Experimental study on the performance of the common starfish Asterias rubens subjected to heatwaves of different duration and amplitude (No, Present-day, Extended, Amplified and Amplified & Extended heatwave) followed by a hypoxic upwelling. The study was conducted at GEOMAR, Helmholtz-Centre for Ocean Research Kiel (54.329979 N, 10.148013 E) in the Indoor Benthocosms (Pansch and Hiebenthal 2019) over 63 days from July 10th until September 10th, 2018. The implemented treatments are based on a climatological analysis of a 15-year long data set (Pansch et al. 2018). The temperature was measured over the entire experimental period (TTX 110 type T, Ebro, Ingolstadt, Germany). Salinity, pH, and oxygen concentration were measured along with the simulated upwelling event (Multi 3630 IDS, WTW, Kaiserslautern, Germany). Starfish feeding rate was quantified by measuring the shell length of consumed blue mussels (Dial Caliper DialMax Metric, Wiha Division KWB Switzerland). Based on a previously described relationship between shell size and tissue dry weight for mussels in the study area (Moron et al. 2020), the dry weight of consumed mussels was estimated. Starfish individuals were weighed at the start of the experiment, during the heatwaves, in between heatwaves and the upwelling event, directly after the upwelling event and at the end of the experiment. Starfish activity was measured as righting response (i.e., time needed for the starfish to turn back onto their oral side after being placed on their aboral side) before the beginning of the heatwave treatments, at the end of the heatwaves, before, during and at the end of the upwelling event, and at the end of the experiment.
