Composition and Distribution of Macrobenthic Invertebrate Fauna 



187 



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Figure 201 

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



Holothuroidea — Holothurians formed a moderate com- 

 ponent of the New England benthos in terms of bio- 

 mass, but made up only a minor portion of the total 

 number of specimens (Table 3). This was due mainly to 

 the relatively large size of individual specimens. Mem- 

 bers of this group averaged 3 g each, which is a size 

 unsurpassed by any other major faunal group collected 

 in this study. The larger specimens, Cucumaria and 

 Molpadia, were 10 to 14 cm long, and 2 to 4 cm in 

 diameter. The smallest specimens were juvenile Psolus 

 about 4 mm in length. 



Five orders of holothurians were represented in the 

 samples (Table 4). The dominant group, from the stand- 

 point of abundance and taxonomic diversity, was the 

 Dendrochirotida. Few species and specimens were taken 

 belonging to the orders Molpadiida, Apodida, 

 Aspidochirotida, and Dactylochirotida. 



Color of specimens in this region was generally uni- 

 form over the body surface (except for the contrasting 

 light colored tube feet in some species), which usually 



was reddish-brown, tan, or occasionally light cream. 

 One small species was very dark violet and black. 



Holothurians occurred in 202 samples (19% of to- 

 tal). Their density averaged 4.3/m L ' and their biomass 

 averaged 12.9 g/m 2 (Table 5). 



Geographic Distribution 



Holothurians were prevalent over large sections of the 

 Gulf of Maine and in the offshore Southern New England 

 Shell area (Fig. 208). They occurred on Georges Bank in 

 low densities and in very few samples. Relatively high 

 densities (25 to 88 individuals/m 2 ) occurred over rather 

 large portions of the central Gulf of Maine and along the 

 southern end of Great South Channel. In most localities, 

 however, the average densities were less than 9 dividuals/ 

 irr. In terms of biomass, holothurians were present in 

 substantial quantities, usually greater than 1 g/m 2 , and 

 not uncommonly in quantities of 10 to over 50 g/m'-. 



Among the six standard geographic areas, holothuri- 

 ans were present in largest quantities in the Gulf of 



