Realised thermal anomalies
The western Mediterranean Sea experienced marine heatwave conditions
during 2018 summer, coinciding with the translocation experiment.
Maximum daily cool-edge temperatures were 24.9 ºC, 1.3 ºC above long
term summer maximum (averaged 1981-2019). Maximum daily temperatures in
central sites were 29.1ºC, also 1.3 ºC above long term summer maximum
and the second highest temperature on record. Maximum daily temperatures
at P. oceanica’s warm-edge in the eastern Mediterranean were more
typical at 29.3 ºC and 0.18 ºC above long term maximum.
As a result of the marine heatwave in the western Mediterranean, thermal
anomalies experienced by cool-edge and central transplants were similar
in central and warm-edge locations. The highest anomalies were
experienced by cool-centre and cool-warm fragments, which experienced
maximum anomalies of 5.4 ºC and 5.7 ºC above long-term maximum
temperatures in the cool-edge, respectively. Positive thermal stress
anomalies lasted for 130 days for cool-warm fragments and 102 days for
cool-centre fragments over the course of the experiment (Fig. 2, Table
S1). Centre-warm and centre-centre fragments experienced maximum
anomalies of 1.53 ºC and 1.3 ºC, respectively for a duration of 37 and
33 days above long-term summer maxima in P. oceanica’s range
centre. Warm-warm transplants experienced equally high temperatures to
cool-warm and centre-warm transplants, but the smallest relative anomaly
(0.18 ºC for 2 days) above long-term summer maxima. The coolest daily
temperatures recorded throughout the course of the experiment ranged
from 10.5 ºC in the cool-edge, 13.9 ºC in the centre and 16.2 ºC in the
warm-edge.