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Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum
Chao Liu1,2, Jiangbing Qiu1,2, Zhixuan Tang1,2
1College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
Abstract:
Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L-1, 25 mg L-1 and 100 mg L-1) on the growth, chlorophyll a (Chl a), photosynthetic activity (Fv/Fm) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L-1) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator Fv/Fm of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L-1 had no significant effect on cell toxin quota, and the high concentration 100 mg L-1 significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, Fv/Fm and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.
Insights
Microplastics (MPs) significantly inhibit the growth of toxic algae Alexandrium pacificum at high concentrations, while promoting toxin production. MP effects depend on size and concentration, impacting algal health and PST biosynthesis.
Area of Science:
- Environmental Science
- Marine Biology
- Ecotoxicology
Background:
- Microplastics (MP) are pervasive pollutants in aquatic ecosystems.
- The impact of MPs on toxigenic algae, particularly those producing paralytic shellfish toxins (PST), remains largely unknown.
- Understanding these interactions is crucial for assessing ecological risks.
Purpose of the Study:
- To investigate the effects of different sizes and concentrations of polystyrene MPs on the growth, physiology, and PST production of the toxic dinoflagellate Alexandrium pacificum.
- To determine if MP shading influences algal responses.
- To provide insights into the ecological consequences of MP pollution on harmful algal blooms.
Main Methods:
- Exposure of Alexandrium pacificum ATHK to 1 μm and 0.1 μm polystyrene MPs at concentrations of 5, 25, and 100 mg L⁻¹.
- Monitoring of algal growth, chlorophyll a content, and photosynthetic efficiency (Fv/Fm).
- Quantification of PST production and analysis of toxin profiles.
Main Results:
- High MP concentrations (100 mg L⁻¹) significantly inhibited algal growth, with effects varying by MP size and concentration.
- Chlorophyll a content generally increased post-MP exposure.
- Photosynthetic activity (Fv/Fm) showed initial inhibition followed by recovery or further inhibition depending on MP treatment.
- PST biosynthesis was significantly promoted at high MP concentrations (100 mg L⁻¹), though overall toxin content at day 21 was not significantly different.
- MP shading did not affect algal growth, chlorophyll a, photosynthetic activity, or toxin production.
Conclusions:
- Microplastics, particularly at high concentrations, can negatively impact the growth of PST-producing algae like Alexandrium pacificum.
- MPs can modulate toxin production, potentially altering the ecological risk of harmful algal blooms.
- The findings highlight the complex interactions between microplastic pollution and marine phytoplankton.
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