Underwater temperature on off-shore coral reefs of the Florida Keys, U.S.A. (Version 9)

Temperature data were recorded with Onset® HOBO® Water Temp Pro V2 (U22-001) data loggers, in duplicate, at each site. The data-logger manufacturer (Onset Brands, Bourne, MA, U.S.A.) reports accuracy: ±0.21°Celsius (C) from 0° to 50°C (±0.38°Fahrenheit [F] from 32° to 122°F). In 2021, a temperature-accuracy check was added to the logger-launch protocol using a 0°C-degree ice-bath as described on the Onset website (https://www.onsetcomp.com/resources/tech-notes/quick-temp-accuracy-check-ice-bath). In doing so, no loggers have been found outside of the reported specifications. Loggers were attached to concrete blocks fixed to the reef with stainless-steel rods and epoxy at depths of 7 to 16 feet (ft) of seawater. The 15-minute interval temperature data reported are the means of two loggers approximately 30 to 50 feet apart and within 1 to 3 feet in depth from one another. All loggers were placed at the same height above the substratum (approximately 2 to 4 inches). Every six months, using a self-contained underwater breathing apparatus (SCUBA), new loggers were carried underwater by divers at the USGS and swapped with the old loggers such that there was always an overlapping time segment when all four loggers were underwater (also known as, "hot-swapped"). In rare cases when one logger was lost or damaged during deployment, the temperature from a single logger is reported. There is a short gap in the dataset for Fowey Rocks (five data points on May 4, 2010, between 10:45 and 11:45), due to logger programming issues, and a long gap, also at Fowey Rocks (October 14, 2021, to May 21, 2023) due to loss of both loggers. Measurements at now discontinued sites were made at Molasses Reef from April 2009 to April 2013, at Crocker Reef from June 2013 to August 2022, and at Sombrero Reef from July 2009 to August 2022. Data collection continues at three sites in the Dry Tortugas National Park (Pulaski West, Pulaski Light and Garden Key) and four sites in Biscayne National Park (Ball Buoy North, Shadow Reef, Brewster Reef, and Fowey Rocks), and the data release will continue to be updated.