The objective of this study was to evaluate the effect of agricultural pollution on periphyton in streams and rivers of southern Que´bec. influence the strength of the temporal variation. Some data did not respect normality after be- ing transformed. However, as noted by Scheffe´ (1959) and Montgomery (2001), ANOVAs are relatively in- sensitive to moderate deviations from normality and Land use analyses Mean values for the physico-chemical variables at each site are shown in Table 2 and land use information is shown in Table 3. Conductivity, TN, NH+-N, NO−- 4 3 this deviation is unlikely to affect the major effects ob- served here. Previous studies.
