mortality and observed, on average, 15 percent lower survival in uncontaminated fine- 

 grained sediments than in uncontaminated coarse-grained sediments. They concluded, 

 however, that particle size is probably just a "super-variable" that is correlated with the 

 actual cause of mortality. The 15 percent effect of grain size, alone, upon survival would not 

 explain the magnitude of the response observed in apparently uncontaminated sediments 

 tested in this evaluation. In conclusion, the test of R. abronius survival was among the most 

 sensitive bioassays and had a relatively wide range in response, a relatively high 

 discriminatory power and intermediate precision; however, survival may be influenced by 

 sedimentological variables and the end-points of reburial and avoidance appear to be 

 relatively insensitive and/or highly variable. 



Ampelisca abdita. As opposed to R. abronius, which is a burrowing species, A. abdita forms 

 mud tubes on the surface of fine-grained sediments. This species is indigenous to the New 

 England area, but also has been introduced to San Francisco Bay where it is very abundant 

 (Hopkins, 1986). The development of the A. abdita toxicity test has not yet progressed as far 

 as that with R. abronius. Initial work with the test animal has indicated that it is not 

 sensitive to uncontaminated fine-grained sediments, that it may be sensitive to coarse- 

 grained sediments, and that it is somewhat less sensitive to contaminated sediments than R. 

 abronius. 



In an evaluation of dredged material from Black Rock Harbor (BRH), Connecticut, 

 Rogerson et ah (1985) observed acute toxicity in only one of ten species that was tested: 

 Ampelisca abdita. They calculated a 96-h LC 50 of about 28 percent BRH material. A 

 maximum of 84.8 percent mortality was observed in 50 percent BRH treatments tested for 96 

 hours. The ability of the test animal to build tubes was also impaired by exposure to all 

 BRH treatments. Variability in test results due to the location of the test animal collection 

 site was observed. In accompanying tests, Scott and Redmond (in press) observed effects of 

 BRH material upon growth rate, egg production, and population growth. They also recorded 

 dose-responsive mortality in chronic 18-, 32-, and 58-day tests. For example, in the 18-day 

 exposures mortality was 9 percent, 98 percent and 100 percent in treatments that were 

 percent BRH/100 percent reference material, 25 percent BRH, and 50 percent BRH, 

 respectively. Recent unpublished tests of sediments from New Bedford Harbor, Connecticut 

 also have shown high toxicity of some samples: Over 90 percent mortality in samples from 

 two sites in the inner harbor in 10-day exposures. In comparison, a maximum of 34 percent 

 mortality was observed among the 15 samples tested in the present study with no dilution. 



In the present evaluation, mortalities in the control sediments exceeded those in some of 

 the test samples and probably resulted in the underestimation of the potential sensitivity of 

 this test. As a result, the end-point of survival was relatively insensitive, indicating a 

 significant difference from controls in only 1 of the 15 samples tested; a sample from the 

 Oakland Inner Harbor that was among the most contaminated. The sensitivity of this test, 

 as determined in the present evaluation, may have been greater if the survival of A. abdita 

 in the controls had been higher. The concentrations of PCBs and many trace metals were 

 generally more than an order of magnitude higher in Black Rock Harbor sediments (Rogerson 

 et al., 1985) than in those from Oakland Inner Harbor. The toxicity test results with Black 

 Rock Harbor samples varied with the sampling location of the source of test organisms. 

 Dose-dependent responses of A. abdita to Black Rock Harbor sediments were corroborated 

 with the positive correlations observed in the present evaluation between toxicity and the 

 concentrations of several classes of organic toxicants. The organism did not indicate 

 sensitivity to fine-grained sediments that apparently were not highly contaminated. In 

 conclusion, the end-point of A. abdita survival was less sensitive and had lower 

 discriminatory power than that with R. abronius, but had relatively higher analytical 

 precision than that with R. abronius, was not highly correlated with sedimentological 

 variables, and was relatively highly correlated with several toxicants. The end-point of 

 avoidance was not sensitive and had low precision and discriminatory power. 



Strongylocentrotus purpuratus. Before the present study, the relative sensitivity of sea 

 urchin sperm and embryos to sediments had not been evaluated. However, toxicity tests 

 with urchin or sand dollar sperm and embryos have been evaluated in bioassays of water- 

 borne chemicals and sewage (Dinnel et al, 1982; Dinnel and Stober, 1987; Nacci et ah, 1986). 



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