105. Behaviour of Atlantic cod (Gadus morhua) is more resilient to ocean warming and acidification than that of Polar cod (Boreogadus saida)

Matthias Schmidt (1), Hans-Otto Pörtner (1), Christian Bock (1)*, Daniela Storch (1)

1 Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany

Background
Ocean acidification (OA) as projected for the year 2100 strongly alters the behaviour of tropical and temperate marine teleost and elasmobranch species with potential impacts for individual fitness and impacts at the ecosystem level. We investigated whether OA changes behavioural laterality and spontaneous activity of two co-occurring cold-water adapted teleost species from Svalbard, Polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua). We further tested for effects of temperature, as the Arctic Ocean will warm in parallel to the acidification process.

Methods
B. saida and G. morhua were incubated for 6 weeks at 2 different CO2 concentrations (current day and as projected for the year 2100) and at 4 different temperatures specific for their thermal window (0,3,6,8°C for B. saida and 3,8,12,16°C for G. morhua, respectively). Behavioural laterality of animals was tested using a Detour test and spontaneous activity was quantified through estimation of crossed grid-lines over a defined period of time.

Findings
OA significantly affected behavioural laterality of B. saida but not that of G. morhua. Spontaneous activity of B. saida, but not of G. morhua was significantly dependent on environmental temperature. Interactive effects of ocean acidification and temperature were not detected.

Conclusions
The behaviour of B. saida may be more vulnerable in a more acidified, warmer future ocean than the behaviour of G. morhua. Due to ocean warming, G morhua currently moves northward into the distribution area of B. saida with potential for competition. Behavioural resilience of G. morhua to future OA scenarios indicates that this invading species might out-compete native B. saida in those areas where the two species will co-exist.