New encounters in Arctic waters: a comparison of metabolism and performance of polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua) under ocean acidification and warming

Abstract

Oceans are experiencing increasing acidification in parallel to a distinct warming trend in consequence of ongoing climate change. Rising seawater temperatures are mediating a northward shift in distribution of Atlantic cod (Gadus morhua), into the habitat of polar cod (Boreogadus saida), that is associated with retreating cold water masses. This study investigates the competitive strength of the co-occurring gadoids under ocean acidification and warming (OAW) scenarios. Therefore, we incubated specimens of both species in individual tanks for 4 months, under different control and projected temperatures (polar cod: 0, 3, 6, 8°C, Atlantic cod: 3, 8, 12, 16°C) and PCO 2 conditions (390 and 1170 latm) and monitored growth, feed consumption and standard metabolic rate. Our results revealed distinct temperature effects on both species. While hypercapnia by itself had no effect, combined drivers caused nonsignificant trends. The feed conversion efficiency of normocapnic polar cod was highest at 0°C, while optimum growth performance was attained at 6°C; the long-term upper thermal tolerance limit was reached at 8°C. OAW caused only slight impairments in growth performance. Under normocapnic conditions, Atlantic cod consumed progressively increasing amounts of feed than individuals under hypercapnia despite maintaining similar growth rates during warming. The low feed conversion -016-1932-z efficiency at 3°C may relate to the lower thermal limit of Atlantic cod. In conclusion, Atlantic cod displayed increased performance in the warming Arctic such that the competitive strength of polar cod is expected to decrease under future OAW conditions.

Impacts of the Changing Ocean-Sea Ice System on the Key Forage Fish Arctic Cod (Boreogadus Saida) and Subsistence Fisheries in the Western Canadian Arctic—Evaluating Linked Climate, Ecosystem and Economic (CEE) Models

“…Only few laboratory-based thermal tolerance studies of Arctic cod exist and even fewer quantify the impact of multistressors (Kunz et al, 2016(Kunz et al, , 2018Leo et al, 2017). Table 1 indicates the known physiological limits for Arctic cod and capelin, in comparison.…”

Acclimation potential of Arctic cod (Boreogadus saida Lepechin) from the rapidly warming Arctic Ocean

“…Nevertheless, our understanding of the thermal physiology of B. saida remains far from complete. Notably, studies of oxygen uptake are limited to measurements of routine metabolic rate (RMR) between −1.5 and 6.0°C (Holeton, 1974;Steffensen et al, 1994;Hop and Graham, 1995;Kunz et al, 2016). Based on temperature and holding duration for B. saida, these studies have produced remarkably similar values of oxygen uptake.…”

Impact of ocean warming and acidification on the behaviour of two co-occurring gadid species, Boreogadus saida and Gadus morhua, from Svalbard

“…Animals were transferred into individual tanks (height: 35 cm, diameter: 30 cm, volume: ~24 l with a flow-through of ~500 ml min −1 ) and randomly distributed among treatment groups. The animals were kept separately in order to enable quantification of feed consumption of each individual, which was published separately (Kunz et al 2016). Water supply occurred through a re-circulating aquarium system with a total volume of 10 m 3 .…”