4.0 RESULTS 



4.1 Relative Toxicity 



There were marked differences in the responses of the five test 

 organisms to sediment porewater from the same sites (Figure 4.1). 

 Luminescence of the marine bacterium, Photobacterium phosphoreum, 

 (Microtox test) was inhibited by 34% at SS313.0 on the Sanitary and Ship 

 Canal and 32% at CS307.4 on the Calumet Sag Channel. Maximum stimula- 

 tion of approximately 50% occurred at the next site upstream on the 

 Calumet Sag Channel, CS318.5. Responses to porewaters from other sites 

 were slight and variable, sometimes mildly inhibitory and sometimes 

 mildly stimulatory. 



Photosynthesis by the freshwater alga, Selenastrum capricornutum, 

 was markedly stimulated, by a factor of nearly 2, by sediment porewaters 

 from the mouth of Swan Lake, IR6.0, and the Sanitary and Ship Canal, 

 SS310.0. Stimulation is an indication of nutrient enrichment; e.g., by 

 nitrogen and phosphorus (Ross et al . 1988). The greatest inhibition, 

 -86%, was caused by sediment porewater from Lake Chautauqua, IR125.5, 

 although inhibition also occurred at IR72.0, IR281.1, SS313.0, SS315.3, 

 and CS307.4. 



A large percentage of the rotifers, Branchionus caTciflorus, died 

 in porewaters from Meredosia Lake (IR72) and Lake Chautauqua (IR125.5), 

 but the rotifers exhibited no significant responses to samples taken 

 anywhere else (Figure 4.1). 



In contrast to the microorganisms (bacterium, alga, and rotifer), 

 the macroinvertebrates C. dubi'a and M. transversum were remarkably 



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