Figure 1.

Transformation of inorganic C-14 to OBC-14 enabling accumulation and trophic transfer of C-14 in aquatic organisms. (a) Internalization percentage of dosed C-14 by algae. The gray dashed line represents the 100% of C-14 that was bio-utilized by algae. (b) Accumulation of C-14 in S. obliquus under cultivation in different medium containing NaHCO₃ (AF) or not (SE) at a concentration of 15 bq mL⁻¹. (c) The elimination of C-14 from algae under various culture media including AF, SE and AF containing 10 mg L⁻¹ NOM. (d) Uptake of C-14 by D. magna through direct exposure to DIC-14 solution with a concentration of 5 bq mL⁻¹ and trophic transfer from C-14-accumulated algae with a nominal concentration of 5 bq mL⁻¹. (e) The elimination of C-14 from D. magna under various culture media including AF, NOM solution and AF containing 1 × 10⁶ cells/L algae. (f) Intrinsic percentage of carbon in carbohydrates, proteins and lipids of algae and daphnia (the outer circle) vs. the percentage of OBC-14 in carbohydrates, proteins and lipids in a corresponding organism after elimination (the inner circle). Data points are average values of three replicates; error bars indicate standard deviation. Asterisks (*) or NS indicate statistically significant (*P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001) or insignificant differences.