SHEDDING SOME LIGHT INTO CRYSTAL LAKES: HOW DIATOMS CAN INDICATE CHANGE

Crystal Lakes is a system of four kettle lakes located in Medway, Ohio (39° N 53', 84° W 01'). The lakes are surrounded by residential housing and line up in a north to south direction. Most of the biggest lake (Main Lake) is shallow because a large carbonate shelf covers most of the bottom of the lake except for a gap near the southern shore, where the water is 11 meters deep. In 2007, Thomas Lowell and colleagues retrieved a sediment core from the deep part of main lake. The core consists of 9 meters of clay, with gravel, presumably of glacial origin, at the base.

Fossil diatoms, photosynthetic algae with glass shells, which can be identified to species, are preserved in the sediments. The ratio of raphid (benthic) diatoms to araphid and centric (usually planktonic) diatoms fluctuates over time, possibly indicating changes in lake depth. In order to determine the relationship between diatom assemblages and water depth, we are analyzing diatom assemblages from different modern habitats within Main Lake, including water-column samples from the end of a dock (water depth ~ 1 m) and from sediment at the edge of the lake (water depth ~ 30 cm) and from the shallow channels (water depth ~ 10-30 cm) that connect the lakes. If water levels drop and the shallower parts of the lake go dry, the value of the homes around the Crystal Lakes will go down, so it is in the interest of the community to estimate how sensitive the lakes’ water levels are to climate change.