Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted vast areas of coastal wetlands to tidal exchange. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here we present measurements of net ecosystem exchange of carbon dioxide (CO2) and methane, along with ancillary meteorological data, collected from coastal wetlands across Cape Cod to evaluate the effect of hydrological management and salinity on carbon exchange in coastal wetlands.

Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted vast areas of coastal wetlands to tidal exchange. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here we present measurements of net ecosystem exchange of carbon dioxide (CO2) and methane, along with ancillary meteorological data, collected from coastal wetlands across Cape Cod to evaluate the effect of hydrological management and salinity on carbon exchange in coastal wetlands.

This data release provides analytical and other data in support of an analysis of nitrogen transport and transformation in groundwater and in a subterranean estuary in the Eel River and onshore locations on the Seacoast Shores peninsula, Falmouth, Massachusetts. The analysis is described in U.S. Geological Survey Scientific Investigations Report 2018-5095 by Colman and others (2018). This data release is structured as a set of comma-separated values (CSV) files, each of which contains data columns for laboratory (if applicable), USGS Site Name, date sampled, time sampled, and columns of specific analytical and(or) other data. The .csv data files have the same number of rows and each row in each .csv file corresponds to the same sample. Blank cells in a .csv file indicate that the sample was not analyzed for that constituent. The data release also provides a Data Dictionary (Data_Dictionary.csv) that provides the following information for each constituent (analyte): laboratory or data source, data type, description of units, method, minimum reporting limit, limit of quantitation if appropriate, method reference citations, minimum, maximum, median, and average values for each analyte. The data release also contains a file called Abbreviations in Data_Dictionary.pdf that contains all of the abbreviations in the Data Dictionary and in the well characteristics file in the companion report, Colman and others (2018).

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.

This dataset provides the water content, bulk density, carbon concentrations, nitrogen concentrations, and carbon content of all fourteen cores sampled in coastal Louisiana (CRMS 0224) in October of 2019. Each sample is identified by a unique identifier that corresponds to each site by depth increment combination. The pond age range associated with each site is provided. The depth increment associated with each sample is provided.

The Massachusetts Office of Coastal Zone Management launched the Shoreline Change Project in 1989 to identify erosion-prone areas of the coast. The shoreline position and change rate are used to inform management decisions regarding the erosion of coastal resources. In 2001, a shoreline from 1994 was added to calculate both long- and short-term shoreline change rates along ocean-facing sections of the Massachusetts coast. In 2013, two oceanfront shorelines for Massachusetts were added using 2008-9 color aerial orthoimagery and 2007 topographic lidar datasets obtained from the National Oceanic and Atmospheric Administration's Ocean Service, Coastal Services Center. This 2018 data release includes rates that incorporate two new mean high water (MHW) shorelines for the Massachusetts coast extracted from lidar data collected between 2010 and 2014. The first new shoreline for the State includes data from 2010 along the North Shore and South Coast from lidar data collected by the U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise. Shorelines along the South Shore and Outer Cape are from 2011 lidar data collected by the U.S. Geological Survey's (USGS) National Geospatial Program Office. Shorelines along Nantucket and Martha’s Vineyard are from a 2012 USACE Post Sandy Topographic lidar survey. The second new shoreline for the North Shore, Boston, South Shore, Cape Cod Bay, Outer Cape, South Cape, Nantucket, Martha’s Vineyard, and the South Coast (around Buzzards Bay to the Rhode Island Border) is from 2013-14 lidar data collected by the (USGS) Coastal and Marine Geology Program. This 2018 update of the rate of shoreline change in Massachusetts includes two types of rates. Some of rates include a proxy-datum bias correction, this is indicated in the filename with “PDB”. The rates that do not account for this correction have “NB” in their file names. The proxy-datum bias is applied because in some areas a proxy shoreline (like a High Water Line shoreline) has a bias when compared to a datum shoreline (like a Mean High Water shoreline). In areas where it exists, this bias should be accounted for when calculating rates using a mix of proxy and datum shorelines. This issue is explained further in Ruggiero and List (2009) and in the process steps of the metadata associated with the rates.

These data include vertical profiles of concentrations and stable carbon isotope values of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total organic carbon (TOC) from sediment cores collected at methane seeps and reference sites. Sediment porosity and dissolved sulfate and methane concentrations are also presented. Methane seeps in Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent, along the Cascadia Margin, were sampled. These data were collected over two decades and across four cruises: PGC02-08 (CCGS John P. Tully, 2002), Hydrates 2004 Sea Trial (CCGS John P. Tully, 2004), AT50-14 (R/V Atlantis, 2023), and AT50-29B (R/V Atlantis, 2024).

The reconnaissance maps upon which this data set is based show the areal distribution of the major bottom sediment types covering the sea floor off Massachusetts between Cape Ann and Cape Cod. The maps were intended as a guide to the future mapping of gravel, sand, silt, and clay, and, because these sediments reflect the hydraulic conditions, they are also helpful for deducing the important sediment transport mechanisms.

In order to test hypotheses about groundwater flow under and into estuaries and the Atlantic Ocean, geophysical surveys, geophysical probing, submarine groundwater sampling, and sediment coring were conducted by U.S. Geological Survey (USGS) scientists at Cape Cod National Seashore (CCNS) from 2004 through 2006. Coastal resource managers at CCNS and elsewhere are concerned about nutrients that are entering coastal waters via submarine groundwater discharge, which are contributing to eutrophication and harmful algal blooms. The research carried out as part of the study described here was designed, in part, to help refine assumptions required by earlier versions of models about the nature of submarine groundwater flow and discharge at CCNS. This study was conducted in four phases, with a variety of field techniques and equipment employed in each phase. Phase 1 consisted of continuous resistivity profiling (CRP) surveys of the entire study area conducted in 2004. Phase 2 consisted of CRP ground-truthing via resistivity probe measurements and submarine groundwater sampling from hydraulically-drive piezometers using a barge in the Salt Pond/Nauset Marsh area in 2005. Phase 3 consisted of supplemental detailed CRP surveys in the Salt Pond/Nauset Marsh area in 2006. Finally, Phase 4 consisted of sediment coring and porewater extraction in the Salt Pond/Nauset Marsh area later in 2006 to supplement the 2005 sampling.

Gas fluxes (carbon dioxide, methane, nitrous oxide), sediment, environmental variables, nutrients, eelgrass and macroalgae data collected from coastal lagoons in southern Rhode Island in 2022 and 2023.