Composition and Distribution of Macrobenthic Invertebrate Fauna 



103 



Biomass was low (0.01 to <0.01 g/m' 2 ) in 

 the four organic carbon range classes in 

 which they occurred (Table 28). 



The greatest frequency of occurrence 

 (21%) in samples was in the 0.50 to 0.99% 

 range class, but frequency diminished rap- 

 idly in the higher and lower adjacent classes 

 (Table 30). 



Sipunculida 



Sipunculids, or peanut worms as they are 

 sometimes called, are a taxonomically small 

 group but are found in great abundance in 

 some habitats and have a wide distribution 

 in many parts of the world ocean. Although 

 locally abundant in New England waters, 

 they account for less than 0.5%- of the total 

 benthic fauna in terms of both numerical 

 densitv and biomass (Table 3). 



Peanut worms are elongate and cylindri- 

 cal in shape and characteristically burrow 

 into the bottom sediments where they feed 

 predominandy on detritus. A few species 

 utilize abandoned gastropod shells for per- 

 manent shelter, and one small species was 

 found to inhabit empty foraminifera tests. 



Specimens in our samples ranged in 

 length from about 0.5 to 12 cm. 



Brown, in various shades, was the pre- 

 dominant color exhibited by our specimens; 

 most often they were tan, flesh, or reddish- 

 brown. 



Sipunculids occurred in 249 samples (23%. 

 of total). Their density' averaged 5.9/m , and 

 biomass averaged 0.75 g/m (Table 5). 



s 



o 



i- 



«io 



Z(D 



UJ 



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c5° 

 uj or 

 o. uj 



|3 



2co 



o O NUMBER 



• • WEIGHT 





<-■ '• 



_i_ 



— UJ 



, w cc 

 9 < 



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25 50 100 200 500 1000 2000 4000 



WATER DEPTH IN METERS 



Figure 77 

 Densitv and biomass of Pogonophora in relation to water depth. 



Geograph ic Dis t rib ution 



Sipunculids were widely distributed over 

 the study area (Fig. 81), occurring in low 

 densities over large areas of banks and ba- 

 sins. Densities generally averaged between 

 1 and 49 individuals/m 2 and exceeded 

 these values in only three localities. The 

 maximum density detected was 152 indi- 

 viduals/m 2 . 



Average biomass of sipunculids was mod- 

 erately low, usually 1 g or less per square 

 meter, and with few exceptions was less 

 than 10 g/m'-. 



Among the six standard geographic ar- 

 eas there was rather little difference in av- 

 erage density (Table 6; Fig. 82); the range 

 was about 1 to 9 individuals/m . Slightly 



