Ocean Acidification in the Arctic – challenges and knowledge gaps

Abstract

Ocean Acidification (OA) is the term used to describe the effect of oceanic uptake of anthropogenic CO2 primarily caused by the burning of fossil fuels. This has resulted in decreased pH and carbonate ion concentrations [CO32-]. Lower pH leads to a decrease in carbonate concentration and changes in the calcification process, which may have negative impacts on calcifying organisms, such as primary producers, zooplankton (e.g. pteropods and crustaceans) and cold water corals. The cold and relatively fresh waters at high latitudes promote CO2 solubility, and calcium carbonate dissolution, which makes these waters particularly vulnerable for OA impact. The Arctic Ocean is predicted to be the first to become undersaturated with respect to aragonite, which is the most labile form of calcium carbonate, hence aragonite-forming organisms such as pteropods may be particularly at risk.

Information on biological effects in the Arctic is beginning to emerge from individual studies and experiments, but only a small number of Arctic species has been studied, usually over very short periods. Long-term effects on single taxa and their life cycles, as well as impacts on food web structure are largely unknown. Furthermore, other stressors, such as warming and freshening of the ocean surface, and indirect effects of OA will likely affect Arctic marine organisms. Thus, OA has to be put into the context of global change, especially in the Arctic, where these other changes are also drastic and occurring simultaneously. Perturbations at the base of the marine food web will ultimately also affect intermediate trophic levels such as fish, which in turn may also suffer from direct effects of OA on their reproduction and larval survival. There is still a need to identify the most sensitive life stages of marine invertebrates and fish. Genetic plasticity and adaptation will also play a role in determining which effects OA might cause in a future Arctic Ocean, and to date this is highly unknown.

Maria Fossheim
Institute of Marine Research, flagship program leader, Ocean Acidification and ecosystems effect in Northern waters, FRAM – High North Research Centre for Climate and the Environment, Tromsø, Norway

 

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