the species of crustaceans and mollusks were killed by the burial (Table 

 10). Percentages are based on a comparison of sample from the enclosure 

 and control stations. Survivors in these groups were all larger individ- 

 uals. 



Worm mortalities were again low. About 34 percent of the number of 

 individuals and 39 percent of the species were killed [Table 10). Most 

 of the larger worms lived after burial; mortality was higher for smaller 

 species and individuals. Very few juveniles of polychaete worm, Magelona 

 saoculata, and no specimens of the polychaete, A. oacidentalis , were pre- 

 sent in the enclosed area, yet they were common outside. 



Two polychaete worms, M. calif ovn-iensis and P. airrifeva, survived 

 the burial and their numbers remained similar to those of the control 

 stations. They also tolerated burial in the first experiment (Table 9), 

 and were common below 10 centimeters in the sediment. 



In both experiments, members of the worm fauna (primarily polychaetes) 

 were least affected by burial. Survival was highest in the active bur- 

 rowers, and especially those active burrowers common in lower sediment 

 strata. Small species and individuals of larger species were generally 

 less tolerant of burial. The only exceptions were inhabitants of the 

 lower strata. Surface-dwelling crustaceans and mollusks were most af- 

 fected by the deposition; all died in the first experiment. 



Capability to withstand burial can be predicted by animals' morphology, 

 behavior, usual vertical distribution in the sediment, and stability of 

 the substrate inhabited. These experiments present new information and 

 agree with the review presented by Sailia, Pratt, and Polgar (1972). 



At the disposal site (canyon head) , the fauna is adapted to a larger 

 amount of seasonal sediment movement. The dominant animals were active 

 deposit-feeding polychaetes that apparently restricted the presence of 

 small crustaceans and mollusks. The disposal caused a 60-percent reduc- 

 tion in the number of individuals and an 8-percent reduction in the number 

 of species. On the stable flat bottom, 50 percent of the individuals and 

 66 percent of the species were killed by the first experimental burial. 

 The two locations were subjected to different types of deposition, but 

 the data are still comparable. Canyon fauna is much better adapted to the 

 effects of mass accumulation of sediments. Investigations have involved 

 only the shallow canyon head, and do not necessarily apply to deepwater 

 assemblages . 



3. The Effect of Disposal on the Benthos . 



The effect of dumping dredged materials on the benthos was reported by 

 O'Neal and Sceva (1971) and Sherk (1971). Sailia, Pratt, and Polgar (1972) 

 reviewed the most pertinent studies. Where disposal did create a contin- 

 uous stress and the toxic content was low, recovery of the benthos was 

 completed within 1 to 3 years (Virginia Institute of Marine Science, 1967; 

 Harville, et al., 1967; Pfitzenmeyer, 1970; Sailia, Pratt, and Polgar, 

 1972). 



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