Diatom spatial variations in Gull Lake (California) sediments: implications for improving paleolimnological interpretations in small glacial lakes

Diatoms have been extensively used as paleolimnological indicators because they acutely respond to changes in their environment. Diatom assemblages recovered from sediment cores are a mixture of benthic and planktic assemblages that may have been transported away from their source environment or deposited near their habitat. Thus, there is an inherent variability in the diatom deposition across the sediments of a lake. With the aim of characterizing this variability and identifying how it may affect palaeoecological reconstructions, we identified diatom communities and assemblages from a series of sediment cores, surface sediment samples, and samples from different lake microenvironments (submerged macrophytes, sediments, marsh, meadow and attached algae). Comparing the sediment cores, we found differences in the timing of diatom assemblage shifts, which we attribute to differences in the diatom distribution in the sediments. Additionally, we identified gradients of diatom deposition where benthic and tychoplanktic diatoms dominate assemblages near shorelines and planktic assemblages dominate toward the lake center. We attribute benthic and tychoplanktic distribution to distance to the source and recognize that diatoms associated with modern microenvironments are underrepresented in the sediments because of their attachment to a substrate.