Tidal restriction and salt marsh drainage in the Herring River estuary : chemical and biological consequences
Evan Samuel Trebesch Heberlein
May 11, 2016
Department or Program
Biology - Environmental Studies
Freshwater flows out of the Herring River estuary at Cape Cod National Seashore have been restricted through a dike for nearly a century. Along with extensive salt marsh drainage efforts throughout the river’s small watershed, the dike’s tidal restriction has drastically altered geochemical transformations and the trophic structure of estuarine biota. Stagnant water conditions are prevalent throughout the upper estuary, leading to seasonal eutrophication. This thesis investigates the chemical and biological consequences of these ecosystem manipulations within a holistic examination of estuarine ecology and geochemical processes. Through the examination of water quality data collected during 2013-2015, this study corroborates past NPS findings on seasonal eutrophication, and presents strong evidence for the mobilization of metals from drained salt marsh sediments. Additional inquiries are made into potential mechanisms for autumnal acidification, the chemical implications of reduced salinity and oxygen levels, and the effects of stagnant, acidic, and reducing water conditions in the upper estuary.