| Summary: | Understanding and predicting the consequences of ocean acidification for current coral reef communities necessitate high-frequency baseline data. This study presents two months of carbonate chemistry parameters measured in situ every two hours and discrete samples taken at the East Flower Garden Bank in the Northwest Gulf of Mexico. Daily trends of temperature, chlorophyll-a (Chl-a), pH, dissolved oxygen (DO), pressure, and photosynthetically active radiation (PAR) are presented and discussed. Cross-correlations between the parameters’ cycles show their relative timing. Relative Hourly Variability, a composite coefficient of variation, describes the regularity of daily cycles over time. Seasonal changes of aragonite saturation state (Ωvarag), dissolved inorganic carbon, and normalized total alkalinity (nTA) and the aforementioned parameters are compared to historical data from the same site and match well with measurements made at coral reefs of comparable latitude. Typical daily trends of less than 0.75 C, 0.05 pH units, 0.9 mL L^-1 DO, and 0.6 mg m^-3 Chl-a are observed. PAR largely peaks at 10 or noon local time, and the closely correlated DO and pH consistently peak 2-4 hours thereafter. The timing of the temperature cycle is inconsistent. From early May to early July, temperature (3.3 C) and pCOv2 (58 ppm) increase; pH decreases by 0.047 units on the total scale; salinity, nTA, and Ωvarag remain largely unchanged. These trends correlate well with those observed during congruent seasons at HOTS, ESTOC, and BATS (Bates et al. 2014). As a relatively deep and exposed reef, the East Flower Garden Bank is a valuable addition to the existing literature of coral reef carbonate chemistry.
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