HELP ME, OPAL PHYTOLITHS. YOU'RE MY ONLY HOPE

Sediments recovered from lake cores often present an excellent matrix for the recovery of plant remains. This has enabled researchers to reconstruct past floral regimes, typically through the identification of pollen and/or macroscopic plant remains. However, the vagaries of preservation do not always allow for the survival of these remains. Opal phytoliths present another viable option for environmental reconstruction. Phytoliths are microscopic silicates formed in the tissues of many plants. Phytoliths are extremely durable (outside pH extremes) and can often be identified with useful taxonomic specificity. While phytoliths commonly are employed in archaeology, their use in lacustrine contexts could be greatly expanded.

Phytolith research has been hampered by the issues of multiplicity and redundancy, that plants often make multiple types of phytoliths and that related plants make similar phytoliths. That being said, many plants do make phytoliths that are family, genus or species specific. Furthermore, many plant species make assemblages of phytoliths that are recognizable when taken as a whole. Secure identification requires a strong comparative collection. By extracting phytoliths from modern plant specimens, we have started to construct a (publically available) phytolith database that will enable us to make identifications and construct analog floral communities. Additionally, phytoliths can be difficult to separate from the more abundant diatoms commonly found in lacustrine sediment. Here we present a method to extract phytoliths from lake sediments and comparative samples in order to construct a robust description of past floral communities. Using a combination of chemical baths and microsieves, we have been able to concentrate phytoliths into usable frequencies from small amounts of sediment (5 cc or less). Samples are spiked with a non-siliceous microsphere to facilitate statistical calculations, such as influx rates and ubiquity. This is part of a larger project to examine the history of wild rice (Zizania palustris) in Minnesota lakes. Phytoliths have provided evidence for Zizania in contexts where macrofossils have been absent and pollen has been equivocal.