Table 32 continued. 



a Sediment Quality Guidelines from U.S. EPA (1993). 

 b Effects Range Median values from Long et al. (1995) 

 c Effects Range Median values from Long and Morgan (1990) 

 d Sediment Quality Criteria from U.S. EPA (1994) 



The relationships between amphipod toxicity and the concentrations of a number of toxic chemicals in 

 the samples are plotted in the following graphs (Figures 37-45). In addition, each graph includes the 

 Spearman-rank correlation coefficient for that particular chemical and the respective sediment quality 

 guideline value. 



Amphipod survival decreased steadily with increasing concentrations of p,p'-DDE in the samples (Figure 

 37). In the two samples with very high amphipod survival, the concentrations of p,p'-DDE were very 

 low (<10 ng/g). In the sample that caused zero amphipod survival, the concentration of p,p'-DDE was 

 the highest among the 20 samples (>70 ng/g). In most of the samples in which p,p'-DDE concentra- 

 tions were less than the ERM value (27 ng/g, Long et al., 1995), amphipod survival was relatively high 

 (>70% in all but one sample). In contrast, amphipod survival was relatively low (<70%) in all but one 

 sample in which the concentrations of p,p'-DDE exceeded the ERM value. However, MacDonald 

 (1994) estimated a Sediment Effect Concentration (SEC) of 6.58 mg/kg dry wt. (6580 ng/g) for the 

 sum of DDEs, two orders of magnitude greater than the highest concentrations observed in the Phase 2 

 samples. Based upon a database compiled from studies focused upon the effects of the DDTs, the SEC 

 of MacDonald (1994) probably is more reliable than the ERM of Long et al. (1995). Therefore, al- 

 though amphipod survival was strongly correlated with the concentrations of p,p'-DDE, this com- 

 pound probably contributed minimally to the toxicity since the concentrations were far below a reliable 

 threshold concentration. 



Although the correlation between amphipod survival and the concentrations of the sum of the six DDT 

 isomers was significant (Rho = -0.576, p<0.05), the concentrations of these compounds were relatively 

 low. Total DDT concentrations ranged from 9.5 to 287.4 ng/g (median = 169.0 ng/g), considerably 

 lower than the estimated SEC of 7120 ng/g (MacDonald, 1994). Expressed in units of organic carbon, 

 total DDT concentrations ranged from 0.6 to 12.0 wg/goc (median = 4.4 Mg/goc); again well below the 

 10-day toxicity threshold in laboratory bioassays (300 Mg/goc) and the 10-day LC50 (2500 Mg/goc) in 

 field-collected sediments for the amphipod Eohaustorius estuarius (Swartz et al., 1994). 



There was a very strong relationship between amphipod survival and the concentrations of total PCB 

 congeners, as illustrated by a Spearman-rank correlation of 0.802. The concentrations of total PCBs 



101 



