Composition and Distribution of Macrobenthic Invertebrate Fauna 



37 



EXPLANATION 



MEAN WEIGHT OF ANIMALS 

 ,d Y PER SQUARE METER OF BOTTOM 

 ALL TAXA COMBINED. 



Figure 14 



Quantitative composition of the total macrobenthic- invertebrate fauna in 

 relation to the six standard geographic subareas. A. — Mean wet weight of 

 animals per square meter of bottom area; B. — Percentage composition, by 

 biomass, of the major taxonomic groups. 



A gradient was evident in the density distribution. In 

 the three shallow water areas — Nova Scotia, Georges 

 Bank, and Southern New England Shelf — average den- 

 sity increased in the order listed from the northeast to 

 the southwest. The Southern New England Shelf area 

 (2,382/m 2 ) had about twice the density of the Nova 



Scotian area (1,163/m 2 ). The Gulf of Maine averaged 

 839/m 2 , and the two slope areas had average densities 

 of about 300/m 2 . 



Biomass distribution followed precisely the same rank 

 order as density, and the magnitudes of differences in 

 biomass from one area to another were roughly the 



