Abstract

Important changes in diatom species composition occur in lake cores globally. Laguna del Maule(LdM), located in a volcanic field (Chilean Andes, 36°S-70°W, 2.160masl) offers an opportunity to investigate if changes are responses to regional temperature or other variables. We quantified species fingerprints by using in diversity and evenness correlated to multiproxy summer (winter) surface air temperature field reconstructions for southern South America. Using a species relative abundance data that spans >700 years (1300 – 2011 AD) we found that Shannon-H diversity (H) and Evenness-J (J) index of the community show the following patterns when compared with austral summer (winter) surface air temperature. A rapid cooling during the Little Ice Age (LIA) since end of 1300’s until beginning of 1900’s is coeval with a drop in H and J, although these peak at mid-1600’s. From c. 1850 until 1900 AD, a warm period, H and J are low. Community parameters rise afterwards and peak at beginning of 1900’s, when temperatures decreased; but then these descend until mid-1900’s when temperature were higher. Since then, parameters rised until today. Anthropogenic impacts like dam construction (1945 AD) and increasing temperatures could be responsible for the increasing diversity. These results suggest that diversity and evenness increase when temperatures were lower and decrease with warming. Fluctuations of H and J during LIA indicate rapid changes within this relatively colder/wetter period. Our results highlight the importance of regional climate drivers on LdM diatom community structure and suggest a significant role for temperature at centennial and decadal scales.