TY - JOUR
T1 - Cyclic thermal fluctuations can be burden or relief for an ectotherm depending on fluctuations’ average and amplitude
AU - Vajedsamiei, Jahangir
AU - Melzner, Frank
AU - Raatz, Michael
AU - Morón Lugo, Sonia C.
AU - Pansch, Christian
N1 - Funding Information:
The authors acknowledge Claas Hiebenthal, KIMOCC and Ulrike Panknin for providing the culture and technical assistance. They also thank Maral Khosravi for assistance during experiments. This work and J.V. were funded through the Deutsche Forschungsgemeinschaft (DFG) project—The neglected role of environmental fluctuations as a modulator of stress and driver of rapid evolution (Grant Number: PA 2643/2/348431475)—and through GEOMAR. The project was supported by the Cluster of Excellence ‘The Future Ocean’, funded within the framework of the Excellence Initiative by the DFG on behalf of the German federal and state governments. C.P. was funded by the postdoc program of the Helmholtz‐Gemeinschaft Deutscher Forschungszentren and by GEOMAR. Open Access funding enabled and organized by Projekt DEAL. Rhodomonas
Publisher Copyright:
© 2021 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society
PY - 2021/11
Y1 - 2021/11
N2 - Predicting the implications of ongoing ocean climate warming demands a better understanding of how short-term thermal variability impacts marine ectotherms, particularly at beyond-optimal average conditions during summer heatwaves. Using a globally important model species, the blue mussel Mytilus, in a 5-week-long experiment, we (a) assessed growth performance traits under 12 scenarios, consisting of four thermal averages (18.5, 21, 23.5 and 26℃) imposed as constant or daily fluctuating regimes with amplitudes of 2 or 4℃. Additionally, we conducted a short-term assay using different mussel individuals to (b) test for the species capacity for suppression and recovery of metabolic performance traits (feeding and aerobic respiration) when exposed to a 1-day thermal fluctuation regime (16.8–30.5℃). Using this high-resolution data, we (c) generated short-term thermal metabolic performance curves to predict and explain growth responses observed in the long-term experiment. We found that daily high-amplitude thermal cycles (4℃) improved mussel growth when fluctuations were imposed around an extreme average temperature of 26℃, representing end-of-century heatwaves. In contrast, thermal cycles negatively affected mussel growth at a less extreme average temperature of 23.5℃, resembling current peak summer temperature scenarios. These results suggest that fluctuations ameliorate heat stress impacts only at critically high average temperatures. The short-term assay demonstrated that during the warming phase, animals stopped feeding between 24 and 30℃ while gradually suppressing respiration. In the subsequent cooling phase, feeding and respiration partially and fully recovered to pre-heating rates respectively. Furthermore, nonlinear averaging of short-term feeding responses (upscaling) well-predicted longer term growth responses to fluctuations. Our findings suggest that fluctuations can be beneficial to or detrimental for the long-term performance of ectothermic animals, depending on the fluctuations' average and amplitude. Furthermore, the observed effects can be linked to fluctuation-mediated metabolic suppression and recovery. In a general framework, we propose various hypothetical scenarios of fluctuation impacts on ectotherm performance considering inter- or intra-species variability in heat sensitivity. Our research highlights the need for studying metabolic performance in relation to cyclic abiotic fluctuations to advance the understanding of climate change impacts on aquatic systems. A free Plain Language Summary can be found within the Supporting Information of this article.
AB - Predicting the implications of ongoing ocean climate warming demands a better understanding of how short-term thermal variability impacts marine ectotherms, particularly at beyond-optimal average conditions during summer heatwaves. Using a globally important model species, the blue mussel Mytilus, in a 5-week-long experiment, we (a) assessed growth performance traits under 12 scenarios, consisting of four thermal averages (18.5, 21, 23.5 and 26℃) imposed as constant or daily fluctuating regimes with amplitudes of 2 or 4℃. Additionally, we conducted a short-term assay using different mussel individuals to (b) test for the species capacity for suppression and recovery of metabolic performance traits (feeding and aerobic respiration) when exposed to a 1-day thermal fluctuation regime (16.8–30.5℃). Using this high-resolution data, we (c) generated short-term thermal metabolic performance curves to predict and explain growth responses observed in the long-term experiment. We found that daily high-amplitude thermal cycles (4℃) improved mussel growth when fluctuations were imposed around an extreme average temperature of 26℃, representing end-of-century heatwaves. In contrast, thermal cycles negatively affected mussel growth at a less extreme average temperature of 23.5℃, resembling current peak summer temperature scenarios. These results suggest that fluctuations ameliorate heat stress impacts only at critically high average temperatures. The short-term assay demonstrated that during the warming phase, animals stopped feeding between 24 and 30℃ while gradually suppressing respiration. In the subsequent cooling phase, feeding and respiration partially and fully recovered to pre-heating rates respectively. Furthermore, nonlinear averaging of short-term feeding responses (upscaling) well-predicted longer term growth responses to fluctuations. Our findings suggest that fluctuations can be beneficial to or detrimental for the long-term performance of ectothermic animals, depending on the fluctuations' average and amplitude. Furthermore, the observed effects can be linked to fluctuation-mediated metabolic suppression and recovery. In a general framework, we propose various hypothetical scenarios of fluctuation impacts on ectotherm performance considering inter- or intra-species variability in heat sensitivity. Our research highlights the need for studying metabolic performance in relation to cyclic abiotic fluctuations to advance the understanding of climate change impacts on aquatic systems. A free Plain Language Summary can be found within the Supporting Information of this article.
KW - acclimation
KW - Baltic Sea
KW - depression
KW - elasticity
KW - Jensen's Inequality
KW - metabolic suppression
KW - plasticity
KW - stress
UR - http://www.scopus.com/inward/record.url?scp=85111751821&partnerID=8YFLogxK
U2 - 10.1111/1365-2435.13889
DO - 10.1111/1365-2435.13889
M3 - Article
AN - SCOPUS:85111751821
SN - 0269-8463
VL - 35
SP - 2483
EP - 2496
JO - Functional Ecology
JF - Functional Ecology
IS - 11
ER -