Abstract:
Four staircase lakes occupying a single watershed located in
the Algoma District, north of Lake Superior were chosen for this
study. I examined the subfossil diatom assemblage in the top
twenty centimeters of the surface sediments in each of these
four lakes in an attempt to reconstruct their respective past pH
history. From these analyses it was possible to test the
hypothesis that the rate of change of diatom inferred pH was not
significantly different in lakes located one below the other in
a single "staircase" within a single watershed system.
My results indicated that the four Z lakes had been acid for
at least the last century. The water color of the three upper Z
lakes (Z1, Z2 and Z3) was brown (>30 Pt Co units). The bottom
lake (Z4) was the only clear water lake in the system «5 Pt Co
units). This bottom staircase lake had no muskeg development
around its shoreline. The alkaliphilous diatoms in the Z
watershed system were important in determining the diatom
inferred pH of the four Z lakes. The centric diatoms were
extremely rare in the clearwater bottom lake (Z4). The ecology
of the Eupodiscales is perhaps important in the interpretation
of sediment in the more acid environment.
Lake Z4 was the only one that had a progressive as well as a
significant decrease in its downcore diatom inferred pH since
the early 1960's. This lead me to speculate that the humic
substances present in the upper three brown water lakes (Z1, Z2 and Z3) were perhaps Important in buffering them against a
further decrease in water pH even though they were located
within an area which was sensitive to acid precipitation.
