KINNER and MAURER: POLYCHAETOUS ANNELIDS OF DELAWARE BAY 



bottoms. The highest density of H. extenuata in 

 our studies always occurred in the epifaunal- 

 infaunal assemblages, mentioned above. Other 

 species that were present in significant numbers 

 in area H, and also important in the bay but not 

 normally found in offshore assemblages, include: 

 Polydora ligni, P. socialis, Asabellides oculata, 

 Nereis succinea, and Sabellaria vulgaris. 



A number of species, including Glycinde sol- 

 itaria, Spio setosa, and Diopatra cuprea, occurred 

 in areas G and I, but not farther offshore. Glycinde 

 solitaria was found primarily in muddy sands, 

 both in the bay and nearshore areas, which agrees 

 with the findings of Pettibone 1 1963a). The lack of 

 mud on the inner shelf may be the primary reason 

 why they were not found at the offshore sites. 

 Diopatra cuprea and S. setosa were found exten- 

 sively on the intertidal sand flats of Cape Henlo- 

 pen. Only a few individuals of D. cuprea were 

 found in lower Delaware Bay and in areas G and I. 

 Spio setosa was most prevalent subtidally in the 

 epifaunal-infaunal assemblages. 



In addition to estuarine species, members of the 

 offshore assemblages were found in areas G and I. 

 Lumbrinerides acuta (an offshore dominant) and 

 L. fragilis were present in sand stations in both 

 areas. Spiophane bombyx, which was found occa- 

 sionally in sandy sediment in the bay, was an 

 important species in the nearshore marine areas 

 and a dominant in offshore assemblages. The in- 

 crease in density of S. bombyx seaward appears to 

 be a response to increased areas of fine sand, 

 rather than salinity, as S. bombyx was found in 

 estuarine waters of 15%o. 



Midcontinental Shelf Fauna (J) 



Polychaetes represented 35.7% of the total indi- 

 viduals in samples collected in May and 54. 49^ in 

 November, making them the dominant (by 

 number of individuals) benthic group offshore 

 (Maurer et al. 1976). In May, Goniadella gracilis 

 and Lumbrinerides acuta were codominants among 

 all benthic organisms. Clymenella spp. and 

 Aricidea catherinae were also abundant. In 

 November there was a shift in dominance, with 

 the exception of G. gracilis, when Exogone veru- 

 gera and Spiophanes bombyx were established as 

 dominant forms. Parapionosyllis longicirrata was 

 present in a few samples in large numbers, but 

 was not as widely distributed as the other domi- 

 nant species. The following March, Aglaophamus 



circinata became the dominant species based on 

 the large number of juveniles collected. 

 Spiophanes bombyx was the second-most impor- 

 tant species; Exogone hebes and E. verugera were 

 also collected extensively. The March samples 

 contained a large number of individuals of 

 Euchone spp. and Chone spp. This represented the 

 first time in our offshore sampling that a suspen- 

 sion feeding polychaete group contributed more 

 than an occasional rare individual, although these 

 small sabellid species are probably not typical 

 suspension-feeding polychaetes (M.H. Pettibone 

 pers. commun.). Euchone spp. were present in 13 

 samples, and species of Chone spp. were dominant 

 in two of the five samples in which they were 

 collected. 



Goniadella gracilis was a dominant form in all 

 the offshore stations and in all sampling periods. It 

 was present in more than 65% of the samples in 

 May and November, with average occurrences of 

 297 individuals/m^ and 693 individuals/m^, re- 

 spectively. In the May samples, it was reduced to 

 32% of the samples with fewer numbers of indi- 

 viduals. However, it still remained the second- 

 most important polychaete species. 



Members of the family Sigalionidae occurred 

 more frequently and in higher densities in the 

 offshore samples than in the bay and nearshore 

 areas. Sthenelais boa and S. limicola occurred in 

 Delaware Bay in salinities >25%o, as well as in the 

 nearshore and offshore communities. Pholoe 

 minuta and Sigalion arenicola were present only 

 in the coastal and offshore stations. Sigalion 

 arenicola occurred in 12% of the November 

 offshore samples, with many individuals being 

 juveniles. None of these scale worms were ever 

 found in large numbers in any sample. The in- 

 crease in sigalionids offshore was not matched by 

 the other major scale worm family, the 

 Polynoidae. Polynoids were extremely numerous 

 in the bay, particularly in the epifaunal-infaunal 

 communities. In the offshore marine areas, only 

 Harmothoe extenuata was present. The absence of 

 collections from hard substrate offshore may affect 

 the average numbers of offshore polynoids. The 

 Sigalionidae typically are burrowing forms and 

 may find the fine sandy substrate more suitable 

 than do the polynoids. 



Maldanids were important in the three seasonal 

 offshore sampling periods. Most of the individuals 

 collected were juveniles, and thus difficult to iden- 

 tify. Most adult specimens were Clymenella 

 zonalis, C. torquata, and C. mucosa. 



219 



