The data were generated during an experiment simulating different frequencies of heatwaves (zero, one and three) in late spring/summer. The experiment was carried out at the Kiel Outdoor Benthocosm (KOB) of GEOMAR Helmholtz Centre for Ocean Research Kiel, located at the Kiel Fjord. The consumers were collected from the mesocosm tanks and the respiration rates were measured in the lab. The measurements were carried out on 10.08.2015 (Idotea balthica), 11.08.2015 (Littorina littorea) and 14.08.2015 (Gammarus sp.). The organisms were kept in gas-tight bottles equipped with sensor spots for non-invasive oxygen measurements, which allowed continuous oxygen logging. Throughout the measurements, the bottles were kept in water baths with temperature set to 19.7 °C, which was the temperature all the KOB tanks were exposed to at the time of the measurements. The oxygen values were converted to carbon and normalized by the area of the tank (1.53 m2) per day.