NO. 2 HARTMAN, BARNARD: BENTHIC FAUNA OF DEEP BASINS 221 



square meter for the Campbell grab. Except for San Pedro, Santa Monica 

 and Santa Catalina Basins, the data are not reliable, due to the small 

 number of samples. However, none of the figures is widely divergent. 

 The shallow basins have about the same standing crop as basins two 

 or three times deeper; but we have previously discussed the low oxygen 

 values for the shallow basins because of the oxygen minimum layer lying 

 at the depth of water supply (see Number 1 ) . 



It would be expected that food supplies to the deeper and seaward 

 basins would be smaller than to shallow basins, so that food might be a 

 limiting factor to standing crop in the deeper basins, while in the shal- 

 lower basins the limitations are in oxygen. We reemphasize the theoreti- 

 cal consequences of this situation, in that shallow basins are provided 

 with larger organic food supplies, which are reworked at a slower rate 

 (discounting bacteria) and thus accumulate and are lost by burial, espe- 

 cially since sedimentation should be faster in the shallow nearshore basins. 

 However, it must be remembered that high plankton productivity 

 occurs over the Santa Rosa-Cortes ridge seaward of the Santa Cruz and 

 San Nicolas Basins, so that some increase in sedimenting organic matter 

 might be expected in adjacent deeper basins, more than if the relationship 

 of distance from shore to food supply were direct. 



ABUNDANCE OF ANIMALS IN THE BASINS 



The frequency of animal specimens on an areal basis is quite low in 

 the basins as compared with the shallow coastal shelf. A uniform calcula- 

 tion of abundance in the basins is impossible, for each basin has not been 

 uniformly sampled in relation to any other. However, the simple average 

 of abundance taken from Table 1 of 71 animals per square meter in the 

 basins is a remarkable contrast to the 3954 animals per square meter for 

 the coastal shelf and upper slope (10 to 200 meters), based on 176 

 samples assessed in the progress of our shelf studies, which are materials 

 as yet unpublished. 



The ratio among various phylogenetic groups shows considerable 

 contrast between basins and shelf, as listed in Table 2. On the shelf, 

 crustaceans and polychaetes are of equal abundance, whereas in the 

 basins polychaetes are eight times more abundant than crustaceans. 

 Echinoderms are less than half as numerous in the basins but mollusks 

 remain of about the same percentages. Because of the high frequency 

 of sipunculids in San Nicolas Basin, the sipunculid percentage is greatly 

 increased in the basins; but Table 2 shows the percentage recalculated 



