Date of Award

5-2005

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Leslie Watling

Second Committee Member

Peter Jumars

Third Committee Member

Joseph Kelley

Abstract

Physical disturbance plays a large role in maintaining diversity within softsediment marine benthic communities. Benthic community structure at Stellwagen Bank National Marine Sanctuary was examined following two sources of anthropogenic physical disturbance. Reference sites were designated based on the presence or absence of commercial fishing activity (primarily bottom trawls and dredges), as well as the burial of a fiber-optic telecommunications cable. The objectives of this study were to: (1) evaluate the impact of mobile bottom-contact fishing gear on soft-sediment community structure and sediment composition, and (2) evaluate the impact of the Hibernia fiberoptic cable, buried in September 2000, on soft-sediment community structure. Sediment samples were collected in both mud (∼140 m) and sand (∼30 to 40 m) commercial fishing reference sites using a Smith-Mchtire grab during the summers of 2001 and 2002, following the closure of the Western Gulf of Maine Closure Area (WGoMCA), which was closed in May 1998. Photographic and video transects were conducted at all reference sites using remotely operated vehicles (ROVs) and the Sanctuary's Integrated Seafloor Imaging System (ISIS). Results indicate that both infaunal and epifaunal communities differed between fished and unfished sites in both mud and sand habitats. Significant decreases in the abundance of sea stars and tube-building taxa in the disturbed mud site resulted in an overall higher abundance of organisms in the undisturbed site. An additive response of all taxa was responsible for the difference between infaunal communities in the sand habitat, whereas significant differences in sponge and scallop abundances were primarily responsible for dissimilarity in epifaunal communities. Both habitats also had several taxa differing in abundance between sampling years. Epifaunal communities had a different response to cable burial depending on the presence of fishing activity. Communities on and off the cable route were similar to one another within the WGoMCA. Outside the closure, the exposure of hard substrate during cable burial, along with continued resuspension from fishing activity, appeared to benefit sessile organisms that utilize hard substrate for attachment.

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