ECOSYSTEM RESPONSES TO STRESS 



115 



every parameter. A comparison of these numbers led to the rankings 

 in Table 4. The P/R ratio, night respiration, and magnesium 

 input-to-output ratio were the least variable parameters during steady 

 state. Ammonia, nitrate, and chlorophyll a fluctuated most. These 

 reinkings, of course, are partially a function of the specific methods 



TABLE 4 



RANKING OF PARAMETER SENSITIVITIES FOR 



STEADY-STATE VARIABILITY, RESISTANCE TO STRESS, 



AND RECOVERY FROM STRESS* 



*The ranking is based on all treatments from both perturbations in the 

 nutrient— energy subsidy experiment. The median coefficient of variation of 

 steady-state observations, the median relative resistance, and the median 

 resilience for these treatments were compared for each parameter to arrive at 

 a ranking. 



used in this study. The median relative resistance and median relative 

 resilience, similarly calculated for each parameter, were compared. 

 The nitrate, P/R ratio, and phosphorus parameters were most 

 sensitive to stress (i.e., least resistant), and particulate matter, 

 chlorophyll a, and ammonia were least sensitive. Ammonia, chloro- 

 phyll a, and night respiration recovered most slowly, but nitrate, 

 phosphorus, and magnesium returned rapidly to their normal 

 operating ranges. Differences in response of various parameters 

 should be considered during the design of a microcosm experiment. 



