Leo, E.

Mark, F. C.

Pörtner, H. O.

Storch, D.

OceanRep

E. Leo, D. Storch. H-O Pörtner, F.C. Mark	Alfred Wegener Institut Helmholtz-Zentrum für Polar-und Meersforschung- www.awi.de – BIOACID Phase II Meeting Kiel 10 – 11 Sept. 2014 Mitochondrial response to OAW in Atlantic cod embryos Consortium 4:  Species interaction at distribution boundaries  WP 4.2:         Mitochondrial and cellular energy budget Introduction: •  Atlantic cod (Gadus morhua) is an economically important fish exploited by both fishery and aquaculture, especially in the North Atlantic and Arctic Oceans. •  Climate changes happen faster in the high latitude oceans with a higher increase of temperature and a steeper decrease in water pH threatening the existence of Atlantic cod in the areas of its maximum exploitation. •  Embryos might be more sensitive to temperature and PCO2 stress because their compensatory systems are not fully developed  Objectives: In this study we looked at the mitochondrial response at the OAW conditions forecasted for the year 2100: •  Effect of temperature on embryonic mitochondria. •  Effect of temperature and CO2 combined. Method:	Atlantic cod broodstock from aquaculture were incubated in the facilities of the National Cod Breeding Centre of Tromsø (Norway) at: §  5°C / 390µatm CO2 (habitat conditions) §  10°C / 390µatm CO2 §  10°C / 1000µatm CO2 (year 2100 conditions)  After 2 months of incubation the animals were stripped, the eggs fertilized in vitro and reared under the same conditions of their parents until gastrulation. At the achievement of the “end of gastrulation” stage: §  Isolation of mitochondria from the whole embryo §  Mitochondrial respiration analysed by high-resolution respirometry §  Each group was analysed both at 5°C and 10°C 	Conclusions: 	•  The high RCR+ of the 10°C / 1000µatm group suggests that the mitochondria are very well coupled, probably as a mechanism to counteract the negative effects of high temperature and PCO2. Therefore, the decrease in OXPHOS of this group could be caused by the action of regulatory-inhibitory systems triggered by the combination of temperature and PCO2 rather than by the degradation of the mitochondrial structure. •  Because of the peculiar role of Complex IV in the Electron Transport System, the decreased capacity of this complex at 10°C might point at the complex as one of the targets of these regulatory-inhibitory systems.    	Oxygraph-O2k, OROBOROS Instruments The Oxydative Phosphorilation capacity (OXPHOS) indicates the maximum activity of the ATP product ion pathway under physiological conditions. In our study the OXPHOS of the 10°C / 1000µatm group is reduced compared to all the other groups at both assay temperatures.	RCR+ is the ratio betwen OXPHOS and the respiration without ATP production induced by chemical inhibition (State IV+). The ratio depicts the coupling ratio of the mitochondria, higher is RCR+ and better coupled the mitochondria are.  Complex IV, or cytochrome c oxidase, is the final electron acceptor of the Electron Transport System, reducing O2 to H2O. In this study the capacity of  Complex IV is lower in both groups incubated at 10°C compared to the control group.  Correspondence: Elettra Leo PhD student Alfred Wegener Institut, Bremerhaven elettra.leo@awi.de 

WP 4.2: Mitochondrial response to OAW in Atlantic cod embryos

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