDANA, N. I.

CABA

Workshop; 1ª Reunión Internodos del Proyecto Interdisciplinario Patagonia Austral y 1er Workshop Argentino del Proyecto Potrok Aike Maar Lake Sediment Archive Drilling Project; 2010

ANPCYT

Diatoms are valuable tools for paleoclimatic reconstructions due to their sensitivity to climatically controlled environmental parameters, assuming that the organism- environment relationships have not changed, at least since the late Quaternary. The development of transfer functions, one of the numerical techniques more used for paleoenvironmental reconstruction requires a "training set" developed from the survey of regional biodiversity. Thus, environmental information collected from living forms can be extrapolated to the fossil record. Santa Cruz is one of the argentinian provinces least known in their non-marine algal communities. Within the limited existing information for the province, the recent and fossil diatoms are the group that has received most attention (Krasske, 1949, Luchini, 1975; Maidana & Corbella, 1997; Maidana et al., 2005 and Espinosa, 2008, among others). The development of a training set for water bodies located in the south of the province is an indispensable tool to understand the ecological requirements of living species and provide relevant information for understanding the evolution of past environments, not only for the Laguna Potrok Aike sourrounding area (object of the ICDP-PASADO project), but also for the entire Southpatagonic region. On the other hand, the results will increase significantly our knowledge of diatom biodiversity at the region, which is of great importance in implementing protection and conservation of natural resources strategies. To achieve our objectives, water and surperficial face sediment samples were obtained from 33 permanent lakes and ponds in Southern Santa Cruz Province (50 º-52 º S, Fig 1) during the two sampling campaigns (January/2009 and febrero/2010). In each environment we measured in situ pH, temperature, water conductivity, dissolved solids and dissolved oxygen. The chemical analysis of water samples were performed at the CNR-ISE (Italy). The diatom analysis was conducted at the Laboratorio de Diatomeas Continentales (DBBE, FCEN-UBA) and standard techniques were applied, including oxidation of the organic matter with H2O2 (Battarbee, 1986). Permanent slides were mounted with Naphrax®. For the taxonomic identification of diatoms we have consulted the standard floras of Rumrich et al. (2000) and Van de Vijver et al. (2002), as well as several other specific works. For the estimation of the relative abundances, a minimum of 400 valves was counted per preparation.