RESPONSE OF PHYTOPLANKTON IN ACIDIC LAKES IN ONTARIO TO WHOLE-LAKE NEUTRALIZATION

Changes in phytoplankton community composition were examined in the acidic Bowland and Trout Lakes to determine whether neutralization (and subsequent stocking with lake trout Salvelinus namaycush in the cases of Bowland Lake) would reverse acidic characteristics. Analysis of community percentage similarity showed that year-to-year variability in phytoplankton community structure would have been low in the absence of neutralization. While changes in phytoplankton biovolumes or chlorophyll a concentrations after neutralization were not significant, there were several taxonomic changes: 1) the shift in the Bowland Lake phytoplankton community away from dominance by the cyanophyte, Rhabdoderma, and 2) the dominance of the prymnesiophyte Chrysochromulina breviturrita in the Bowland Lake phytoplankton community in 1985, 2 yr after neutralization. Results suggest that structural changes (taxonomic) maintained stability of the phytoplankton communities under chemical stress (in terms of standing crop). (See also 90L/08129, 08193 and 08194). -from Authors