Do logging and forest fires influence zooplankton biomass in Canadian Boreal Shield lakes?

Zooplankton biomass was assessed in 20 reference lakes, nine logged-watersh ed lakes, and nine burned-watershed lakes during three summers following wa tershed disturbances by logging or wildfires. Biomass of cladocerans, calan oids, cyclopoids, and rotifers was quantified in the 38 lakes for the first year following disturbances. Limnoplankton biomass in four size fractions was quantified during 3 years following disturbances. One year after distur bances, burned-watershed lakes supported 59% more biomass of the rotifer si ze fraction of limnoplankton (100-200 mum) than reference lakes, while logg ed-watershed lakes supported 43% less of calanoid biomass. Two years after disturbances, differences in limnoplankton biomass between burned-watershed lakes and reference lakes were more pronounced than during the first year, while logged-watershed lakes supported levels of limnoplankton biomass no different from those of reference lakes. Three years after disturbances, no significant variations could be detected among the three groups of lakes f or any of the limnoplankton size fractions. The proportion of watershed are a impacted by logging activities was on average less than half the proporti on impacted by wildfires. Nonetheless, both types of disturbances seemed to have opposite effects on the zooplankton biomass during the first year, an d the effects did not extend beyond 2 years.