Interaction Effects of Ocean Acidification and Warming on the Marine Copepod Calanus finmarchicus
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- Institutt for biologi 
Ocean acidification and concurring warming of the oceans poses an ongoing threat to marine organisms, but little is known about their combined effects. The boreal calanoid copepod Calanus finmarchicus is a key stone species in North Atlantic Ocean and adverse effects of concurring OA and warming could have major impacts for ecosystem structure and function. A 2x2 cross factorial experiment with two levels of CO2-concentration (390 (ambient) and 2080ppm (acidified)), and two levels of temperature (11°C (ambient) and 14°C (warming)) were set up to study possible interactive (synergistic/ antagonistic) effects between these two factors. The results show that interactions between the two stressors induced a positive synergistic effect on the development rate (only significant at the C1-stage). Also, a significant reduction in dry weight (1,24 fold) and lipid content (1,56 fold) in animals exposed to warming and acidification combined, suggests that C. finmarchicus could be sensitive towards ocean acidification predicted to occur by year 2300, in combination with increasing temperature. However, acidification also displays an antagonistic effect by reducing the negative effect of warming on the dry weight and lipid content of the animals. The complex interactions induced by combining warming and acidification highlight the importance of looking at multiple environmental factors simultaneously, as this approach might reveal biological responses previously unsuspected.