129-63 Tale of Two Centrics: An Analysis of Diatom Paleoecology in Lake Core Records from Silver Lake and Shadow Lake, Sierra Nevada, CA

Abstract:

Diatom assemblages from lake sediment cores can be used as indicators for changing environmental conditions and can be used to study both regional and broader global climate and temperature changes. Shadow and Silver Lakes are both small, hydrologically open glacial lakes located in the eastern Sierra Nevada region of California. Despite these similarities, Shadow Lake is located higher in the mountains, where Silver Lake is located in a more populated region; due to this, these lakes are impacted by different levels of human settlement. This study will examine palaeoecological changes present in two short cores, one from each lake, with sedimentation rate from nearby June Lake suggesting that these cores preserve a record of around the past 200-500 years. Diatom assemblages from these two cores, as well as surface samples from both lakes which are used as a proxy for paleoenvironmental change. Preliminary smear slide investigations show that Silver Lake contains an abundance of fairly well-preserved diatom taxa, while the Shadow Lake diatoms are rarer, less diverse, and are generally more fragmented. Further investigations work with cleaned sediment samples, which are used to compile a voucher flora of taxa present, and diatom valves are counted to determine relative abundance throughout each core. Surface samples from the lake bottom are used to assemble a modern biogeographical profile of the lake, as well as providing a broader perspective on the diatom communities present. Changes in diatom ecology over time are used as a proxy for the influence of Euro-American settlement altering lake state over the course of the past ~200 years, with hypothesized greater changes present in Silver Lake, due to its closer proximity to human infrastructure. This leaves it more vulnerable to the impacts of pollution, eutrophication, and invasive species, which would in turn influence diatom communities present in the lake, with implications for better lake stewardship in the region. Palaeoecological changes shared between these lakes will also be examined to better understand the effects of anthropogenic climate change on this region as a whole.

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