The three factors accounted for over 65 percent of the variance; 

 other factors were not interpretable for biologic effects. None of the 

 .organisms, except those characteristic of the marsh and S. viridis , was 

 associated with the major factors. Thus, their distributions were not 

 dependent on the measured parameters. Other physical and chemical 

 parameters determined both population levels and distributions for 

 these species. 



g. Species Diversity . Species diversity at each site was calcu- 

 lated using a Shannon-Weaver index (see Section 111, 1, g) (Table 55). 

 The total fauna (including meiofauna) was used to compute the diversity 

 index. Diversity ranged from 0.33 to 2.33. The diversities in the 

 May and July samples were significantly higher than those in the 

 October and March samples; diversity was generally higher on the deep- 

 water sites (sites 7 and 8) than on the nearshore sites. 



IV. DISCUSSION 



1 . The Ocean Beach . 



The ocean beach has one distinct faunal coiranunity. This community 

 was located in the swash zone and was dominated by E. talpoida. Pearse, 

 Humm, and IVharton (1942) report that Donax sp. occur in this zone and 

 move up and down the beach with the tidal cycle as does E. talpoida; 

 however, densities of adult Donax were low in the swash zone at the FRF. 



Donax sp. has been observed in large numbers in the swash zone at 

 Virginia Beach, Virginia. This beach presents a reduced stress 

 situation compared to the beach at the FRF because of the gently sloping 

 beach face and milder wave conditions. Donax did not remain in the 

 swash zone at the FRF in winter because of the high storm waves. Since 

 the density of juveniles was high in deep water, Donax probably 

 recolonized the swash zone each spring. 



There were two other strongly integrated communities in the deep 

 water, dominated by S. squamata and P. longimerus , respectively. 

 Significant numbers of these species were also present in the swash 

 zone, but their densities were low compared to the deepwater sites. 



The second community on the ocean beach is the S. squamata 

 community. These deposit-feeding polychaetes are found on all sites 

 but are most abundant on sites 5, 6, 7, and 8. Their density was high 

 on site 5, just seaward of the interface between the outer plane facies 

 and the inner course facies. The third community is the P. longimerus 

 community on site 9. The two communities appear to integrate strongly 

 in the area of site 8. The 5. squamata community represents an inshore 

 community extending over the megaripple area, and the P. longimerus 

 community represents the margin of a large community inhabiting the 

 asymmetric ripple area in the offshore zone. 



84 



