Diel and seasonal variability of pCO2 and oxygen by high-frequency monitoring in tropical urban coastal waters (Guanabara bay, Brazil) during 2018-2020

High-frequency monitoring approach to measure continuously surface water pCO2 and dissolved oxygen (DO) during diel (24-h) and seasonal in monthly campaigns between June 2018 and January 2020 in tropical urban coastal waters (Guanabara Bay, Brazil; -22.84° S -43.22° W). Water samples were also collected each 2-hour to measure temperature, practical salinity, pH, chlorophyll-a, total phosphorus and nitrogen, and total alkalinity. CO2 flux, pCO2 (saturation%) and oxygen saturation were calculated from pCO2 and dissolved oxygen measurements, respectively.