Date of Award

Spring 2012

Project Type

Dissertation

Program or Major

Earth and Environmental Science

Degree Name

Doctor of Philosophy

First Advisor

David Burdick

Abstract

Anthropogenic activities in New England salt marshes have altered hydrologic flows in various ways, but unintended consequences from some of these habitat modifications have received little attention. Specifically, ditches have existed on salt marshes for decades, but the effects of these hydrologic alterations are only poorly understood. Ditch-plugging is a more recent methodology used for salt marsh habitat enhancement and mosquito control, but the long-term effects from this management practice are also unclear. I used natural tidal creeks and pools as controls to examine the effects resulting from ditching and plugging, respectively, on hydrology, soil characteristics, marsh surface elevation, plant characteristics, fish productivity, and trophic webs. Results indicated only slight differences in parameters sampled within habitat adjacent to ditches compared with creeks, and I infer minor ecological impact after 70+ years. Significant differences in hydrology, soil characteristics, marsh surface elevation, plant characteristics, fish productivity and trophic webs were observed in habitat adjacent to natural pools compared with ditch-plugs, and the many structural differences appear to result in ecological dissimilarities in function between the two habitats as well. The results of my study are important for natural resource managers to consider when planning salt marsh restoration and enhancement projects. The long-term legacy of ditch-plugs, especially as they pertain to changes in climate, may increase vulnerability of salt marshes to sea level rise and this conversion of ditches to ditch-plugs should not be undertaken without careful consideration.

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