Considerable differences in biomass, total numbers, and species composi- 

 tion, as well as individual species abundance occurred within relatively 

 short distances (10 to 25 miles) from Nantucket Shoals to Great South Chan- 

 nel, as shown in Tables 4-1 and VII-15 (Appendix VII). These differences can 

 be used to define the communities and to pair the stations as follows: 



1 . Stations 4 and 9 - Shoal Community - Nantucket Shoals . These sta- 

 tions are characterized by a shallow (40 meters) , well-mixed physical envi- 

 ronment, extremely turbulent during winter months. Zooplankton numbers are 

 strongly dominated by small calanoid copepods of the genera Pseudocalanus and 

 Paracalanus , with medium-size developmental stages, comprising 73% (Station 

 4) and 50% (Station 9) of their numbers. These have been lumped together and 

 will be referred to as Pseudo-paracalanus . The turbulent nature of this 

 shoal environment is demonstrated by the large number of gammarid amphipods, 

 especially Monoculodes , in the collections. These specimens were apparently 

 lifted into the water column in the vertical turbulence. 



The incidence of contamination at Station 4 (Table 4-2) was quite low 

 for Centropages typicus and Pseudo-paracalanus . A somewhat higher value was 

 recorded for C^. hamatus , of which only 10 specimens were examined. C^. 

 typicus samples along the slick boundary (Station 9) were found to have a 

 relatively high incidence of mandibular and ingested particles. 



2. Stations 5 and 8 - Transitional Community . These stations, taken at 

 about 55 meters, exhibit characteristics of both the shoal and channel com- 

 munities. Numbers again are dominated by Pseudo-paracalanus , especially at 

 Station 8. A larger calanoid, Centropages typicus , appears as a codominant 

 form. Total zooplankton numbers are 5 to 10 times less than those recorded 

 at the adjacent shoal stations. Contamination appears greatest at Station 5, 

 outside the slick. Over 50% of the C^. f inmarchicus and C^. typicus were 

 affected; most contained ingested particles. 



3. Stations 6 and 7 - Channel Community . This is a distinctly differ- 

 ent community, characterized by low biomass, low total numbers, and dominated 

 by larger copepods, C^. f inmarchicus (Station 7), and C^. typicus (Station 6). 

 This assemblage is similar in part to the "Calanus community" of the Gulf of 

 Maine (including Calanus f inmarchicus , Pseudocalanus minutus , Metridia 

 lucens , Sagitta elegans, and Parathemisto ) and unlike the Georges Bank winter 

 community, which Clarke et al. (1943) showed to be Pseudocalanus dominated . 

 Contamination at Station 6 outside the slick is low, while Inside the slick 

 at Station 7 a high number of ingested particles were recorded for C^. typicus 

 and Pseudo-paracalanus . 



Significant contamination was found in copepods in all three communi- 

 ties, and the occurrence was not restricted to the visible slick area (Table 

 4-2), indicating that oil contamination occurred in a major component of the 

 food web. Oil droplets removed from the alimentary tracts of the predominant 

 copepod species, Centropages typicus , were examined for petroleum hydrocarbon 

 content using gas chromatography. The resulting chromotagrams were compared 

 by W. W. Kiihnhold (University of Kiel, FRG) and R. Lapan (EPA) with chroma- 

 tograms of oil from the Avgo Merchant and were found to be similar. 



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