changed from degraded or undegraded to marginal (or vice versa) from the first visit to the second visit, no 

 sites fell within quadrants 1 and 3, indicating that no sites were inversely classified as degraded or undegraded. 

 Correlation between the benthic index from the temporal replicates was significant (p <0.05; r = 0.83). The 

 Kappa statistic (k) was used to test the degree of agreement in classification by the benthic index between 

 site visits. The null hypothesis of no agreement (H^: k =0) was rejected at a = 0.5. The Kappa statistic (k = 

 .644) indicated moderate agreement in the classification between visits. This validation of the benthic index 

 was determined to be successful in showing minimal within-year temporal variability. 



10 



9 



8 



7 



6 



5 



4 



3 



2 



1 





 -1 

 -2 

 -3 

 -4 

 -5 



-5-4-3-2-1 1 2 3 4 5 6 7 8 9 10 



Benthic Index - Site Visit 1 



CM 



> 

 <u 



CO 



■ 



X 



& 



Figure 3-4. Comparison of benthic index values from replicate visits within a sampling season 



to a site. Quadrant 2 indicates sites classified as undegraded for both visits; quadrant 4 

 indicates sites classified as degraded for both visits; quadrants 1 and 3 indicate sites that 

 were classified differently for both visits. Sites that fall within the gray shaded area 

 (except for those sites in the center of the cross) changed classification from degraded or 

 undegraded to marginal (or vice versa) from visit 1 to visit 2. 



Guideline 10: Temporal Variability - Across Years 



Indicator responses may change over time, even when ecological condition remains relatively stable. 

 Observed changes in this case may be attributable to weather, succession, population cycles or other 

 natural inter-annual variations. Estimates of variability across years should be examined to ensure that 

 the indicator reflects true trends in ecological condition for characteristics that are relevant to the 

 assessment question. To determine inter-annual stability of an indicator, monitoring must proceed for 

 several years at sites known to have remained in the same ecological condition. 



3-17 



