Echinoidea. — Mean biomass and density of echinoids ranged 

 from 0. 1 to > 100 g/m 2 and 0. 1 to 399/m 2 . The distribution of 

 echinoids was primarily influenced by the distribution of two 

 species (Echinarachnius parma and Schizaster fragilis) (Maurer 

 and Wigley footnote 6). Echinarachnius parma influenced 

 echinoid biomass and density in shallower water, sand, and 

 low percent silt-clay, and S. fragilis was influenced in deeper 

 water, sandy-silt, and high silt-clay. 



Asteroidea. — Mean biomass and density of asteroids ranged 

 from 0.1 to >50 g/rrr and from 1-49/m 2 . Their distribution 

 was sporadic (Maurer and Wigley footnote 6), but grab sam- 

 ples are not the most effective way to collect large asteroids. 

 Characteristic species were Asterias vulgaris, Leptasterias sp., 

 Porania sp., Henricia sp. , Astropecten americanus, and Astro- 

 pecten sp. Asterias vulgaris represented a shallow-water spe- 

 cies, and Astropecten americanus was a deeper water species. 

 Mean biomass and density were positively associated with sedi- 

 ment size (J? = 0.32, R = 0.26). 



Mud Patch Fauna 



Earlier in this report, the southwest quadrant of the 

 Martha's Vineyard-Nantucket Shoals area was referred to as 

 the Mud Patch (Fig. 2). The following stations generally com- 

 prised the Mud Patch: Stations 23-25, 33-36, 38-42, 49-53, and 

 57-59. Average biomass for these stations was 123.7 g/m 2 , and 

 density was 1,536.2/m 2 , which is markedly lower than respec- 

 tive values of 245.7 g/m 2 and 3,008/m 2 for the entire Martha's 

 Vineyard-Nantucket Shoals area. 



Based on two BLM stations (1 and 2) in the shallow water 

 and clean sand of Martha's Vineyard-Nantucket Shoals area 

 (Fig. 1), the dominant polychaete species (in abundance and 

 frequency of occurrence) were Exogone hebes, Spiophanes 

 bombyx, Parapionosyllis longicirrala, Sphaerosyllis erinaceus, 

 Owenia fusiformis, Scalibregma inflatum, Aricidea 

 catherinae, and Spio pettiboneae (Maurer and Leathern 14 ). 



The Mud Patch was characterized by anthozoans, small-to- 

 medium size bivalves (Bathyarca pectunculoides, Nuculana 

 acuta, Yolida sapotilla, Nucula spp.), small-to-medium size 

 decapods (Catapagurus sharreri, Hyas coarctatus, Euprognatha 

 rastellifera, Munida iris), and a variety of generally small echi- 

 noderms (Amphilimna olivacea, Amphioplus macilentus, 

 Amphiura otteri, Havelockia scabra, Schizaster fragilis). 

 Based on two BLM stations (6 and 7) in sediment containing 

 32-37% silt-clay near the Mud Patch (Maurer and Leathern 

 footnote 14), dominant species were Paraonis gracilis, Cossura 

 longocirrata, Ninoe nigripes, Aricidea suecica, Nephtys incisa, 

 Tharyx annulosus, Terebellides stroemii, Maldanidae, and 

 Cirratulidae in the deeper water and silty-sand and sandy-silt. 

 Robert Reid" reported high numbers of the amphipod Ampe- 

 lisca agassizi from the Mud Patch in some 1980 collections to- 

 gether with other species cited above. This fauna contains a 

 high proportion of selective and non-selective deposit feeders, 

 both surface and buried, representing a typical soft-bottom 

 community. Echinoderms were particularly important as con- 



tributors to biomass in the Mud Patch. Because of their gener- 

 al mode of feeding, the biota of the Mud Patch would have 

 considerable potential for ingesting pollutants associated with 

 deposition of fine-grain sediment. 



DISCUSSION 



Ecological Relationships 



A summary of mean biomass and number of individuals of 

 major taxa in relation to depth, temperature, median sediment 

 size, and silt-clay is presented in Figure 6. Also contained in 

 Figure 6 age the range (biomass and number of individuals) of 

 each taxon per environmental variable, together with values of 

 average biomass and density plotted for a specific mid-range. 



Depth. — Biomass and density of polychaetes off Martha's 

 Vineyard were not significantly associated with depth. 

 However, for the Georges Bank area, the density of polychaetes 

 increased significantly with depth down to ~80 m with some 

 indication of reduction in biomass with depth (Maurer and 

 Leathern footnote 14). Off Martha's Vineyard, biomass and 

 density of molluscs combined were not significantly associated 

 with depth. However, the density of scaphopods increased sig- 

 nificantly with increasing depth and the biomass of pelecypods 

 decreased with depth. Biomass pattern of pelecypods with 

 depth was dominated by the distribution of A. islandica rang- 

 ing between 40 and 60 m. For Georges Bank, density of com- 

 bined molluscs increased with water depth (Maurer' 6 ). 



For combined crustaceans off Martha's Vineyard, mean 

 biomass decreased with depth. Mean density of cumaceans 

 and isopods was negatively associated with depth. Mean bio- 

 mass of amphipods decreased with increasing depth. Density 

 pattern of combined crustaceans was dominated by the distri- 

 bution of amphipods, whereas biomass pattern of combined 

 crustaceans was dominated by decapods. For Georges Bank, 

 mean biomass of amphipods decreased in deeper water 

 (Maurer footnote 16). 



For combined echinoderms off Martha's Vineyard, mean 

 biomass and density increased with depth. In another study, 

 the bathymetric distribution of echinoderms off the northern 

 Oregon coast was not as uniform, as low wet weights were ob- 

 tained from depths of 86-139 m and 1,189-1,234 m (Alton 

 1972). Mean biomass and density of ophiuroids increased with 

 depth off Martha's Vineyard. For Georges Bank, mean densi- 

 ty of combined echinoderms showed no significant relation- 

 ship with depth, but biomass decreased significantly in deeper 

 water (Maurer footnote 16). These relationships reflected the 

 fact that although density was relatively regular throughout 

 the depth range, larger species (sea stars and echinoids) oc- 

 curred in relatively shallow water, with smaller species (brittle 

 stars) in deeper water. 



Mean biomass and number of individuals of combined taxa 

 were high between and 100 m depths. Biomass and density 

 decreased with increasing depth, although these relationships 

 were not statistically significant. Off southern New England, 

 there was a marked reduction in density and biomass with 



; "Maurer, D., and W. Leathern. 1980. Ecological distribution of polychaetous 

 annelids of Georges Bank. CMS-1-80. College of Marine Studies, Univ. of Dela- 

 ware, Lewes, Del., 181 p. 



'Robert Reid, Northeast Fisheries Center Sandy Hook Laboratory, National 

 Marine Fisheries Service, NOAA, Highlands, NJ 07732, pers. commun. 1981. 



"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, NMFS, Woods Hole, Mass., and Sandy Hook Lab- 

 oratory, Highlands, N.J., 329 p. 



