Dataset: Continuously monitored water quality parameters from three open-water sites in a tidal salt marsh channel in New Jersey, USA from June 2021 to June 2024

This dataset follows the methodology described in Chua et al. (2025). Continuous water quality monitoring was conducted at three observational open-water platforms located within the main marsh channel of SMIIL. Each platform was outfitted with Aqua TROLL 600 multiparameter sondes (In-Situ Inc.), configured to measure a suite of environmental variables including water depth, temperature, salinity, dissolved oxygen (DO), pH, chlorophyll a fluorescence, turbidity. Two sondes were mounted on a fixed pole at each platform and deployed near the bottom of the water column (in water depths <2 m). Salinity, temperature, DO, and pH were measured in duplicate to ensure data quality and redundancy. Each sonde was also configured with either a chlorophyll a or turbidity sensor, allowing coverage of all target variables across platforms. Sondes were retrieved and replaced with pre-cleaned, newly calibrated sondes every 4–12 weeks. Data were downloaded during each maintenance visit using the VuSitu Mobile App (In-Situ Inc.). Although sondes were initially configured for remote telemetry, persistent data dropout issues led to a switch to internal data logging by June 2022. Discrete surface water samples for DO, dissolved inorganic carbon (DIC), and total alkalinity (TA) were also collected during maintenance visits, starting in September 2022 (Supino et al., 2025). These samples were used to validate the Aqua TROLL DO and pH data (see Data Procession section).

Meteorological data were also collected at SMIIL to complement the water quality dataset. A ResponseONE™ Weather Transmitter (R.M. Young Company) measured wind speed and direction, air temperature, relative humidity, and atmospheric pressure. Due to data transmission issues, this record only spans September 2021–May 2023. Additionally, a nearby HOBO water level logger (Onset Computer Corp.) recorded air temperature and atmospheric pressure from August 2022–June 2024. Data from both sensors were combined to produce a continuous record of air temperature and atmospheric pressure spanning the full duration of water quality measurements. To estimate surface wind speed over the study period, hourly 10-m u- and v-component wind data were obtained from the fifth generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5; Hersbach et al., 2023) for the grid cell closest to 39.04^oN, 74.79^oW. The ERA5-derived wind speeds were used in subsequent analyses due to their close agreement with field measurements from the ResponseONE™ station.