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The natural benthic assemblages differed with changes in the amount of 

 sediment movement or substrate stability. Many animals characterized the 

 relatively stable submarine ridges but few inhabited the unstable terrace 

 slopes of the submarine canyon in Monterey Bay, California (Monterey Canyon) ; 

 even fewer animals were found in channeled areas. 



Dredging in the channel areas removed 60 percent of the original popula- 

 tion of bottom animals. After 1.5 years, the number of individuals was low 

 but the species diversity and evenness indexes were higher than before dredg- 

 ing. 



Disposal of dredged material near the Monterey Canyon head at Moss 

 Landing, California, removed 60 percent of the individuals. After I'.S years, 

 the number of individuals remained low but the species diversity and evenness 

 indexes were higher than before disposal. Organisms adapted to unstable 

 bottom conditions survive burial better than others. 



The ultimate recovery of a disturbed area depends upon the timing of the 

 action in relation to the reproductive cycles and distributive abilities of 

 the benthic organisms in the area. In Monterey Bay, spring and fall are 

 the most active spawning seasons for many benthic animals; dredging or dump- 

 ing should be avoided during these seasons. 



Underwater disposal of dredged material should be made in unstable bottom 

 areas if possible. 



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