UNRAVELING PAST HYDROCLIMATE DYNAMICS IN GULL LAKE, SIERRA NEVADA, CALIFORNIA. INSIGHTS FROM DIATOM EVOLUTION AND COMMUNITY ASSEMBLAGES

Long-term paleoenvironmental records, which can provide a basis for natural variability, are rare in the Sierra Nevada, California. Understanding hydroclimate in this area has become increasingly important as water availability has been dramatically reduced in the past decades. Yet, paleolimnological reconstructions have been limited to Mono Lake, the biggest lake in this basin. However, the Holocene record for this lake has been altered through volcanic activity. Smaller, more sensitive lakes have the potential for providing high-resolution records for the last ~12,000 yrs. With the aim of discerning the climatic variability that has been registered in the Sierra Nevada during the Holocene, and with the hopes of unraveling the effects of modern climate variability in the basin, we collected a series sediment cores from Gull Lake, located at the western edge of the Great Basin in eastern California, which makes it ideal for assessing long-term changes in precipitation regimes in this area. Through a multiproxy approach, combining diatoms, geochemistry and charcoal records, we hope construct a comprehensive record that reveals the past hydroclimate dynamics on the Sierra Nevada. There is an added value to this record, as it offers the opportunity for studying the evolutionary patterns of a recently described endemic diatom species from June Lake, Stephanodiscus coruscus. Diatom evolution events are rarely observed in sedimentary records, so Gull Lake offers a chance to explore whether environmental or climatic factors played a role in how this diatom evolved. Diatom evolution has been consistently linked to climatic and environmental factors so our aim is to discern the possible conditions that, in this habitat, led to changing June/Gull lakes’ conditions, triggering this rapid adaptation response.