PARENT SESSION
Oral Session #8: Restoration Ecology: Grasslands, wetlands, aquatic. Presiding: G. Noe.
Monday, August 6, 2001. 8:00 AM to 12:15 PM. Hall of Ideas H.
Recovery of zooplankton communities from acidification in Killarney Park, Ontario, 1972-2000: pH 6 as a recovery goal.
Holt, Carrie1, Yan, Norman1,2, 1 2
ABSTRACT- Acidification of lakes has resulted in severe environmental damage including decreases in species richness and loss of sensitive species. Reductions in SO2 emissions have allowed pH's of some lakes to rise above 6, a threshold of biological damage above which communities are considered "healthy". Nowhere has this rise been more evident than in Killarney Park (Ontario). Temporal trends in zooplankton species richness and composition were examined between 1972-2000 in 46 Killarney lakes to assess the biological recovery in lakes with significant water quality improvements (i.e. pH now >6) compared to 2 groups: (1) lakes which were never acidified, and (2) lakes which are still acidified (pH<6). Recovery was not documented in species richness. Time trends in species richness could not be distinguished among the 3 groups of lakes. However, the community composition of lakes in which pH recovered to pH>6 changed from a "damaged" state to a community type typical of neutral lakes. Some recovery was documented in the acidic lakes (which experienced change in median pH 4.6 to 5.0). Though these lakes did not recover to a state typical of neutral lakes, they experienced greater community change towards recovery than the other 2 groups. These results suggest that: (1) recovery to community types typical of neutral lakes does occur as lakes increase to pH>6, and (2) the recovery process is non-linear, occurring at different rates along the pH gradient.
KEY WORDS: acidification, recovery, zooplankton