lOjDOOi 



7,500 



e 



CO 



_l 

 <t 



Q 



> 



Q 



— 2,500 



5,000 



9m 



I « 1 1 



I   



  I 

 I   



 • I 



   



   



  I 



R  • 



 • I 



n=IO 



O «0 lO »0 O m 



•« fO (VJ -r T V 



I I I  I ' 



lO lO i O «o o 



to (VJ — "" 



18m 





FISHERY BULLETIN: VOL. 78. NO. 2 



E3 Dendrasterexcentricus 

  Crustacea 

 Hn Mollusca 

 □ Vermes 



DEPTH (cm) 



30m 



ioi 



Figure 5. — Mean number of individuals per square meter per long core layer in n long cores in Monterey Bay, Calif. Vermes are 90% 

 polychaetes and include enteropneusts, phoronids, oligochaetes, and nemerteans. 



30 ID 



Q Rare taxo 



9m 



Molpodto sp 



o O o o 



« lO - V 



I I ' I 



o o o o 



ro CVJ <^ 



Amphfuro 

 ocrystota 



18 m 



O O o o 

 lO l»l T V 



DEPTH (cm) 



Figure 6. — Mean biomass of animals per suction dredge layer in 

 Monterey Bay, Calif, (except at 30 m, where n = 1). Rare taxa 

 indicated. See Figure 5 for bar legend. 



442 



Sediment movements in the canyon head in- 

 cluded unidirectional dowoi-canyon creeping and 

 slumping as well as oscillatory movements. Diver 

 observations and measurements at permanent 

 bottom stations indicated a general shoaling of 

 shallow (5-15 m) terrace walls and an accumula- 

 tion of drift plants (primarily Ulva lobata, Macro- 

 cystis pyrifera, Zostera marina) during the sum- 

 mer and early fall. Slumping of terrace walls and 

 down-canyon flushing of channels were coincident 

 with the first fall storms and continued through 

 the winter (see Arnal et al. 1973). The same sea- 

 sonal cycle of sediment accumulation and flushing 

 was observed at the heads of the Scripps and La 

 Jolla Submarine Canyons (Shepard and Dill 

 1966). 



One of the major slumping events occurred at 

 the shoreward end of the flat canyon ridge. Sedi- 

 ment creeped down the terrace wall (5-14 m), 

 across the ridge ( 14 m), and into the deeper canyon 

 channel (25 m). The slumping was evidenced by a 

 change in the position of the terrace wall, the 

 exposure of consolidated mud outcrops on the ter- 



