The first collection was made from each station after an exposure period of 

 three weeks. A second collection was made one week later. 



Analytical Methods 



The mussel tissue is analyzed for metal content by flame Atomic Absorption 

 Spectrometry after wet digestion in concentrated nitric acid. Each sample is 

 oven dried to constant weight, then digested in concentrated nitric acid in a 

 simple reflux system. The digestate is filtered on transfer to 50 ml volumetric 

 flasks, brought up to volume, and analyzed on a Perkin-Elmer Model 603 

 Atomic Absorption Spectrophotometer using Deuterium arc background 

 correction where necessary. The raw data are reduced to ug of metal/gram of 

 tissue, on both a wet and dry weight basis, by computer. 



RESULTS 



Resuhs of analyses for Cd, Pb, Ni, Cu, chromium (Cr), V, and Zn on M. edulis 

 from Stations 2 and 3, as well as from controls, are presented in 

 Figures 3-4 and 3-5 and Table 3-1. 



Except in the case of Pb and V, where the numbers of samples having 

 detectable limits were below the minimum number required for the statistic, 

 the standard deviation is comparable between a sample of 41 or 10 (Table 3-1). 

 This fact establishes that 10 M. edulis are a reasonable sample size with the 

 noted exceptions of Pb and V. After four weeks, Cd levels in M. edulis from 

 mid-Bay, Station 3, were slightly lower than either laboratory-held M. edulis or 



those collected from the polluted area at Station 2. However, the overlap in Cd 

 values between the three sites renders differences insignificant (Figure 3-4). 



Lead, in those four animals from the polluted area having 

 detectable levels, was higher than those levels detected in the laboratory-held 

 animals, and the single animal having detectable levels from Station 3. 

 However, due to the low number of sampling points, statistical significance 

 cannot be estabhshed for these data (Figure 3-4). 



Nickel levels in M. edulis from Station 2 are significantly higher than those 

 measured in laboratory-held animals. M. edulis from Station 3, while not being 

 significantly different from Station 2, or laboratory -held animals, clearly fall in 

 a range midway between those polluted and clean areas. A gradient of Ni, with 

 highest levels in the polluted area of the Bay, diminishing in the mid-Bay, 

 having lowest levels in the lower Bay, is demonstrated by these data. It is of 

 interest to note -that only 19 of the 41 laboratory -held animals had detectable 

 levels of Ni. 



31 



