series of tests of extended duration at low levels of hydrogen sulfide were 

 run on the test species (Table 3). An unfavorable response was assumed to 

 occur when growth, survival, or reproduction were adversely effected. A 

 "no-effect" concentration was identified when no adverse effect on these 

 parameters was noted. Physiological responses may occur at these concen- 

 trations. In some species stimulation occurred at the lowest levels of 

 treatment and resulted in better long-term performance than that exhibited 

 by the controls. 



Tests were conducted for 45 to 826 days in the various species (Table 

 3). The temperature at which various tests were run varied from 11.8 to 

 24 °C with different species. The "no-effect" concentration varied from a 

 minimum concentration of O.001 mg/1 H 2 S at 24 °C in bluegills, to 0.010 

 mg/1 H2S at 18.6 °C in one goldfish test. Bluegills were the most sensi- 

 tive species. A comparison of trout with the warmwater species is diffi- 

 cult because the former were tested at lower temperatures. The life his- 

 tory stage at which different fish species were first subjected to hydrogen 

 sulfide had varied influence on the final "no-effect" level in the differ- 

 ent species. The concentrations designated as "lowest effect level" were 

 the lowest concentrations of molecular H 2 S which showed a measurable 



TABLE 3. CHRONIC EFFECT OF SUBLETHAL CONCENTRATIONS OF HYDROGEN SULFIDE 

 (MG/L) ON TROUT, BLUEGILL, FATHEAD MINNOW AND GOLDFISH 



1 



Two tests. 



^Reproduction inhibition at 0.002 mg/1 iter. 

 R, reproduction; G, growth; S, survival. 



117 



