Water level and salinity data for four sites in the coastal marsh at Grand Bay National Estuarine Research Reserve, Mississippi, from October 2016 through October 2017

Solinst LTC Levelogger Edge (Model 3001) M10 or M20 sensors were used to record water levels, conductivity and temperature. Before deployment, each sensor was programmed to record at a continuous 30- or 40-minute interval over the course of the 3-month deployment. In October 2016, 1.5-meter (m) long wells were installed at each of the four study sites so approximately 0.5 m of the wells were sticking out of the marsh or estuary surface. At the start of each trip the loggers were wrapped in a protective coating (plastic wrap, nylon stockings, and tape) and tied onto the well cap. Measurements of the string and logger length were collected for post-processing of the data. The logger was slowly lowered into the well and the well cap was secured. GPS position and elevation data were collected (using a differential GPS) on the top of the well cap and at the marsh surface next to the well.

After the initial deployment in October 2016, the water level loggers were collected and redeployed quarterly along with sediment plate deployments (January 2017, April 2017, July 2017, and October 2017). Each collection consisted of gently removing the logger from the well and noting if there was sediment in the well. If there was sediment in the well, it was cleaned and moved to a new location, a new water level logger was then placed inside the well. Measurements at the new location were collected for the string and logger as well as GPS coordinates and elevation.

Water level, temperature, and conductivity data were downloaded from the logger as raw uncorrected data. Data from local meteorological stations were obtained from the National Estuarine Research Reserve System Centralized Data Management Office. The raw data were run through an R Studio code. The code converted the date into Coordinated Universal Time (UTC), corrected the water level based on the sensor depth, converted the elevation data into the North American Vertical Datum of 1988 (NAVD88), derived salinity from temperature and conductivity, and clipped the data to a specified date range. Barometric pressure was used to correct level logger pressure data. Salinity was calculated using standard algorithms for computation of fundamental properties of seawater (Fofonoff and Millard Jr., 1983). Data were then adjusted using elevation information and compared to NOAA tide and currents station 8740166 and/or 8739803. Elevations include: 17CCT01 (Site 2 (-0.0934 m) and 3 (-0.881 m)), 17CCT02 (Site 1 (-1.0700 m), Site 2 (-0.0284 m) and 4 (-0.-0.8169 m)), 17CCT03 (Site 1 (-0.8396 m), 2 (-0.1284 m), 3 (-0.768 m), and Site 4 (-0.7306)), 17CCT04 (Site 1 (-0.8207 m), Site 2 (-0.0312 m), 3 (-0.744 m), and Site 4 (-0.5436)), and 17CCT05 (Site 3 (-0.7457 m)). The final data output format was a comma-separated (.csv) values file. The final water level data published in this data release are 17CCT01 (Site 2 and 3), 17CCT02 (Sites 1, 2, and 4), 17CCT03 (Site 1, 2, 3, and 4), 17CCT04 (Site 1, 2, 3 and 4), and 17CCT05 (Site 3). The sites not included in this data release were omitted due to sensor failure or excessive erroneous data. Some leveloggers showed evidence of severe data drift, which could not be substantiated, possibly due to sediment build-up within the well. Sites with sensor drift were corrected, if possible, and published as both corrected and uncorrected data. Sites with erroneous data that were not able to be corrected were also published for consistency with publishing standards. For information about data corrections and detrending contact the authors.

Added keywords section with USGS persistent identifier as theme keyword.