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NOAA Technical Report NMFS 140 



nodermata, Mollusca; 4— 7.9°C: Annelida, Crustacea, 

 Mollusca, Echinodermata; 8-11.9°C: Crustacea, 

 Annelida, Mollusca, Echinodermata; 12-1 5. 9°C: Crus- 

 tacea, Mollusca, Annelida, Echinodermata; 16-19. 9°C: 

 Crustacea, Annelida, Mollusca, Echinodermata; 20- 

 23.9°C: Annelida, Mollusca, Crustacea, Echinodermata. 



The relationship of the dominant taxa hiomasses to 

 annual range of bottom water temperature was similar 

 to that of density in that no definite trends were evi- 

 dent. However, a marked change in dominance rank- 

 ing prevailed, wherein the density dominants (crusta- 

 ceans and annelids) were replaced by echinoderms and 

 mollusks as the leading contributors to biomass in nearly 

 all temperature range regimes. Echinodermata domi- 

 nated biomass in four of the six temperature range 

 classes, including the narrowest and broadest ranges; 

 their mean biomass ranged from 12 to 263 g/m 2 . Mol- 

 lusk biomass, second to that of echinoderms in most 

 temperature ranges, was clearly dominant where tem- 

 perature ranges of 8-11.9°C and 16-19. 9°C prevailed; 

 their mean biomass was 129 g/m 2 in the former and 

 340 g/m 2 in the latter. The contributions of the other 

 two dominant taxa, annelids and especially crustaceans, 

 due to their small size, were clearly subordinate in all 

 temperature regimes. Annelid biomass ranged from 10 

 to 40 g/m 2 , and crustacean biomass from 1 to 25 g/m 2 . 



Rank order of dominance for the major taxa in the 

 six annual temperature range classes in terms of bio- 

 mass was as follows: 0-3. 9°C: Echinodermata, Annelida, 

 Mollusca, Crustacea; 4—7. 9°C: Echinodermata, Mollusca, 

 Annelida, Crustacea; 8-11.9°C: Mollusca, Echinoder- 

 mata, Annelida, Crustacea; 12-1 5. 9°C: Echinodermata, 

 Mollusca, Annelida, Crustacea; 16-1 9. 9°C: Mollusca, 

 Echinodermata, Annelida, Crustacea; 20-23. 9°C: Echi- 

 nodermata, Mollusca, Annelida, Crustacea. 



Relation to Sediment Organic Carbon 



As mentioned above (see section "Total Macrobenthos") 

 there was no clear-cut correlation between sediment 

 organic carbon content and fannal abundance except 

 in a few exceptional cases (Tables 26, 28; Fig. 26). 



The numerical abundance of the dominant taxa var- 

 ied widely in relation to organic carbon content for all 

 except Echinodermata. This taxon ranked fourth in all 

 organic carbon content classes except two (0.00% and 

 1.00-1.49%) where it ranked third, slightly ahead of 

 Crustacea. Density of echinoderms was moderately low, 

 ranging from only 3-91 individuals per m . Crustacean 

 density varied widely among the various carbon content 

 classes, ranging from 21 to 1,357/ m 2 . Greatest abun- 

 dances occurred in carbon content levels of 0.01-0.49% 

 (1,066/m 2 ) and 3.00-4.99%, (1,357/m 2 ), with moder- 

 ately low to fairly high densities occurring in carbon 



content levels between these two. Lowest densities (21- 

 22/m 2 ) prevailed in areas where no measurable carbon 

 existed as well as in areas where the greatest amounts of 

 carbon were measured. Mollusca, was one exception, show- 

 ing a positive correlation of generally increasing density 

 with increasing carbon, ranging from 69/ m 2 in areas 

 devoid of carbon to 1,120/m where carbon was between 

 3.0% and 4.9%. No mollusks occurred where carbon 

 content exceeded 5%. Annelida were present in all or- 

 ganic carbon content classes. Their density was signifi- 

 cantly lower at both extremes of the carbon content spec- 

 trum (between 11/m 2 and 81/m 2 ) compared with their 

 abundance (196-504/ m 2 ) in areas containing low (0.01- 

 0.49%) to moderate (2.0-2.99%) amounts of carbon. 



Rank order of the numerical abundance of the domi- 

 nant taxa with regard to organic carbon content was as 

 follows: 0%: Mollusca, Annelida, Echinodermata, Crus- 

 tacea; 0.01-0.49%: Crustacea, Annelida, Mollusca, Echi- 

 nodermata; 0.50-0.99%: Annelida, Crustacea, Mollusca; 

 Echinodermata; 1.00—1.49%: Mollusca, Annelida, Echi- 

 nodermata, Crustacea; 1.50-1.99%: Mollusca, Annelida, 

 Crustacea, Echinodermata; 2.00-2.99%: Crustacea, 

 Mollusca, Annelida, Echinodermata; 3.00-4.99%: Crus- 

 tacea, Mollusca, Annelida, Echinodermata; 5.00%+: 

 Crustacea, Annelida; no Mollusca or Echinodermata 

 were found in this class. 



Similar to numerical abundance, biomasses of domi- 

 nant taxa showed no clear-cut correlation to the or- 

 ganic carbon content of the bottom sediments. Most 

 notable was the considerable echinoderm biomass in 

 all but the highest carbon content classes, compared 

 with its low numerical density. Highest mean biomasses 

 (105 g/m 2 and 562 g/m 2 ) occurred in areas with mod- 

 erately high carbon contents (between 2% and 4.99%), 

 and lowest (6 g/m 2 ) occurred in areas devoid of mea- 

 surable organic carbon. Moderate biomasses, ranging 

 from 23 to 44 g/m 2 , occurred in areas with low to 

 intermediate carbon content levels (0.01-1.99%). Mol- 

 lusca, also absent where the highest measures of or- 

 ganic carbon occurred, nevertheless showed a prefer- 

 ence for some organic carbon content, with highest 

 biomasses (812 g/m 2 and 227 g/m 2 ) occurring in the 

 two carbon content classes between 2.0 and 4.99%. 

 However, moderately high biomass (132 g/m 2 ) was also 

 found where carbon levels were only between 0.01 and 

 0.49%. Lowest biomass (only 0.8 g/m 2 ) occurred in 

 sediments devoid of carbon. Moderate levels of biom- 

 ass (25-13 g/m 2 ) occurred in organic carbon levels 

 that ranged from 0.50 to 1.99%. The mean biomass of 

 Annelida was fairly consistent at moderate levels rang- 

 ing between 1 1 g/m 2 and 27 g/m 2 in areas of organic 

 carbon content ranging between 0.01 and 4.99%,. Low- 

 est mean biomass of annelids (0.11 g/m 2 ) occurred in 

 the highest carbon content class (5+%) and intermedi- 

 ate amounts (7 g/m 2 ) were found where measurable 



