Laboratory Experiments on Ocean Acidification at IAEA-EL
Nuclear technologies have been used and improved at the IAEA Environment Laboratories for many years to contribute to the global understanding of the marine carbon cycle and the effects of ocean acidification on marine organisms. Changes in calcification (production of calcareous structures such as shells and skeletons) and in growth of different organisms due to ocean acidification, warming and the combination of these factors have been studied. Experiments have focused on reef-building corals because of their ecological value as they host hotspots of biodiversity, and on molluscs, gastropods and cephalopods that have a high economic value. The ß-emitting radionuclide 45Ca can be used to study the calcification process. The high sensitivity of the method makes it particularly useful to study the calcification of small planktonic organisms such as oyster, mussel and sea urchin larvae, expected to be the most vulnerable life stage. It has also been used to study the calcification of pteropods, a key species that is an important food source for high-value fish (e.g. salmon). Nuclear tools have also been useful to investigate metabolic processes under conditions of acidification. The radioisotopes of essential elements (e.g. the radioisotope 65Zn, 57Co, 60Co, 54Mn or 75Se) can be used to assess the effect of ocean acidification on metabolism by studying their accumulation in the organism.
In the future ocean, changes in carbonate chemistry and pH are expected to alter the chemical speciation of trace elements and other chemicals, increasing the concentration of some forms and decreasing others, and therefore modify their availability to marine organisms. In addition, hypercapnia (elevated dissolved CO2 concentration in seawater) will challenge physiological functions that control the vulnerability of animal to chemicals. Radioisotope analysis has provided a valuable tool for tracking and understanding mechanisms of toxicity in marine organisms and for risk assessment of contamination of seafood for human consumption. Such studies have identified contrasting behaviours, depending on the considered contaminant and species, resulting from combined chemical and biological effects caused by climate change and ocean acidification.
In summary, nuclear and isotopic techniques provide important tools to better understand carbon-driven effects on marine organisms and to reduce the uncertainty that exists concerning biological effects of ocean acidification. Current data suggest that the effects of warming together with ocean acidification will be higher than each factor alone for most of the species studied, and have given indications for identifying tolerant organisms that would be key species for adaptation of the ecosystem and the associated services in the future. This kind of information is essential to develop accurate models of effects on fisheries and estimates of the socio-economic impacts of ocean acidification.