Hypoxia tolerance and exercise of an Arctic key stone species the Polar cod Boreogadus saida under global change scenarios

• Main Author: Neven, Carolin J.
• Format: Thesis
• Language: unknown
• Published: University of Bremen 2021
• Subjects: Arctic; Boreogadus saida; Climate change; polar cod
• Online Access: https://epic.awi.de/id/eprint/55224/; https://epic.awi.de/id/eprint/55224/1/MScCJNeven.pdf; https://hdl.handle.net/10013/epic.45b23387-fae2-440a-8712-d5f42a14fab0; https://hdl.handle.net/

The Arctic is the region on Earth expected to experience the highest rate of warming caused by climate change. Ocean warming is directly and indirectly decreasing oxygen concentration in the ocean, therewith confronting marine biota with a change of two crucial abiotic factors. Polar cod Boreogadus saida is an Arctic key stone species due to its central position in the food web. In order to contribute to a better understanding of its upper thermal limits and the synergistic effects of warming and decreasing oxygen availability on its metabolic and swimming capacity, Polar cod were acclimated to a temperature hypothesised to belong to its upper thermal limit (10°C) over 10 months. Using static and swim tunnel respirometry 10°C were found to clearly belong to the pejus temperature range of Polar cod although aerobic scope and swimming capacity were maintained at this temperature. No metabolic compensation was observed for standard metabolic rate that increased by a factor of five. A significant PO2 effect on maximum metabolic rate and aerobic scope was observed when measuring metabolic and swimming capacity at decreasing ambient oxygen levels. Polar cod displayed oxy regulation over the whole PO2 range tolerated. Critical velocity stayed stable until 40% ambient O2 saturation whereas gait transition velocity decreased non-significantly at 50% O2. Temperature had a strong negative effect on hypoxia tolerance by increasing Pcmax and Pcrit to 12.53 and 5.22 kPa O2, respectively. We observed that water masses of 10°C can be tolerated in short-term by Polar cod but do not allow for population survival. Hypoxia tolerance was found to be strongly decreased at the long-term incubation temperature but still remained high in inter-species comparison and with respect to 10°C as pejus temperature. Future research should address hypoxia tolerance of Polar cod during acute warming to understand the physiological impacts during marine heatwaves.