Date of Award

8-2006

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Joseph Kelley

Second Committee Member

Robert Steneck

Third Committee Member

Michele Dionne

Abstract

Salt pools are shallow depressions in salt marshes that remain flooded throughout the entire tidal cycle. Though they are common landforms of this ecosystem, little is known about their characterization, formation, and development over time. Understanding the ontogeny of salt pools is critical, as it is suggested that they may serve as indicators of initial marsh break-up and ultimate wetland loss. Early hypotheses regarding pool initiation suggested that pools are primary features of marshes, while other hypotheses have suggested that pools form via secondary mechanisms such as isolated vegetative die-off, ice-plucking, or tidal creek abandonment. This study combines field observations, geologic coring, and spatio-temporal analyses of a time-series of aerial photographs through geographic information systems (GIs), to quantify the recent history of pools of the Webhannet Estuary, Wells, ME, USA. During the summers of 2004/2005 I sampled 119 pools along six transects. A Principle Components Analysis revealed three distinct pool types, though subsequent spatial analyses revealed no strongly associated trends in space or pool shape with pool type. Analyses of 50 pools from aerial photographs (1962, 1977, 1991,2003) show that most pools are highly dynamic in size and shape, that some pools exhibit progressive changes in shape, and that road construction greatly altered flooding and drainage patterns over the 41-year time period. Eight Dutch cores reveal a distinct pool signature in peat deposits, suggest that some pools are of a more ephemeral nature than previously described, and support the hypothesis that pools in the study area generally form via secondary mechanisms. These findings suggest that pools may contribute to marsh fragmentation, but it is unclear how they may contribute to overall wetland loss. An understanding of the role of pools in marsh loss/growth may have practical management implications and is worth exploring in greater depth.

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