Composition and Distribution of Macrobenthic Invertebrate Fauna 



79 



Zoantharians occurred in 265 samples (25% of 

 the total). Their density averaged 22.6/m 2 , and 

 biomass averaged 6.4 g/m 2 (Table 5). 



Geogmph ic Distrib ution 



Zoantharia were widely distributed over most of 

 the marine waters off the northeastern United 

 States (Fig. 45). They were especially common in 

 coastal areas and on the offshore banks. Low and 

 moderately low quantities (1 to 49 individuals, 

 and less than 10 g/m 2 biomass) were most preva- 

 lent. Intermediate and high quantities (50 to 572 

 individuals, and 10 to 1,561 g/m 2 biomass) oc- 

 curred in scattered patches. 



Average numerical density ranged between 3 

 and 8.2 specimens/m 2 for all standard geographic 

 areas except Georges Bank where the density av- 

 eraged 92.5/m 2 (Tables 6, 8; Fig. 46). This unusu- 

 ally high abundance on the bank was due mainly 

 to the presence of large quantities of small Ceriantharia 

 and the moderately common Zoanthidea. 



Biomass of specimens reflected entirely different pat- 

 terns of abundance. Average biomass of Zoantharia 

 within geographic areas was greatest (19.5 g/m 2 ) in 

 Nova Scotia and diminished rather uniformly to the south- 

 west (Tables 8, 9; Fig. 46), terminating with a low quantity 

 of 0.7 g/m 2 in the southern New England Slope area. 



Frequency of occurrence was moderate and fairly 

 consistent among the various areas. The percentage of 

 samples containing Zoantharia ranged between 17 and 

 31%, with the lowest incidence rates in the two slope 

 areas (Table 10). 



Bathymetric Distribution 



Zoantharians occurred at depths from 6 to 2,495 m but 

 were most abundant between 25 and 100 m, where 

 their density averaged from 21 to91/irr (Tables 11, 12; 

 Fig. 47). At other depths their density averaged 0.2 to 

 6.8/m 2 . Only a moderate number (5.6/m 2 ) were present 

 at depths from the shoreline to 24 m. Their density in 

 deeper water progressively diminished from 6.8/m 2 in 

 outer shelf depths to 0.2/m 2 on the continental rise. 



In terms of biomass, the relationship between quan- 

 tity and depth of water was considerably different from 

 that described above for numbers of specimens. At 

 depths of to 100 m the average biomass was moderate 



