Sedimentation Rates in Flow-Restricted and Restored Salt Marshes in Long Island Sound

• Published in: Estuaries Vol. 22; no. 2; pp. 231 - 244
• Main Authors: Anisfeld, Shimon C., Tobin, Marcia J., Benoit, Gaboury
• Format: Journal Article
• Language: English
• Published: Lawrence, KS Estuarine Research Federation 01.06.1999; Springer Nature B.V
• Subjects: Accretion; Cores; Earth sciences; Earth, ocean, space; Environmental restoration; Estuaries; Exact sciences and technology; Geochronology; Isotope geochemistry. Geochronology; Marine; Marine and continental quaternary; Marine ecology; Marshes; Organic matter; Organic sediments; Population density; Porosity; Salt marshes; Sea level rise; Sedimentation & deposition; Sedimentation rates; Sediments; Sluices; Soil erosion; Subsidence; Surficial geology; Water levels; Wetland ecology; Long Island Sound; North Atlantic; United States; Northwest Atlantic; Connecticut; ANW, USA, Long Island Sound; ANW, USA, Connecticut; drill cores; modern; bulk density; salt marshes; Atlantic Ocean; carbon; Cs-137; marshes; dating; Pb-210; sedimentation rates; North America
• ISSN: 0160-8347; 1559-2723; 1559-2758; 1559-2731
• DOI: 10.2307/1352980

Many salt marshes in densely populated areas have been subjected to a reduction in tidal flow. In order to assess the impact of tidal flow restriction on marsh sedimentation processes, sediment cores were collected from flow-restricted salt marshes along the Connecticut coast of Long Island Sound. Cores were also collected from unrestricted reference marshes and from a marsh that had been previously restricted but was restored to fuller tidal flushing in the 1970's. High bulk densities and low C and N concentrations were found at depth in the restricted marsh cores, which we attribute to a period of organic matter oxidation, sediment compaction, and marsh surface subsidence upon installation of flow restrictions (between 100 and 200 years before the present, depending on the marsh). Recent sedimentation rates at the restricted marshes (as determined by 137 Cs and 210 Pb dating) were positive and averaged 78% (137 Cs) and 50% (210 Pb) of reference marsh sedimentation rates. The accumulation of inorganic sediment was similar at the restricted and reference marshes, perhaps because of the seasonal operation of the tide gates, while organic sediment accretion (and pore space) was significantly lower in the restricted marshes, perhaps because of higher decomposition rates. Sedimentation rates at the restored marsh were significantly higher than at the reference marshes. This marsh has responded to the higher water levels resulting from restoration by a rapid increase in marsh surface elevation.