CHEMICAL ALTERATIONS 



Stressor 



Disturbance 



Metric Response 



PHYSICAL HABITAT ALTERATIONS 



Stressor 



Disturbance 



Metric Response 



ll 4' Finily.Spccici Richaaii 



i ^ ■ Trophic SmUjia 



4' « Rtprodacuvc Smic|i>t 



f> TolaraalSpai 



HYDROLOGIC ALTERATIONS 



Stressor 



Disturbance 



Altered Pood Rcm 

 (Beolhoi, Aliae) 



Metric Response 



4' Family, Spccici Richnen 



4> f Reproductive Smiciwa 



I ^ Tolciaoi Spawoi 



BIOLOGICAL ALTERATIONS 



Stressor Disturbance 



Metric Response 



Figure 4-2. Conceptual model of indicator, showing linkages between various types 



and classes of stressors and component metrics [Derived from Karr (1985), 

 Fausch ef a/. (1990), and U.S. EPA (1997)]. 



4-9 



