A novel low-cost, high-precision sea temperature sensor for coral reef monitoring

The role of elevated sea temperatures in coral bleaching has been well documented. Many of the sea temperature records utilized for purposes of widespread, multi-species bleaching predictions in recent publications have been acquired through satellite remote sensing. Satellites estimate sea temperatures at only a narrow range of depths near the surface of the ocean and may therefore not adequately represent the true temperatures endured by the world's coral ecosystems. To better characterize sea temperature regimes that coral reef ecosystems experience, as well as better define the individual thresholds for each species that bleaches, in situ sea temperature sensors are required. Commercial sensors are expensive in large quantities, however, reducing the capacity to conduct large- scale research programs to elucidate the range of significant scales of temperature variability. At the National Oceanic and Atmospheric Administration's (NOAA) Atlantic Oceanographic and Meteorological Laboratory (AOML), we designed a low-cost (roughly US$9 in parts) and high- precision sea temperature sensor that uses an Arduino microprocessor board and a high accuracy thermistor. This new temperature sensor autonomously records temperatures onto a memory chip and provides better accuracy (+0.05 °C) than a comparable commercial sensor (+0.2 °C). Moreover, it is not difficult to build; anyone who knows how to solder can build the temperature sensor. In March 2019, students at middle and high schools in Broward County, Florida, built close to 60 temperature sensors. During 2019, these sensors will be deployed by Reef Check, a global-scale coral reef monitoring organization, as well as by other programs to determine worldwide sea temperature regimes through the Opuhala Project (https://www. coral. noaa. gov/opuhala). This paper chronicles results from the initial proof-of-concept deployments for these AOML-designed sensors.