Description: Robust estimates of marine species vulnerability to ongoing climate change require realistic stressor experiments. Here, we subjected an important coastal predator, the sea star Asterias rubens, to projected warming and ocean acidification over an annual seasonal cycle. Warming and, less so, acidification, had strongly season-specific impacts on animal energy budgets. Specifically, simulated future summer temperatures caused 〉95% sea star mortality, reduced feeding rate and body mass loss. Additional acute experiments demonstrated that respiratory oxygen flux was preferentially directed to support high summer metabolism at the expense of feeding-related processes. Using 15 years of field temperature data and end of century warming projections, we estimate that potentially lethal summer heat waves will occur in 20% of future years. Our study demonstrates the importance of assessing stress responses along seasonal thermal cycles and the high selective force that future summer heat waves likely can exert on coastal marine animal populations.

Description: Robust estimates of marine species vulnerability to ongoing climate change require realistic stressor experiments. Here, we subjected an important coastal predator, the sea star Asterias rubens, to projected warming and ocean acidification over an annual seasonal cycle. Warming and, less so, acidification, had strongly season-specific impacts on animal energy budgets. Specifically, simulated future summer temperatures caused 〉95% sea star mortality, reduced feeding rate and body mass loss. Additional acute experiments demonstrated that respiratory oxygen flux was preferentially directed to support high summer metabolism at the expense of feeding-related processes. Using 15 years of field temperature data and end of century warming projections, we estimate that potentially lethal summer heat waves will occur in 20% of future years. Our study demonstrates the importance of assessing stress responses along seasonal thermal cycles and the high selective force that future summer heat waves likely can exert on coastal marine animal populations.

Description: Data from 1997-2018 were logged every 8 minutes in the Inner Kiel Fjord (54°19'46.0"N; 10°08'58.3"E) in shallow waters (Hydrometeorological station: Fa. Driesen und Kern, Bad Bramstedt). Until 2013 the sensor was deployed floating at the surface, but due to settlements on the floating device, the actual depth is not perfectly certain. Therefore, in 2013 the sensor was mounted to a fixed depth of 1.8 m (below sealevel). If a value differed more than 1.0°C from the preceding and following value, the value was interpolated between the two adjacent values. If values were 2) constant for more than 4 hours, 2) missing within ± 8 min, and if 3) changes in values exceeded 0.7°C within 16 min, the values were set to NA. This holds true for the following times: 1999-05-21 21:20 - 1999-06-17 15:00, 2000-11-10 12:00 - 2000-11-18 10:00, 2001-01-06 12:20 - 2001-01-08 07:40, 2014-08-30 18:00 - 2014-09-19 16:20, 2015-01-07 14:40 - 2015-02-23 20:00, 2016-11-09 03:20 - 2016-12-04 03:20 - 2017-01-24 23:25 - 2017-01-25 12:00. Gaps larger than 3 days were filled with data (if available) obtained from sensors very close to the actual measuring site (SeapHOx, Scripps Research Institute San Diego 1m; or Hydrometeorological station, Fa. Driesen und Kern, Bad Bramstedt 1.5m): 2000-11-11 - 2000-11-17 (Hydrometeorological station), 2001-08-03 - 2001-08-28 (Hydrometeorological station), 2005-10-07 - 2005-10-17 (Hydrometeorological station), 2006-02-09 - 2006-02-22 (Hydrometeorological station), 2014-08-29 - 2014-09-18 (Hydrometeorological station), 2015-01-08 - 2015-02-24 (Hydrometeorological station), 2016-03-10 - 2016-03-13 (SeapHOx), 2016-06-03 - 2016-06-15 (SeapHOx), 2016-11-10 - 2016-12-05 (SeapHOx). Data from 1.5 m water depth were corrected by subtracting a systematic deviance of 0.3°C.