Po uptake in microalgae at different seawater pH: An experimental study simulating ocean acidification

摘要

Climate change effects such as ocean acidification (OA) are known to affect the trace metal distribution. This experimental study provides the first data on Po-209 uptake rates and Po-210 concentration in five microalgae species under different pH scenarios. The experiment was conducted in replicates at three pH conditions 8.2, 8.0, and 7.5, representing the current and future climate change scenario as per IPCC RCP8.5. The Po-209 uptake in the phytoplankton was highest in Thalassiosira weissflogi, i.e. 83% of the Po-209 tracer was taken up at 8.2 pH whereas the lowest uptake was observed in Dunaliella sauna equivalent to 20% at 7.5 pH. Similar behavior was observed in Po-210 concentrations in these microalgae, where Po-210 ranged between 3.16 +/- 0.03 and 11.6 +/- 0.04 Bq kg(-1) wet weight (ww), with the highest in the Thalassioria weissflogi at 8.2 pH, and the lowest in Dunaliella salina at 7.5 pH. The difference in Po-209 uptake and Po-210 concentration was statistically significant (p < 0.001) both among species and the pH treatments in the order: Thalassiosira weissflogi > Tetraselmis suecica > Chaetoceros muelleri > Isochtysis galbana > Dunaliella salina and 8.2 > 8.0 > 7.5. A higher concentration of Po-209 in seawater was measured at low pH condition in all the experimental tanks. Though the data clearly show the difference in concentration and uptake of polonium at different pH conditions, it is not known if lower pH is affecting the adsorbed or absorbed fraction. A detailed investigation will be required to understand the process as it can have a significant effect on biomagnification and marine food chain transfer under changing climatic scenarios.