Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Department

Oceanography

First Advisor

Charles T. Roman

Abstract

The Boston Harbor Islands National Recreation Area (BOHA) has an extensive intertidal zone, with 47% of the area composed of mixed-coarse substrate. Given anticipated climate change impacts such as sea level rise and ocean warming, and other stressors associated with the urban environment, the critical ecosystem functions provided by the dominant yet largely understudied mixed-coarse habitat are likely to be altered. To evaluate the benthic invertebrate communities of BOHA and to determine what environmental factors of the mixed-coarse substrate affect community structure, 87 sampling sites were distributed between wave-exposed and wave-protected shorelines between mean higher high water and mean lower low water. A series of physical and environmental data was collected from each site to describe the intertidal habitat, and the epifaunal macroinvertebrate (>1 mm) communities were sampled. We found that benthic epifaunal community structure and diversity differed significantly between wave-exposed and wave-protected sites based on a wave energy model that reflects storm events in the harbor, where diversity was higher at protected sites. We also found that environmental variables collectively explained up to 67% of the variation in community characteristics, with elevation, organic content, water content, and soil skewness individually explaining up to 56%, 30%, 42%, and 33% of the variation, respectively. Other variables also made significant but smaller contributions. Infaunal data analysis was inconclusive, likely as a result of ineffective sampling methods. Differences in crab and periwinkle sizes between wave-exposed and wave-protected groups were also inconclusive with the exception of Hemigrapsus sanguineus which had a larger carapace width on wave-exposed shores based on a wave energy model that reflects storm events. Together, these results illustrate the importance of analyzing multiple measures of community characteristics since community structure, density, richness, diversity, and size may respond differently to wave energy and other environmental factors. This study in its entirety also serves as an inventory for the National Park Service and as a baseline for on-going monitoring efforts in response to climate change, invasive species, or other natural or anthropogenic disturbances.

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