High-Resolution Seawater Greenhouse Gas Observations in Mangrove creeks and Seagrass meadows in Zanzibar (Tanzania)

This dataset presents field observations of seawater from a tidal seagrass meadow (Enhalus acoroides Linnaeus f.) and a tidal mangrove (dominated by Avicennia marina, (Shunula, 1996)) creek in Chwaka Bay, Tanzania. Measurements were collected during the wet season (November–December 2022) in a high temporal resolution. The dataset includes time series measurements of dissolved carbon dioxide (CO2) and methane (CH4), along with water depth, temperature, salinity, dissolved oxygen, pH, and radon concentration. All timestamps are reported in East Africa Time (EAT; UTC+03:00). Time series observations of CO2 and CH4 were measured using automated greenhouse gas analyzers (LI-COR LI-7810; 1 second intervals). The groundwater tracer radon measurements were performed with a radon-in-air analyzer (RAD7 Durridge Company; 30 minutes interval). Both instruments operated in a closed air loop equilibrated with a continuous stream of seawater (~3 L per minute) pumped through a showerhead gas exchanger (Santos et al., 2012). Water depth, water temperature and salinity (Solinst 3001 Levelogger 5), dissolved oxygen (MiniDOT oxygen logger, PME), and pH (HOBO MX2501 pH and Temperature Data Logger, ONSET) loggers were all calibrated before use. For consistency, all measurements were subsequently averaged to 15-minute intervals. The reported data were corrected for analytical time lags of 10 min for CO2, 30 min for CH4 and 30 min for radon concentrations. References Santos, I. R., Maher, D. T., & Eyre, B. D. (2012). Coupling Automated Radon and Carbon Dioxide Measurements in Coastal Waters. Environmental Science & Technology, 46(14), 7685-7691. https://doi.org/10.1021/es301961b Shunula, J. P. T. (1996). Ecological studies on selected mangrove swamps in Zanzibar. Master dissertation, University of Dar es Salaam. Available at (http://41.86.178.3/internetserver3.1.2/search.aspx?formtype=advanced) Funding The production of this data-set was funded by a grant from VR-Sida 2019-04038 and partially funded by Swedish Research Council Vetenskapsrådet (2019‐03930, 2020‐00457). Acknowledgement. Thanks to fishermen Abdallah Hamisi Juma and Abeid Hamis Juma and hostest Mariam Msami for helping us in field and hosting us as well as Chwaka village, Zanzibar Tanzania.