Composition and Distribution of Macrobenthic Invertebrate Fauna 



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KRCENT OMANIC CAMOM 



Figure 219 



Density and biomass of Echinoidea in relation to sediment organic carbon. 



occurred on the Southern New England Shelf, and a 

 moderately high density (30/m 2 ) occurred in the Gulf 

 of Maine. In the four remaining areas the density was 

 moderate (14 to 17 individuals/m 2 ) and about equal. 



The biomass of ophiuroids, also, was relatively uniform 

 from one area to another; total range was 0.8 to 5.4 g/m 2 

 (Table 8; Fig. 221). Relatively large biomasses (3.3 and 5.4 

 g/m 2 ) were encountered on the Southern New England 

 Shelf and in the Gulf of Maine. Smallest (0.8 g/m 2 ) 

 biomass was on Georges Slope. Although the average 

 ophiuroid biomass on the Southern New England Slope 

 was 2.6 g/m-, an intermediate quantity, the proportion of 

 the total fauna it made up was 13.5%, a much higher 

 proportion than that for any other area (Table 9). 



Frequency of occurrence of these organisms was mod- 

 erately low (22 to 35%) in the samples from Georges 

 Bank and, surprisingly, on the Southern New England 



Shelf. Ophiuroids were present in 55 to 64% of samples 

 from all other areas (Table 10). 



Bathymetric Distribution 



Ophiuroids were taken at depths ranging from 13 to 

 3,820 m. Their density distribution revealed a pro- 

 nounced zone of high abundance (35 to 87 individu- 

 als/m 2 ) at depths between 50 and 500 m (Fig. 222). 

 Lower densities (0.8 to 6.2/m 2 ) prevailed in both deeper 

 and shallower water. The lowest density occurred in the 

 shallowest depth zone, to 24 m. 



The biomass of ophiuroids was more uniform among 

 the various depth classes than was density; however, the 

 same general trend was clearly evident (Table 13; Fig. 

 222). Biomass was relatively large (2.5 to 7.5 g/m 2 ) at 

 depths between 50 and 500 m, and smaller in both 

 deeper and shallower water. 



