98 



NOAA Technical Report NMFS 140 



m 2 . Largest average biomass occurred in the South- 

 ern New England Shelf area (Tables 6, 8). 



The percentage of the total fauna made up by 

 annelids was high in both biomass and number 

 of individuals (Tables 7, 10). On a numerical 

 basis, annelids accounted for 22 to 56% of the 

 total fauna. In terms of biomass, annelids formed 

 between 3 and 23% of the total fauna. In the two 

 deepwater zones, Georges Slope and Southern New 

 England Slope, the percentage of the total biom- 

 ass made up by annelids was 22 and 23%, respec- 

 tively. This is an especially large proportion to be 

 formed by any one faunal group and a much higher 

 proportion than that from the continental shelf 

 areas where the percentages were only 3 to 12. 



Annelid worms were present in an exception- 

 allv large proportion of the samples. In all stan- 

 dard geographic areas, except Georges Bank, 

 they were present in 96 to 99% of the samples. 

 On Georges Bank they were present in 89% of 

 the samples (Table 10). 



Bathymetric Distribution 

 Annelids occurred over the entire depth range 

 in which samples were collected, 3 to 3,975 m. 

 Numerical density and biomass were highest in shallow 

 water and decreased in quantity rather uniformly with 

 increased water depth (Fig. 71 ). Average density in the 

 shallowest depth class was 719 individuals/m 2 . High 

 densities (437 to 159/m 2 ) prevailed across the conti- 

 nental shelf and then diminished rather sharply down 

 the slope and on the continental rise, where the aver- 

 age density was only 9/m 2 (Tables 11, 12). 



The biomass of annelids followed precisely the same 

 quantitative trend in relation to water depth as was 

 exhibited by numerical density. Average biomass was 

 largest (27 g/m 2 ) in the shallowest depth zone. Bio- 

 mass was rather high (15 to 25 g/m 2 ) on the continen- 

 tal shelf and dropped to 5 g/m 2 at midslope and to 0.76 

 g/m 2 on the continental rise (Tables 13, 14). 



Annelids were present in a very high percentage of 

 the samples from all depth classes. Frequency of occur- 

 rence among the eight classes ranged from 93 to 100% 

 (Table 15)/ 



Relation to Sediments 



Annelid worms were not only present in all sediment tvpes 

 sampled but occurred in roughly the same density in eat li 

 of the different sediment types (Tables 16, 17; Fig. 72). 

 Average density from all sediment types ranged from 232 

 to 558 individuals/m 2 . Greatest densities were found in 

 sand and gravel bottoms, lowest densities in silt-clay and till. 

 Biomass, also, was rather evenly distributed among 

 the various sediment types. Values ranged from 1 1 to 26 

 g/m 2 . Highest average biomass occurred in sand-silt 



§600 



? => 



--O NUMBER 

 — • WEIGHT 



2 

 O 



t- 



S m 



o o 



15 I S 



* < 



-3 



10 S" 



10 25 50 100 200 500 1000 2000 4000 



WATER DEPTH IN METERS 



Figure 71 



Density and biomass of Annelida in relation to water depth. 



sediments, and the lowest occurred in till. Intermediate 

 and nearly equal quantities, 15 to 16 g/m 2 , were present 

 in the other four bottom types (gravel, shell, sand, and 

 silt-clay) (Tables 18, 19; Fig. 72). 



Annelid worms were present in all samples from till, 

 shell, and sand-silt sediments; however in 97% of samples 

 in gravel and silt-clay. Although annelids were present 

 in 94% of the samples from sand sediments, this cat- 

 egory of bottom type ranked last in this relationship 

 (Table 20). 



Relation to Water Temperature 



Annelids were present in greatest quantities (Table 21; 

 Fig. 73) where the annual range in bottom water tem- 

 perature was broadest, and densities generally declined 

 as the temperature range decreased. Where the tem- 

 perature range was greater than 20°C, average density 

 of annelids was 1,698 individuals/m 2 . At the other ex- 

 treme, where the temperature range was less than 4°C, 

 average density was 212/m 2 . At intermediate levels of 

 temperature range, density was intermediate, 280 to 568 

 individuals/m . The percentage composition of numbers 

 in this group of organisms in relation to the total fauna in 

 the various temperature-range classes varied from 16 to 

 49% (Table 22). Percentages were highest where tem- 

 perature ranges were extremely high and low. 



Biomass of annelids in relation to range of water tem- 

 perature was similar to that for density. Biomass was large 

 (about 40 g/m 2 ), not only in relative terms but in absolute 

 quantities, in areas where the temperature range was broad 



