Nineteen sediment cores were collected from five salt marshes on the northern shore of Cape Cod where previously restricted tidal exchange was restored to part of the marshes. Cores were collected in duplicate from two locations within each marsh complex: one upstream and one downstream from the former tidal restriction (typically caused by an undersized culvert or a berm). The unaltered, natural downstream sites provide a comparison against the historically restricted upstream sites. The sampled cores represent a chronosequence of restoration occurring between 2001–10. Collected cores were up to 168 cm in length with dry bulk density ranging from 0.04 to 2.62 grams per cubic centimeter and carbon content 0.12 % to 48.91 %. Land surface elevation was measured at each site (ranging from 0.484 meters to 1.51 meters relative to NAVD88) to determine the boundaries of each site within current tidal conditions. Gamma counting results for excess lead-210 were used to construct Constant Rate of Supply age models to date individual depth intervals in the core. Additionally, gamma counting results for other radionuclides, particularly cesium-137, gave further insight to evaluate how vertical accretion and carbon burial rates have changed during the past century. Carbon isotopes were measured to evaluate organic matter source.

Nineteen sediment cores were collected from five salt marshes on the northern shore of Cape Cod where previously restricted tidal exchange was restored to part of the marshes. Cores were collected in duplicate from two locations within each marsh complex: one upstream and one downstream from the former tidal restriction (typically caused by an undersized culvert or a berm). The unaltered, natural downstream sites provide a comparison against the historically restricted upstream sites. The sampled cores represent a chronosequence of restoration occurring between 2001–10. Collected cores were up to 168 cm in length with dry bulk density ranging from 0.04 to 2.62 grams per cubic centimeter and carbon content 0.12 % to 48.91 %. Land surface elevation was measured at each site (ranging from 0.484 meters to 1.51 meters relative to NAVD88) to determine the boundaries of each site within current tidal conditions. Gamma counting results for excess lead-210 were used to construct Constant Rate of Supply age models to date individual depth intervals in the core. Additionally, gamma counting results for other radionuclides, particularly cesium-137, gave further insight to evaluate how vertical accretion and carbon burial rates have changed during the past century. Carbon isotopes were measured to evaluate organic matter source.

The Herring River estuary in Wellfleet, Cape Cod, Massachusetts, has been tidally restricted for more than a century by a dike constructed near the mouth of the river. Upstream from the dike, the tidal restriction has caused the conversion of salt marsh wetlands to various other ecosystems including impounded freshwater marshes, flooded shrub land, drained forested upland, and brackish wetlands dominated by Phragmites australis. This estuary is now managed by the National Park Service, which plans to replace the aging dike and restore tidal flow to the estuary. To assist National Park Service land managers with restoration planning, the U.S. Geological Survey collected fourteen sediment cores from different ecosystems within the tidally restricted Herring River estuary (four sites) and an estuary in Wellfleet Harbor near the Herring River dike (three sites) between 2015 and 2017. Collected cores were up to 70 cm in length with dry bulk density ranges from 0.03 to 2.39 grams per cubic centimeter and carbon content 0.23% to 46.25%. Land surface elevation was measured at each site (ranging from -0.149 meters to 1.494 meters relative to NAVD88) to determine the boundaries for each site within current tidal conditions. Gamma counting results for excess lead-210 were used to construct Constant Rate of Supply (CRS) age models to age-date individual depth intervals in the cores. Additionally, gamma counting results for other radionuclides, particularly cesium-137 gave further insight to evaluate how vertical accretion and carbon burial rates have changed during the past century. This dataset can help evaluate differences among the varied ecosystems and vegetation types to make predictions about potential changes as tidal restoration commences in the Herring River estuary.

Accurate data and maps of sea floor geology are important first steps toward protecting fish habitat, delineating marine resources, and assessing environmental changes due to natural or human impacts. To address these concerns the U.S. Geological Survey, in cooperation with the Massachusetts Office of Coastal Zone Management (CZM), comprehensively mapped the Cape Cod Bay sea floor to characterize the surface and shallow subsurface geologic framework. Geophysical data collected include swath bathymetry, backscatter, and seismic reflection profile data. Ground-truth data, including sediment samples, underwater video, and bottom photographs were also collected. This effort is part of a long-term collaboration between the USGS and the Commonwealth of Massachusetts to map the State's waters, support research on the Quaternary evolution of coastal Massachusetts, the influence of sea-level change and sediment supply on coastal evolution, and efforts to understand the type, distribution, and quality of subtidal marine habitats. This collaboration produces high-resolution geologic maps and Geographic Information System (GIS) data that serve the needs of research, management and the public. Data collected as part of this mapping cooperative continue to be released in a series of USGS Open-File Reports and Data Releases (https://www.usgs.gov/centers/whcmsc/science/geologic-mapping-massachusetts-seafloor). This data release provides the geophysical and geologic sampling data collected in Cape Cod Bay during USGS Field Activities 2019-002-FA and 2019-034-FA in 2019.

Sediment cores were collected from three sites within the Plum Island Ecosystems Long-Term Ecological Research (PIE-LTER) domain in Massachusetts to obtain estimates of long-term marsh decomposition and evaluate shifts in the composition and reactivity of sediment organic carbon in disturbed marsh environments. Paired sediment cores were collected from three sites on the marsh platform and from three ponds; these cores were about 100 and 50 centimeters in length, respectively. The marsh sites had similar elevations, at about 1.41 to 1.51 meters relative to the North American Vertical Datum of 1988, and similar salt marsh grass communities, dominated by Spartina patens, S. alterniflora, and Distichlis spicata. Permanently inundated ponds within each site had comparable depths (0.24–0.30 meters) but varied in size (between 643 and 7,149 square meters; Spivak et al., 2017, 2018). The U.S. Geological Survey analyzed radioisotope concentrations for lead-210, radium-226, cesium-127, and beryllium-7 from six marsh cores and three pond cores to develop an age model for each core. This data release includes calculated percent dry bulk density and raw radioisotope data for these cores. Spivak, A.C., Gosselin, K., Howard, E., Mariotti, G., Forbrich, I., Stanley, R., and Sylva, S.P., 2017, Shallow ponds are heterogeneous habitats within a temperate salt marsh ecosystem: Journal of Geophysical Research-Biogeosciences, 122(6), 1371-1384. Spivak, A. C., Gosselin, K. M., and Sylva, S.P., 2018, Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems: Limnology and Oceanography, 63(4), 1622-1642.

Sediment cores were collected from three sites within the Plum Island Ecosystems Long-Term Ecological Research (PIE-LTER) domain in Massachusetts to obtain estimates of long-term marsh decomposition and evaluate shifts in the composition and reactivity of sediment organic carbon in disturbed marsh environments. Paired sediment cores were collected from three sites on the marsh platform and from three ponds; these cores were about 100 and 50 centimeters in length, respectively. The marsh sites had similar elevations, at about 1.41 to 1.51 meters relative to the North American Vertical Datum of 1988, and similar salt marsh grass communities, dominated by Spartina patens, S. alterniflora, and Distichlis spicata. Permanently inundated ponds within each site had comparable depths (0.24–0.30 meters) but varied in size (between 643 and 7,149 square meters; Spivak et al., 2017, 2018). The U.S. Geological Survey analyzed radioisotope concentrations for lead-210, radium-226, cesium-127, and beryllium-7 from six marsh cores and three pond cores to develop an age model for each core. This data release includes calculated percent dry bulk density and raw radioisotope data for these cores. Spivak, A.C., Gosselin, K., Howard, E., Mariotti, G., Forbrich, I., Stanley, R., and Sylva, S.P., 2017, Shallow ponds are heterogeneous habitats within a temperate salt marsh ecosystem: Journal of Geophysical Research-Biogeosciences, 122(6), 1371-1384. Spivak, A. C., Gosselin, K. M., and Sylva, S.P., 2018, Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems: Limnology and Oceanography, 63(4), 1622-1642.

Continuous monitoring data reported are a portion of data from a larger study investigating changes in soil properties, carbon accumulation, and greenhouse gas fluxes in four recently restored salt marsh sites and nearby natural salt marshes. For several decades, local towns, conservation groups, and government organizations have worked to identify, replace, repair, and enlarge culverts to restore tidal flow upstream from historical tidal restrictions in an effort to restore salt marsh ecosystems on Cape Cod, Massachusetts. Undersized or failed culverts restrict tidal exchange between the marsh and the bays and estuaries, which leads to alterations in plant community composition and in fundamental processes controlling soil carbon accumulation, soil carbon transformations, and greenhouse gas emissions. In this study, sites were selected to compare salt marshes restored over a range of years and to compare marshes upstream and downstream from a restored tidal restriction. Salt marshes downstream from tidal restrictions represent "natural" conditions because hydrology was not substantially altered, whereas marshes upstream from repaired culverts represent "restored" conditions. At each of the four salt marsh sites, study plots were established on the natural and restored sides of the former tidal restriction. Well water-level loggers, soil and air temperature loggers, and photosynthetically active radiation (PAR) sensors were deployed over the growing season to coincide with discrete measurements of greenhouse gas fluxes made by study collaborators. Water-level loggers were also deployed in creeks near the restored tidal restriction.

Continuous monitoring data reported are a portion of data from a larger study investigating changes in soil properties, carbon accumulation, and greenhouse gas fluxes in four recently restored salt marsh sites and nearby natural salt marshes. For several decades, local towns, conservation groups, and government organizations have worked to identify, replace, repair, and enlarge culverts to restore tidal flow upstream from historical tidal restrictions in an effort to restore salt marsh ecosystems on Cape Cod, Massachusetts. Undersized or failed culverts restrict tidal exchange between the marsh and the bays and estuaries, which leads to alterations in plant community composition and in fundamental processes controlling soil carbon accumulation, soil carbon transformations, and greenhouse gas emissions. In this study, sites were selected to compare salt marshes restored over a range of years and to compare marshes upstream and downstream from a restored tidal restriction. Salt marshes downstream from tidal restrictions represent "natural" conditions because hydrology was not substantially altered, whereas marshes upstream from repaired culverts represent "restored" conditions. At each of the four salt marsh sites, study plots were established on the natural and restored sides of the former tidal restriction. Well water-level loggers, soil and air temperature loggers, and photosynthetically active radiation (PAR) sensors were deployed over the growing season to coincide with discrete measurements of greenhouse gas fluxes made by study collaborators. Water-level loggers were also deployed in creeks near the restored tidal restriction.

The accretion history of fringing salt marshes in Narragansett Bay, Rhode Island, was reconstructed from sediment cores. Age models, based on excess lead-210 and cesium-137 radionuclide analysis, were constructed to evaluate how vertical accretion and carbon burial rates have changed during the past century. The Constant Rate of Supply (CRS) age model was used to date six cores collected from three salt marshes. Both vertical accretion rates and carbon burial increased from 1900 to 2016, the year the data were collected. Cores were up to 90 cm in length with dry bulk density ranging from 0.07 to 3.08 grams per cubic centimeter and carbon content 0.71 % to 33.58 %.

The accretion history of fringing salt marshes in Narragansett Bay, Rhode Island, was reconstructed from sediment cores. Age models, based on excess lead-210 and cesium-137 radionuclide analysis, were constructed to evaluate how vertical accretion and carbon burial rates have changed during the past century. The Constant Rate of Supply (CRS) age model was used to date six cores collected from three salt marshes. Both vertical accretion rates and carbon burial increased from 1900 to 2016, the year the data were collected. Cores were up to 90 cm in length with dry bulk density ranging from 0.07 to 3.08 grams per cubic centimeter and carbon content 0.71 % to 33.58 %.