Major climatic influences on Yellowstone region lake ecosystems suggested by synchronous transitions in Late Glacial and early Holocene diatom assemblages

Diatom assemblages that span the late-glacial and early-Holocene period were analyzed from three small lakes in the Greater Yellowstone region. The sites vary in surficial geology, elevation, vegetation, and precipitation seasonality, and these differences provide a tool to evaluate the importance of large-scale climatic change relative to localized catchment proces%s on aquatic ecosystem evolution. All assemblages underwent synchronous shifts in community structure in the intervals of 13.9-13.8, 13.2-13.1, 11.3-11.0 and 8.8-8.7cal ka. The shift at 11.3-11.0cal ka also is evident in other proxy records from these sites, such as pollen and charcoal, which suggests large-scale climatic influences on both aquatic and terrestrial ecosystems. Because the shifts in diatom assemblages are synchronous in lakes with variable geological settings and local precipitation patterns, we infer that large-scale climatic change was the principal driver of aquatic ecosystem evolution in this region during the late-Glacial and early Holocene periods.