Published online by Cambridge University Press: 21 July 2017
Serious environmental issues, including acid rain, eutrophication, and decreasing water availability, require knowledge of the: 1) baseline conditions (i.e., what were conditions like before human disturbance); 2) natural variability; and 3) time or level of disturbance when the system responded to the environmental change. This type of knowledge can only be obtained from a historical perspective, which is best achieved through actual measurements of environmental variables. Such records, however, rarely extend more than a few decades, which is usually insufficiently long to determine baseline conditions and natural variability. Diatoms, single celled algae characterized by a cell wall composed of opaline silica, preserved in lake sediments are one of the most widely used paleoindicators, and provide robust estimates of lakewater pH, nutrient concentration and lake level change. A variety of approaches have been developed to infer environmental variables using diatom data, and robust inferences of many environmental variables are now possible. Using paleolimnological techniques, fossil diatoms have been used to track pH, nutrients and lake levels. These records have significantly contributed to our understanding of the causes and impacts of lakewater acidification, eutrophication and hydrologic change, and provide a basis for developing effective management strategies.