Sedimentary Diatoms and Chrysophytes as Indicators of Lakewater Quality in North America

Water resources are being increasingly affected by anthropogenic activities. However, long-term data are required to track shifts in environmental variables and to characterize the trajectories of aquatic ecosystems accurately. Unfortunately, historical water quality data are often lacking, and so environmental monitoring programs must either continue for many years before meaningful trends can be inferred or else indirect proxy techniques, such as paleolim nological approaches (Smol, 1992; Charles et al., 1994; Anderson and Battar- bee, 1994), must be used. This chapter summarizes some of the ways that we have used diatom and chrysophyte paleoindicators to assess changes in water quality in North American lakes.