FISHERY BULLETIN: VOL. 74, NO. 1 



Figure 5. —Distribution of ratios ofp,p'DDD to p,p' DDT. In 

 the shallow nearshore areas the ratios exceed 2:1, while in the 

 deeper waters the ratios are less than 1:1. The higher ratios 

 were probably enhanced by sewer cleaning operations in 

 1970-71. 



The DDT deposits in the deeper waters must 

 have been transported there directly from the 

 sewer outlets before much metabolism could take 

 place. If they had originated from bottom sedi- 

 ments closer to the sewer outfalls and in shal- 

 lower waters, the DDE content would be much 

 higher. DDE averages about 85% of total DDT in 

 biological material in this area; therefore, most of 

 the total DDT in bottom sediments in the deeper 

 water could not have originated from this source. 



For the time series for total DDT accumulation 

 in myctophid fish (MacGregor 1974), DDE was 

 less than DDT from 1949 to 1956, but in the 

 subsequent years DDE became much higher. If 

 the deep water with relatively low DDE had re- 

 sulted from biological fallout as represented by 

 the myctophids for 22 yr (1949-70), and if there 

 had been no metabolism at depth, the DDE would 

 have been twice as high as the DDT rather than 

 one-third as high. 



There is either very little metabolism in deep- 

 water sediments, or there is no metabolism, and 

 the small amounts of DDD and DDE found there 

 are the result of fallout from material metabo- 

 lized in the better-oxygenated surface and inter- 

 mediate depths. 



In commercial DDT, the ratio of p,p' DDT to 

 o,p'DDT is about 4:1 (i.e., o,p' DDT is about 25% 

 ofp,p'DDT). The distribution of these latter val- 

 ues for the sediment samples indicate that 



o,p 'DDT is about what might be expected, while 

 o,p' DDD is higher and o,p' DDE is lower (Table 2). 



In the case of DDT this may mean that o,p ' DDT 

 metabolizes as readily as p,p' DDT. The two high 

 positive correlations with the parameters indicat- 

 ing high metabolism, p,p'DDD/p,p'DDT and 

 p,p'DDE/p,p'DDT, may indicate that o,p' DDT 

 metabolizes more readily than p,p' DDT under 

 conditions of low metabolism of DDT to DDD and 

 DDE. Both the ratios of o,p' DDT to p,p' DDT and 

 o,p ' DDD to p,p ' DDD tend to be high in the bottom 

 sediments north of Santa Catalina Island and in 

 Santa Monica Bay, while ratios tend to be low just 

 south of Palos Verdes Peninsula and in the sandy 

 shallower waters to the east of this area (Figures 

 6, 7). The association of greater distance from the 

 sewer outfalls and lower total DDT values with 

 high ratios is undoubtedly fortuitous, although 

 the few very high ratios are associated with very 

 low DDT values and probably result from poorer 

 resulting measurements and interfering sub- 

 stances that are no longer completely dominated 

 by DDT at these very low values. 



The ratios of o,p' DDE to p,p' DDE are greater 

 than 1.00:1.00 for 19 stations. Unlike the other 

 two ratios these high ratios are associated with 

 depth. They also tend to be concentrated in the 

 deeper waters just off the Palos Verdes shelf 

 where the sewer outfalls are located (Figure 8). 

 These apparent high relative values of o,p' DDE 

 are probably caused by interfering substances, 

 probably DDMU, a metabolite of DDD, which is 

 not being further metabolized under the condi- 

 tions prevailing at these stations. 



Table 2. — Frequency distributions of ortho-para isomer as a 

 percent of para-para isomer of DDT, DDD, and DDE in bottom 

 sediments. 



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