NO. 5 



BARNARD: AMPHIPODA 



\-rOTAL 



STANDING CROP 

 SUBMARINE CANYONS 



1 — I — r 



11 €CHmo-\ 



'-'^'^nI^-- 



I I I 



\00 ZOO 300 400 500 600 700 800 900 1000 1200 /300 1400 too 



Depth in Meters 



Graph 3. Cumulative standing crop in submarine canyons related 

 to depth, data reduced from Hartman (1963). 



(Graph 3), because sufficient samples are grouped into several depth 

 classes so as to ameliorate erratic biomass levels. Most striking and per- 

 haps significant is the sudden drop in biomass between 600 and 700 m 

 that may be related to the oxygen minimum layer which occurs between 

 500 and 700 m in this latitude (Emery, 1960, p. 108). 



The standing crop of the depth classes of 100 - 500 m in the canyons 

 approximates that of the typical levels on the outer sandy-silt (or silty- 

 sand) shelf of southern California (compare Barnard and Hartman, 

 1959, figs. 4-6), in depths of about 60 to 100 m. Echinoderms and echiur- 

 oids represent a larger share of the standing crop in canyons than they 

 do on the outer shelf, this share being taken partly from the polychaetes 

 and especially from the mollusks. 



DENSITY OF ORGANISMS 



Polychaetes dominate the benthos of the inshore continental canyons 

 whereas echinoderms are numerically more abundant in the insular can- 

 yons (Tables 2-3, by summation of values in all depth classes). 'I'he 



