Quantitative Composition and Distribution of the 

 Macrobenthic Invertebrate Fauna of the Continental Shelf Ecosystems 



of the Northeastern United States 



ROGER B. THEROUX* 

 ROLAND L. WIGLEY * 



Woods Hole Laboratory 



Northeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



Woods Hole, Massachusetts 02543 



ABSTRACT 



From the mid-1950s to the mid-1 960's a series of quantitative surveys of the macrobenthic 

 invertebrate fauna were conducted in the offshore New England region (Maine to Long 

 Island, NewYork). The surveys were designed to 1) obtain measures of macrobenthic 

 standing crop expressed in terms of density and biomass; 2) determine the taxonomic 

 composition of the fauna (ca. 567 species): 3) map the general features of macrobenthic 

 distribution; and 4) evaluate the fauna's relationships to water depth, bottom tvpe, tempera- 

 ture range, and sediment organic carbon content. A total of 1,076 samples, ranging from 3 

 to 3,974 m in depth, were obtained and analyzed. 



The aggregate macrobenthic fauna consists of 44 major taxonomic groups (phyla, 

 classes, orders). A striking fact is that only five of those groups (belonging to four phyla) 

 account for over 80% of both total biomass and number of individuals of the macrobenthos. 

 The five dominant groups are Bivalvia, Annelida, Amphipoda, Echninoidea, and 

 Holothuroidea. 



Other salient features pertaining to the macrobenthos of the region are the following: 

 substantial differences in quantity exist among different geographic subareas within the 

 region, but with a general trend that both densitv and biomass increase from northeast to 

 southwest; both densitv and biomass decrease with increasing depth; the composition of the 

 bottom sediments significantlv influences both the kind and quantity of macrobenthic 

 invertebrates, the largest quantities of both measures of abundance occurring in the coarser 

 grained sediments and diminishing with decreasing particle size; areas with marked sea- 

 sonal changes in water temperature support an abundant and diverse fauna, whereas a 

 uniform temperature regime is associated with a sparse, less diverse fauna; and no detect- 

 able trends are evident in the quantitative composition of the macrobenthos in relation to 

 sediment organic carbon content. 



Introduction 



The broad continental shelf off the northeastern coast 

 of the United States is a particularly significant topo- 

 graphic feature of the continental margin because of its 

 influence on the marine life of the region. Water masses 

 overlying this large shelf, and neritic waters generally, 

 are noted for their abundance of plankton, fishes, and 

 associated organisms, some endangered. Noteworthy 

 of the offshore New England waters, including Georges 

 Bank, are the rich harvests offish that have been taken 



each year since pre-Colonial days. The marine life in- 

 habiting New England offshore waters has been the 

 subject of studies conducted from time to time through- 

 out the past century. This has resulted in the acquisi- 

 tion of a considerable body of knowledge on the fishes 

 and plankton in this region, but information about the 

 benthic invertebrates has been rather limited, espe- 



* Present address: P.O. Box 306 East Flamouth , MA 02536. 

 **Present address: 35 Wilson Road, Woods Holt-, MA 02543. 



