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

Area of Science:

• Marine Biology
• Environmental Chemistry
• Oceanography

Background:

• Ocean acidification (OA), a consequence of climate change, alters marine trace metal distribution.
• Polonium (Po) is a naturally occurring radioactive element with implications for marine ecosystems.
• Understanding Po dynamics in microalgae is crucial for assessing marine food web impacts.

Purpose of the Study:

• To investigate the uptake rates of polonium-209 (²⁰⁹Po) and concentrations of polonium-210 (²¹⁰Po) in five microalgae species.
• To assess the influence of different pH levels, simulating current and future climate change scenarios, on polonium dynamics.
• To provide the first experimental data on polonium uptake and concentration in microalgae under varying pH conditions.

Main Methods:

• Experimental study conducted with five microalgae species at three pH levels: 8.2, 8.0, and 7.5.
• Replicate experiments were performed to measure ²⁰⁹Po uptake rates and ²¹⁰Po concentrations.
• Statistical analysis was used to determine the significance of differences among species and pH treatments.

Main Results:

• ²⁰⁹Po uptake was highest in Thalassiosira weissflogi (83% at pH 8.2) and lowest in Dunaliella salina (20% at pH 7.5).
• ²¹⁰Po concentrations ranged from 3.16 ± 0.03 to 11.6 ± 0.04 Bq kg⁻¹ ww, with highest levels in T. weissflogi at pH 8.2 and lowest in D. salina at pH 7.5.
• Significant differences (p < 0.001) in ²⁰⁹Po uptake and ²¹⁰Po concentration were observed among species and pH treatments, following the order: T. weissflogi > T. suecica > C. muelleri > I. galbana > D. salina and pH 8.2 > 8.0 > 7.5.

Conclusions:

• Microalgae species exhibit varying capacities for polonium uptake and concentration, influenced by pH.
• Lower pH conditions correlated with higher seawater ²⁰⁹Po concentrations.
• Further investigation is required to differentiate between adsorbed and absorbed polonium fractions and their impact on marine food chain transfer under climate change.