agers because of its proximity to the coast and its potential as a 

 oppositional sink of contaminants. Although there are a 

 number of review documents dealing with benthos off south- 

 ern New England (Pratt 1973; TRIGOM-PARC; Wigley and 

 Theroux"- 9 ; Maurer 10 ), no study has featured the fauna of the 

 Mud Patch. 



MATERIALS AND METHODS 



Field and Laboratory 



Samples were collected 11-20 June 1962 by the National 

 Marine Fisheries Service vessel RV Delaware at 64 stations 

 south of Martha's Vineyard, Mass. (Fig. 1, Appendix Table 

 1). Stations were spaced at intervals of 16 km on a grid pattern 

 with eight north-south transects at right angles to the depth 

 contours. At each station (except station 7) two quantitative 

 bottom samples were collected with a Smith-Mclntyre grab. 

 This instrument effectively sampled a 0.1 m 2 area of bottom to 

 a depth of 10-17 cm. At sea, grab samples for macrobenthic 

 studies were washed through a 1.0 mm mesh screen. Macro- 

 benthos remaining on the screen after washing were removed 

 and preserved in a solution of neutral Formalin. 



In the laboratory macrobenthos were sorted, identified, 

 counted, and weighed. External moisture was removed from 

 specimens by blotting. Shells, internal skeletons, and exo- 

 skeletons were included in the values expressed as wet weight 

 biomass(g/m 2 ). 



Sediment samples were collected with a Dietz-LaFond grab 

 at each station and at two localities equally spaced between 

 stations along the cruise. The locations of sediment samples 

 used in conjunction with biological analyses are depicted in 

 Figure 1. Terminology follows the Wentworth Particle Size 

 Classification (Twenhofel and Tyler 1941), and nomenclature 

 follows the classification of Shepard (1954) and Emery (1960). 

 Determinations were made of median sediment size (§), percent 

 sand, percent silt, percent clay, percent Kjeldahl nitrogen, per- 

 cent organic carbon measured, and carbon/nitrogen ratio of 

 the sediments (Hathaway "). Standard sieving procedures were 

 used to measure sediment size. Based on sediment analyses, a 

 composite sediment-type map was made (Fig. 2). Appendix 

 Table 1 lists environmental data per station. 



'TRIGOM-PARC. 1974. A socio-economic and environmental inventory of the 

 North Atlantic Region, Vol. l,Book3, 198 p. Report to the Bureau of Land Man- 

 agement, South Portland, Me. 



"Wigley, R. L., and R. B. Theroux. 1976. Macrobenthic invertebrate fauna of 

 the Middle Atlantic Bight region. Part II: Faunal composition and quantitative 

 distribution. Northeast Fisheries Center, NMFS, Woods Hole, Mass., 395 p. 



'Wigley, R. L., and R. B. Theroux. Reconnaissance survey of the quantitative 

 distribution of macrobenthic invertebrates in the offshore New England region. 

 Manuscr. in prep. Northeast Fisheries Center, NMFS, Woods Hole, Mass. 



"Maurer, D. 1982. Review of benthic invertebrates of Georges Bank in relation 

 to gas and oil exploration with emphasis on management implications. Report to 

 Northeast Fisheries Center, Woods Hole, Mass., and Sandy Hook Laboratory, 

 Highlands, N. J., 329 p. 



' ' Hathaway, J. C. (editor). 1971 . Data file, continental margin program, Atlan- 

 tic Coast of the United States. Vol. 2. Sample collection and analytical data. Ref . 

 No. 71-15, 496 p. Woods Hole Oceanographic Institution, Woods Hole, Mass. 



Analysis 



Wet weight and number per t&xon by station and gear were 

 punched on cards and a computer listing was prepared. Based 

 on the listing, the average biomass and density per station of 

 major taxa (Amphipoda, Pelecypoda, Asteroidea, etc.) were 

 determined and distribution maps plotted by computer 

 (Maurer and Wigley footnote 6). In some cases, maps were 

 also made of particularly important genera and species. Corre- 

 lation coefficients (R) were computed for average weight and 

 number transformed (log e (A' + 1)) of major taxa in relation 

 to environmental variables. 



ENVIRONMENTAL SETTING 



Physiography 



The Georges Bank area off New England is a submerged 

 northeast extension of the Atlantic Coastal Plain (Aaron' 2 ). 

 The Bank, which encompasses about 42,000 km 2 , is covered by 

 up to 200 m of water. The study area for this account (Fig. 1) 

 lies immediately southwest of the Bank. 



The study area encompasses about 130 km 2 and extends 

 across the continental shelf to the upper portion of the con- 

 tinental slope. Bottom topography is moderately smooth. 

 Water depths increase gradually and rather uniformly from 

 shore outward to the shelf break, about 120 m. The average 

 gradient of the continental slope off the Middle Atlantic Bight 

 varies from 2° to 7°(Milliman 1973); beyond the shelf break in 

 the study area, the depth gradient is relatively steep, averaging 

 4° (Wigley and Stinton 1973). The most distinguishing feature 

 on the shelf break is the number of gullies and canyons that 

 transect the slope (Fig. 1). 



Sediment Composition 



Six major sediment types occurred in the study area (Fig. 2). 

 Sand, silty sand, and sandy silt occurred over a large area, 

 whereas gravel-sand, sand-silt-clay, and silt were much less 

 widespread. Sand with some gravel (stations 1, 45, 47) covered 

 more than half the area, mainly in shallow water (0 to 60-80 m) 

 except in the eastern sector and in a narrow (6 km) band paral- 

 lel to and just below the outer periphery of the continental 

 shelf. In shallow water the sands were silt free and occasionally 

 mixed with large quantities of shell (mollusks and echinoderm 

 plates). Admixtures of silt occurred with the sand over most of 

 the remaining area. 



A large area (80 x 100 km) of fine-grain sediment (Mud 

 Patch) occurred in the southwestern sector (Fig. 2). A relative- 

 ly circular area of sand-silt-clay near its center was surrounded 

 by an inner band of sandy silt which grades to an outer band of 

 silty sand. Illite is normally the most important clay mineral, 

 and organic carbon is higher here than in the surrounding sand 

 (Appendix Table 1). This is the largest known natural area of 

 fine-grain sediment on the Middle Atlantic Shelf. Sediments 

 on the continental slope were dominated by silt and clay. 



l2 Aaron, J. M. 1980. A summary of environmental geologic studies in the Geor- 

 ges Bank area, United States northeastern Atlantic outer continental shelf, 1975- 

 1977. Executive Summary of the Final Report submitted to the Bureau of Land 

 Management. U.S.G.S., Woods Hole, Mass., 22 p. 



