Composition and Distribution of Macrobenthic Invertebrate Fauna 



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GEOGRAPHIC AREA 



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Figure 221 

 Density and biomass of Ophiuroidea in each of the six geographic areas. 



different types were evident. Densities were low 

 (16 to 26 individuals/ nr) in gravel, sand, and shell; 

 intermediate (38 and 58/m 2 ) in till and silt-clay; and 

 high (94/m 2 ) in sand-silt (Table 16; Fig. 223). 



The trend of biomass in relation to sediment 

 type was nearly the same as that revealed by den- 

 sity. Small biomasses of ophinroids occurred in 

 gravel, sand, and shell; intermediate quantities 

 were found in silt-clay; and largest biomasses (5.3 

 and 5.8 g/m 2 ) occurred in till and sand-silt (Table 

 18; Fig. 223). 



Occurrence of ophinroids in the samples re- 

 vealed a pattern similar to those of both density 

 and biomass. They were present in a relatively 

 small proportion (29-40%) of the samples from 

 gravel, shell, and sand, and they were present in a 

 substantially larger share (62-68%) of the samples 

 in till, sand-silt, and silt-clay (Table 20). 



Relation to Water Temperature 



Ophiuroid density, biomass, and frequency of oc- 

 currence all conformed generally to the same 

 trend of high abundance where the temperature 

 range was less than 16°C, and low abundance 



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Figure 222 



Density and biomass of Ophiuroidea in relation to water 

 depth. 



