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| A multi agency project funded by US EPA's STAR Program | ||||||||
Collecting Diatom Samples
Collection of undisturbed diatom samples from fairly soft sediments (sand, silt, mud, clay) is done using a coring device. The core tube is carefully pushed straight down into an undisturbed area of the lake bottom; suction holds the sediment in place when the core tube is removed from the sediment. Extension handles on the core tube allow sediment cores to be taken in water up to 15 meters (50 feet) deep. Diatoms are collected in deeper waters by lowering coring devices on ropes.
Diatoms in the very top few millimeters of the lake sediment are from diatom communities present this year and in the very recent past. Diatoms buried deeper in the sediments represent communities present in the past.
Coring devices don't work well in areas with rocks, wood or plant debris. In these areas, diatom samples are collected by scraping the surfaces of rocks and wood (the slimy layer that builds up on rocks and other items in the water contains many diatoms).
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