Future climate change and marine heatwaves - Projected impact on key habitats for herring reproduction

• Published in: The Science of the total environment Vol. 951; p. 175756
• Main Authors: Gröger, Matthias, Börgel, Florian, Karsten, Sven, Meier, H.E. Markus, Safonova, Kseniia, Dutheil, Cyril, Receveur, Aurore, Polte, Patrick
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2024
• Subjects: Climate change; Fish habitats; Marine heatwaves; Regional climate impact; Climate change; Regional climate impact; Marine heatwaves; Fish habitats
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.175756

This study explores the impact of global climate targets on sea surface temperatures and marine heatwaves (MHWs) in the Baltic Sea. We further evaluate potential adverse climate effects on the reproductive success of the western Baltic Sea (WBS) herring stock, which underwent a dramatic decline during the past two decades. For this, we use refined ensemble climate projections from the Coupled Model Intercomparison Project. For the WBS herring spawning ground, the number of MHW days nearly triples from 34 days/year in the historical period, to 102 days/year already under the optimistic 1.5 °C target of global climate warming (Paris, 2015) and further increases at a rate of 36 to 48 [days yr−1]/0.5 °C beyond the 1.5 °C target. The average MHW surface extent more than doubles in the 1.5 °C target from ~8 % to 21 % in this area. This study finds the phenological winter climate considerably altered in response to future global warming and more frequent MHW days in the WBS. The winter duration reduces by ~25 % already in the 2.0 °C target but by ~60 % in the 4.0 °C target compared to the historical climate. Winter inceptions/terminations occur successively later/earlier and the share of missed winters, i.e. winters unsuitable to support herring reproductive success, increases by up to ~70 %. Days with heat stress on the cardiac function of herring larvae will likewise increase and occur earlier in the year. Consequently, the early life cycle of herring will face more often winter conditions that were unprecedented during the historical past, and the risk for future reproductive failure will increase. However, our results reveal that abiotic disturbances for the marine ecosystem can be partly mitigated if global warming remains compliant with the 1.5 °C target. [Display omitted] •The number of MHW days ~triples under the 1.5 °C global target and further increases at a rate of 36 to 48 days yr-1/0.5°C beyond the 1.5 °C target•Phenological winter duration is reduced by ~25% even in the 2.0°C target but reduces up to ~60% in the 4.0°C scenario compared to the historical climate and more winters miss completely•Herring larvae will face more frequent days with heat stress inducing cardiac dysfunctions•Abiotic disturbances for the Baltic Sea marine ecosystem can be at least partly mitigated if global warming remains below or compliant with the 1.5°C target