KINNER and MAURER: POLYCHAETOUS ANNELIDS OF DELAWARE BAY 



pies produced 13 specimens of Nephtys picta. No 

 other species was represented by more than one or 

 two individuals. In the 20 dredge hauls taken at 

 the same location, N. incisa was present in almost 

 all samples in densities great enough to be consid- 

 ered a dominant organism in the community. 

 Sanders (1958) described a muddy sand commun- 

 ity from Buzzards Bay as a Nucula proxima- 

 Nephtys incisa group. The sampling in Delaware 

 Bay indicated that A^. incisa was not sufficiently 

 dominant to be a characteristic species for this 

 community. The other two muddy sand stations 

 contained A^. incisa, A. oculata, Scoloplos robus- 

 tus, S. fragilis, Spio setosa, and Glycinde solitaria 

 as important polychaete species throughout the 

 year. 



EPIFAUNAL-INFAUNAL ASSEMBLAGES.— 

 The epifaunal-infaunal assemblages include a 

 calcareous serpulid assemblage; a polymodal sed- 

 iment, which contained a mussel community; and 

 the oyster community. These epifaunal-infaunal 

 assemblages are pooled here because certain in- 

 faunal species occurred only in samples contain- 

 ing the epifaunal assemblages. The latter also 

 contributed to the formation of the sediment con- 

 taining particular species of infauna. 



Blue Mussel Assernblage. — The blue mussel, 

 Mytilus edulis, was the primary species in an 

 epifaunal-infaunal assemblage in lower Delaware 

 Bay (C). The assemblage was transitory and de- 

 pended on the life cycle of the mussels and physical 

 disturbances such as storms. The substratum be- 

 neath the Mytilus beds consisted of a poorly sorted 

 polymodal sediment. The mussels were first col- 

 lected as juveniles in May. Their growth over the 

 summer was accompanied by an increase in the 

 number of species of polychaetes as well as the 

 number of specimens. Mussels were almost absent 

 in November samples, with a corresponding de- 

 crease in numbers of species and individuals of 

 polychaetes. There was a reappearance of the 

 mussel beds the following May. A total of 49 

 species of polychaetes were collected in the 

 Mytilus beds, ranging from 5 to 22 species/sample. 

 The most common species living on the mussels 

 and among the byssal threads included Har- 

 mothoe extenuata and Nereis succinea. Other im- 

 portant members of the epifauna were 

 Lepidonotus squamatus, L. sublevis, Eumida san- 

 guinea, Polydora ligni, Polycirrus eximius, and 

 Eteone heteropoda. The infaunal species were 



dominated by Mediomastus ambiseta, Spio setosa 

 (which occurred in 609c of the samples), and 

 Asabellides oculata. Aricidea catherinae, Streb- 

 lospio benedicti, Tharyx spp., and Chaetozone spp. 

 also contributed significantly to the infaunal 

 community. During the winter there was a reduc- 

 tion in the density and number of epifaunal 

 species. In the spring, when the young mussels 

 were still small, Spio setosa composed as much as 

 109c of the individuals of the samples, with over 

 5,000 individuals/m^. This type of opportunism by 

 the infaunal species was observed the preceding 

 spring to a lesser degree, when S. setosa made up 

 as much as 40^??^ of the specimens collected. 

 Steimle and Stone (1973) described a similar 

 Mytilus aggregation from off Long Island, N.Y. 

 where H. imbricata, H. extenuata, L. squamatus, 

 and N. succinea were the dominant polychaetes. 



Serpulid Assemblage. — A second major 

 epifaunal-infaunal assemblage in Delaware Bay 

 was a serpulid assemblage. Geological descrip- 

 tions of serpulid reefs have been reported from 

 England (Garwood 1931; Bosence 1973). Descrip- 

 tions of the biology of such assemblages formed by 

 Hydroides dianthus from the east coast of the 

 United States are unknown to us. Hydroides dian- 

 thus forms calcareous tubes encrusting shells and 

 rocks, with the distal part of the tube erect, away 

 from the substrate. Hydroides larvae then settle 

 on the adult tubes forming heads of tubes. This 

 assemblage does not form a continuous structure, 

 but a series of heads occurring over an area of 1 

 km^. Similar assemblages have also been observed 

 in Indian River Bay and Little Assawoman Bay, 

 but have not been studied to date. 



In addition to H. dianthus, the dominant 

 polychaetes of this assemblage were Sabellaria 

 vulgaris, Eumida sanguinea, Mediomastus am- 

 biseta, Asabellides oculata, and Polydora ligni. 

 Sabellaria vulgaris, which forms reefs of its own in 

 other areas of the bay (Curtis 1975), attached its 

 sandy tubes on the H. dianthus tubes. Polydora 

 ligni builds its muddy tubes in the crevices be- 

 tween the calcareous structures and in empty H. 

 dianthus tubes. Polycirrus eximius also exploited 

 the vacant tubes, while Harmothoe extenuata, L. 

 squamata, and L. sublevis primarily were found 

 wedged between the tubes. Marphysa sanguinea, 

 which was collected only rarely on the Mytilus 

 beds and nowhere else in the bay, was an impor- 

 tant member of the serpulid community. Asabel- 

 lides oculata, Glycinde solitaria, Mediomastus 



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