In addition to those animals that use the lower strata as a refuge, 

 some are commensals in the tubes and burrows of other organisms. Deep- 

 living commensals must be able to withstand the physical conditions in 

 lower strata, but probably have limited burrowing abilities. They may 

 tolerate a short-term burial, but may be incapable of vertical migration. 

 Prinospio airrifera was commensal in the burrows of Callianassa sp. 

 (Oliver, 1973), and survived burial. 



Several of the species actively burrowed into the lower strata. Some 

 were usually below 10 centimeters (e.g., Notomastus tenuis'), but most 

 species were more common nearer the surface. Larger species or larger 

 individuals of these species were generally found deeper in the sediment 

 (Smith and Howard, 1972; Oliver, 1973); however, there were exceptions. 

 One of these Mediomastus aalifomiensis, a small capitellid polychaete 

 worm, occurred deep in the sediment. 



Low oxygen concentration, low interstitial water content, increased 

 compaction, and high-reducing conditions result from burial, and are 

 characteristic of lower sediment levels. 



The bottom in the second enclosure was buried for only 2 days. Data 

 from the five cores taken inside the enclosure, and cores from the control 

 area are presented in Table 10. 



Table 10. Effect of experimental burial on benthic fauna-^ . 



Fauna 



Buried enclosure 



Control 





(n = 5) 



(n = 7) 



Crustaceans and mollusks 







Nc 



6 



34 



Sc 



4 



11 



St 



9 



29 



Worms 







Nc 



SO 



76 



Sc 



14 



19 



St 



27 



44 



Total fauna 







Nc 



55 



110 



Sc 



17 



30 



St 



36 



73 



^Average number of individuals per 0.018-square meter 

 core (Nc) , average number of species per core (Sc) , 

 and total number of species (St) are given for the 

 enclosure buried May 1973 and for the nearby unburied 

 control area. 



Larger animals were able to withstand the short-term burial better 

 than smaller ones. About 82 percent of the individuals and 69 percent of 



41 



