Identification of lifecycle bottlenecks to assess the vulnerability of fish species to climate change

• Main Author: Dahlke, Flemming
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: atlantic cod; Boreogadus saida; Gadus morhua; Ocean acidification; polar cod
• Online Access: https://epic.awi.de/id/eprint/51200/; https://hdl.handle.net/10013/epic.74496f86-9325-4bbe-8205-2afe27382d92

Globally observed impacts of climate change on marine organisms and ecosystems highlight the need to assess the risks and benefits of international mitigation commitments, such as the goal of limiting global warming to 1.5°C above pre-industrial levels. This requires information on species-specific thermal tolerance thresholds, lifecycle bottlenecks and the sensitivity of critical life stages to additional climate factors such as ocean acidification (OA), the CO2-driven decrease in seawater pH. However, this information is not available for many important fish species, including Atlantic cod (Gadus morhua) and Polar cod (Boreogadus saida). A general assumption is that species adapted to variable climates (e.g., Atlantic cod) have larger tolerance windows than those adapted to relatively stable conditions (e.g., Polar cod), and that egg-stages (embryos) are more vulnerable to temperature changes and OA than adults with fully functional organ systems for oxygen supply and acid-base homeostasis. As adults become sexually mature, temperature windows may narrow due to additional metabolic loads associated with gonad development. Accordingly, there is a risk that future warming and OA will affect the suitability of spawning habitats by exceeding the tolerance thresholds of embryos and/or spawning adults. In this thesis, experimental and meta-analytical investigations on lifecycle bottlenecks were used to describe physiological principles and to identify mitigation pathways that minimize climatic risks regionally (for Atlantic cod and Polar cod) and globally (for marine and freshwater species). The objective of the experimental part (Publication I-III) was to investigate the effects of OA (−0.4 pH, 400 vs 1100 μatm CO2) on embryonic thermal tolerance in Atlantic cod and Polar cod, and to use those embryonic tolerance windows for projections of spawning habitat suitability under different climate change (emission) scenarios. The meta-analysis (Manuscript IV) encompassing data from several hundred species explicitly ...