Recycled glass cullet is a potential alternative to fill substrate in salt marsh restoration projects, given its similarity to natural silica sands. However, the ability for common salt marsh plants to grow in glass cullet has not yet been tested. An outdoor mesocosm experiment assessed the ability of the dominant mid-marsh plant Juncus roemerianus and the upland marsh plant Spartina patens to grow in various mixtures of glass cullet versus fill soil. Results showed that J. roemerianus can survive in glass cullet, but growth declined as the proportion of cullet increased. However, S. patens grew comparably, if not better, in treatments up to 75% glass cullet. In the face of increased coastal land loss and a global sediment deficit, the use of glass cullet in upland salt marsh restoration projects can simultaneously divert glass from landfills and promote more sustainable coastal restoration strategies along the northern Gulf of Mexico.

Thesis advisor: Noah P. Snyder / Though previous studies have shown saltmarsh adaptability to some degree of sea-level rise (SLR), sediment supply is critical to sustaining saltmarshes as SLR accelerates. Land-use activities, such as dams, often influence watershed sediment transport and delivery to the coast. Previous studies have suggested that, even in small watersheds, dams can significantly impact coastal sediment budgets. The Parker River watershed (PRW) in northeastern Massachusetts hosts 20 dams and several natural lakes, and drains into the Plum Island Sound Estuary (PIE). This research aims to evaluate the impact of dams and sediment transport in the PRW. Three approaches were used: theoretical modeling of sediment transport patterns using digital elevation models; spatial analysis of suspended sediment concentration (SSC) and remote sensing data; and empirical calculations of reservoir trap efficiency. Geomorphic modeling indicates that bankfull discharge can transport 20 μm grains (silt) as wash load throughout the PRW. Sediment deposition might happen at Crane Pond and in reservoirs, but removing dams would not change this pattern. Both SSC data and observations of satellite images during high-flow events indicate low supply and transport of sediment throughout the PRW. The estimates of sediment yield (Y) are low for the PRW. An empirical calculation indicates little-to-no trap efficiencies for all dams. Therefore, fluvial contribution to the sediment budget of the PIS estuary is limited and dam removals in the PRW are unlikely to change the rate of sediment delivery to the PIE. The proposed method of this study provides an additional scope to assess the ecological benefits of removing a dam and could be easily replicated for other locations for similar assessment. Future studies should assess sediment dynamics and management practices from a more thorough perspective incorporating the riverine, estuarine and shelf system. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.