Influence of Different Arsenic Species on the Bioavailability and Bioaccumulation of Arsenic by Sargassum horneri C. Agardh: Effects under Different Phosphate Conditions

The growth response and incorporation of As into the Sargassum horneri was evaluated for up to 7 days using either arsenate (As(V)), arsenite (As(III)) or methylarsonate (MMAA(V) and DMAA(V)) at 0, 0.25, 0.5, 1, 2, and 4 mu M with various phosphate (P) levels (0, 2.5, 5 and 10 mu M). Except As(III), algal chlorophyll fluorescence was almost similar and insignificant, regardless of whether different concentrations of P or As(V) or MMAA(V) or DMAA(V) were provided (p > 0.05). As(III) at higher concentrations negatively affected algal growth rate, though concentrations of all As species had significant effects on growth rate (p < 0.01). Growth studies indicated that toxicity and sensitivity of As species to the algae followed the trend: As(III) > As(V) > MMAA(V) similar to DMAA(V). As bioaccumulation was varied significantly depending on the increasing concentrations of all As species and increasing P levels considerably affected As(V) uptake but no other As species uptake (p < 0.01). The algae accumulated As(V) and As(III) more efficiently than MMAA(V) and DMAA(V). At equal concentrations of As (4 mu M) and P (0 mu M), the alga was able to accumulate 638.2 +/- 71.3, 404.1 +/- 70.6, 176.7 +/- 19.6, and 205.6 +/- 33.2 nM g(-1) dry weight of As from As(V), As(III), MMAA(V), and DMAA(V), respectively. The influence of low P levels with increased As(V) concentrations more steeply increased As uptake, but P on other As species did not display similar trends. The algae also showed passive modes for As adsorption of all As species. The maximum adsorption of As (63.7 +/- 6.1 nM g(-1) dry weight) was found due to 4 mu M As(V) exposure, which was 2.5, 7.3, and 6.9 times higher than the adsorption amounts for the same concentration of As(III), MMAA(V), and DMAA(V) exposure, respectively. The bioavailability and accumulation behaviors of As were significantly influenced by P and As species, and this information is essential for As research on marine ecosystems.

Automated summary

This study evaluated the growth response and incorporation of different arsenic species into Sargassum horneri. It was found that arsenite negatively affected algal growth rate, while all arsenic species had significant effects on growth rate. Phosphate levels influenced the uptake of arsenate, but not other arsenic species. The algae accumulated arsenate and arsenite more efficiently than MMAA(V) and DMAA(V). Low phosphate levels had a greater impact on arsenate uptake, while having less effect on other arsenic species. The algae exhibited passive modes of adsorption for all arsenic species. This information is crucial for arsenic research in marine ecosystems.