Hogchokers exposed for 5 days to 1.24 g 1"-^ of fuller's earth increased 

 red blood cell counts from 1.58 to 2.08 cells X 10^ mrn"^ (millions of 

 cells per cubic millimeter) and increased microhematocrit from 15.62 to 

 19.93 percent (Table 2). The red cell count increase for hogchokers was 

 proportionately the same as the increase in microhematocrit (30.4 and 27.6 

 percent, respectively); for white perch the proportional increase in red 

 cells was much greater than the increase in microhematocrit and hemoglobin 

 concentration. 



Striped killifish were exposed to 0.96 g l"-"- fuller's earth for 5 days 

 (Table 3). Their microhematocrit value rose from 24.99 to 32.29 percent 

 (probability (p) < 0.01), a relative increase of 29.7 percent for the 

 experimental group over the control group. 



Experiments with white perch, striped killifish, and hogchokers demon- 

 strated that significant hematological changes occur after exposure to 

 sublethal concentrations of fuller's earth. Although these species show 

 similar responses to sublethal concentrations of suspended solids, they 

 differ markedly in response to lethal concentrations of the same material 

 (O'Connor, Neumann, and Sherk, 1976). The hogchoker and the striped 

 killifish were difficult to kill. An LC-response curve could not be gen- 

 erated for the hogchoker, which may be due to hogchokers' high tolerance 

 for suspended solids. The killifish showed a high 24-hour LC50 of 38.18 

 g 1"-^ fuller's earth, about the same as the mummichog value of 39 g 1"-^ 

 fuller's earth. However, white perch were classified as a sensitive 

 species because their 24-hour LC5Q values were below 10 g 1"-^ fuller's 

 earth (O'Connor, Neumann, and Sherk, 1976). Low concentrations of sus- 

 pended solids may induce sublethal effects, such as hematological altera- 

 tion, even in relatively tolerant species. The highly sediment-tolerant 

 hogchoker showed a significant increase in energy utilization during a 

 5-day exposure to 1.24 g 1"-^ fuller's earth (see Section IV). 



Sublethal hematological effects of 1.6 g 1"^ fuller's earth suspensions 

 were determined for the common mummichog at 4-, 7-, and 12-day intervals 

 (Table 4) . The mean microhematocrit values of experimental fish were sig- 

 nificantly different from those of control fish at each interval. There 

 was an increase in the mean value of the experimental group at 12 days. 



Spot were studied after a 5-day exposure to 1.27 g 1"-^ fuller's earth, 

 a concentration below the 24-hour LC20 value of 13 g 1"-^ (O'Connor, 

 Neumann, and Sherk, 1976) . There were no significant differences between 

 the hematological values from experimental and control groups (Table 5) . 



The data for striped bass were not directly comparable to data for 

 other species because the bass were exposed for 11 and 14 days (Tables 6 

 and 7). After 11 days' exposure to 0.60 g 1"-^ fuller's earth, there were 

 no detectable differences in red blood cell count, microhematocrit, hemo- 

 globin concentration, or osmolality of experimental and control groups. 

 Striped bass exposed to 1.5 g l"-"^ fuller's earth for 14 days showed an 

 increase in microhematocrit (p < 0.01) over control fish. However, these 



12 



