Impact of ocean acidification on arctic zooplankton populations

About one third of emitted CO2 is absorbed into the world´s oceans, and the elevated partial pressure of CO2 (pCO2) is now changing the pH of the oceans. This so-called "ocean acidification" (OA) may disturb affected marine populations in ways we cannot y et predict. In this respect, the Arctic constitutes one particular area of concern since the increase in sea water pCO2 is expected to be more pronounced in Polar Regions. Almost all animal studies focus on physiological responses of individuals to eleva ted pCO2. However, the increase in pCO2 will be slow, and major OA effects will only occur on the time scale of several generations, which leaves room for genetic adaptation of populations to the changed environment through natural selection. We intend to investigate how the balance between natural selection and phenotypic plasticity (potential to acclimatize without genetic changes) in traits involved in pH regulation and oxidative stress influences the life history and genetic diversity of arctic copepo d populations during increased pCO2. The gold standard for making predictions of evolutionary change is controlled selection experiments during several generations, and we intend to measure the balance between selection and plasticity through at least 4 g enerations. Copepods will be incubated in small mesocosms and the selection/plasticity balance will be measured by means of reverse transplant tests and molecular determination of genetic diversity.