The Pacific oyster Crassostrea gigas is a sessile marine bivalve inhabiting the highly dynamic and stressful intertidal zone, one of the most variable and unpredictable environments on Earth, increasingly affected by global changes. Until now, no data existed on endogenous pH, oxygen, or temperature in intertidal bivalves in their natural environment. However, limited biological data on body temperature have been collected in some intertidal species using mimetic shells equipped with data loggers (without the living animal) or through infrared measurements (Helmuth, 1998; Helmuth and Hofmann, 2001; Helmuth et al. 2002, 2016; Denny et al., 2011). These methods provide strong insights on intertidal thermal stress but lack real-time physiological data from alive animals. 

The Phoxy© probe, developed by Ifremer, was designed to monitor all together the temperature, pH, and oxygen levels within living C. gigas oysters. Its specifications were collaboratively developed by biologists, mechanical, and electronic engineers. In August 2018, a two-year-old hatchery-produced oyster was equipped with the Phoxy© probe and deployed in the intertidal zone at the Bay of Brest experimental site (Brittany, France, 48° 20′ 06.19″ N, 4° 19′ 06.37″ W) as part of the Ifremer’s Ecoscopa project. The oyster was positioned at a bathymetric depth of 3 meters, corresponding to the middle range of the natural distribution of wild C. gigas in the field (Petton et al., 2020 ; Corporeau et al., 2022, Dupoue et al., 2023). The Phoxy© probe recorded data at a frequency of one measurement per minute.