XVI International Botanical Congess

The effects of anthropogenic disturbances on epilithic algae were studied,comparing the species richness, assemblages and crust presence between two disturbed and two undisturbed alvar sites in southern Ontario. The rock and algae crust samples collected at the sites were cultured for three weeks and identified. A nested ANOVA showed that there was no significant difference between the disturbed and undisturbed sites in relation to species richness. However, the total number of species identified were considerably higher than previous accounts of terrestrial algae assemblages. The presence of an algal crust was found to significantly increase both the total species richness (p=0.0) and the number of nitrogen fixing cyanobacteria (p=0.0). Contrary to most previous findings there was no significant difference between the presence of crusts in the sites.