Composition and Distribution of Macrobenthic Invertebrate Fauna 



195 



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GRAVEL TILL 



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SHELL SAND 



SAND- SILT- 



SILT CLAY 



BOTTOM SEDIMENTS 



Figure 211 



50 



— 25 



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— 20 



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Density and biomass of Holothuioidea in relation to bottom sediments. 



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0-3.9 4-79 8-119 12-159 16-19.9 20-239 



ANNUAL RANGE IN BOTTOM WATER TEMPERATURE 



IN DEGREES CELSIUS 



Figure 212 



Density and biomass of Holothuioidea in relation to annual range of 

 bottom water temperature. 



Bank area. Moderately high ( 13 to 33 g/m 2 ) biomasses 

 of echinoids were found off Nova Scotia, in the Gulf of 

 Maine, and on the Southern New England Shelf. Low- 

 est biomass averages occurred in the slope areas (Table 

 8; Fig. 215). 



Echinoids were present in only moderate to small 

 percentages of the total number of samples. Frequency 

 of occurrence was moderate (19 to 51%) in the four 



continental shelf areas, and low (8 to 9%) in the two 

 slope areas (Table 10). 



Bathymetric Distribution 



Echinoids occurred in water depths ranging from 7 to 

 2,950 m. Average densities were highest (127 individu- 

 als/m 2 ) near mid-shelf depths (25 to 49 m) and dimin- 

 ished in both shallower and deeper regions (Table 1 1; 



