106 



NOAA Technical Report NMFS 140 



strates to high quantities (0.81 and 0.89 g/ 

 m 2 ) in sand and sand-silt. 



Specimens from the shell substrates were 

 the smallest in individual size. 



Frequency of occurrence of sipunculids 

 in the samples was moderately low and 

 approximately equal among the different 

 types of bottom sediments (Table 20). 

 Range in percentage occurrence was 17 to 

 28, with highest values in sand and sand- 

 silt; lowest values occurred in shell and silt- 

 clay sediments. 



Relation to Water Temperature 

 Sipunculid density, biomass, and frequency 

 of occurrence generally tended to decrease 

 as the range in temperature broadened 

 (Fig. 85). None were found where the tem- 

 perature range exceeded 20°C. 



Density averaged about 5 to 9 individu- 

 als/m J where the temperature range was 

 restricted and diminished to zero where 

 the temperature range was most extensive 

 (Table 21). The percentage of the total 

 benthic fauna made up of sipunculids de- 

 creased at a rather uniform rate as the 

 temperature range increased (Table 22). 



Biomass of sipunculids was low or mod- 

 erately low, and the changes in quantity in 

 relation to temperature range followed pre- 

 cisely the same pattern as those in relation 

 to density (Tables 23. 24). Biomass aver- 

 aged about 0.7 to 1 g/m 2 in the narrow 

 temperature range classes and decreased 

 to zero where the temperature range was 

 greater than 20°C. The percentage bio- 

 mass composed of sipunculids also decreased 

 as the temperature range expanded. 



Frequency of sipunculids in the samples 

 ranged from to 29% (Table 25). Thev 

 occurred most frequently, 25 to 29'- . in 

 samples where the temperature range was 

 less than 12°C. Where the temperature 

 range was broader than 12°C, the occur- 

 rence of sipunculids dropped substantially 

 and thev were absent in samples from ar- 

 eas where the temperature range was more 

 than 20°C. 



Relation to Sediment Organic Carbon 

 Sipunculids showed a decided preference 

 for sediments with moderately low to low 

 amounts of sediment organic carbon (Fig. 

 Ni>). Both measures of abundance were 

 greatest in the two (lasses between 0.01 



