Paleolimnological investigation of three manipulated lakes from Sudbury,Canada

Stratigraphic changes in diatoms and chrysophytes from three manipulated Sudbury lakes were explored in an attempt to examine the influence of fertilization and/or neutralization on algal microfossil assemblages. Both diatom- and chrysophyte-inferred pH profiles indicate that the pH of Labelle Lake has remained fairly stable in the past. The study of Labelle and Middle lakes indicates that the addition of nutrients to acidic and non-acidic oligotrophic lakes did not directly influence diatom and chrysophyte species composition, perhaps because pH remained stable. The diatom and chrysophyte assemblages of Middle Lake only changed when the pH was raised. In Mountaintop Lake the recent shift in chrysophyte species composition and the resulting inferred pH decline is most likely related to a decline in mid-summer epilimnetic pH. Reliable paleolimnological inferences are difficult in lakes such as these because it is difficult to track limnological conditions in the absence of modern analogues.