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Published on: July 10, 2015
Toxicological Effects of Microplastics and Sulfadiazine on the Microalgae Chlamydomonas reinhardtii
Ze Li1,2, Sheng Dong1, Fei Huang1
1Guangdong Provincial Key Laboratory for Plant Epigenetics, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China.
Abstract:
Despite the fact that microplastics (MPs) facilitate the adsorption of environmental organic pollutants and influence their toxicity for organisms, more study is needed on the combination of MPs and antibiotics pollutant effects. In this study, polystyrene MPs (1 and 5 μm) and sulfadiazine (SDZ) were examined separately and in combination on freshwater microalga, Chlamydomonas reinhardtii. The results suggest that both the MPs and SDZ alone and in combination inhibited the growth of microalgae with an increasing concentration of MPs and SDZ (5-200 mg l-1); however, the inhibition rate was reduced by combination. Upon exposure for 7 days, both the MPs and SDZ inhibited algal growth, reduced chlorophyll content, and enhanced superoxide dismutase (SOD) activities, whereas glutathione peroxidase (GSH-Px) activity was elevated only with the exposure of 1 μm MPs. Fluorescence microscopy and scanning electron microscopy also indicated that particle size contributed to the combined toxicity by aggregating MPs with periphery pollutants. Further, the amount of extracellular secretory protein increased in the presence of MPs and SDZ removal ratio decreased when MPs and SDZ coexisted, suggesting that MPs affected SDZ metabolism by microalgae. The particle size of microplastics affected the toxicity of MPs on microalgae and the combined effect of MPs and SDZ could be mitigated by MPs adsorption. These findings provide insight into microalgae responses to the combination of MPs and antibiotics in water ecosystems.
Insights
Microplastics and the antibiotic sulfadiazine inhibit microalgae growth. However, microplastic adsorption mitigates combined toxicity, revealing complex interactions in aquatic ecosystems.
Area of Science:
- Environmental Science
- Ecotoxicology
- Aquatic Biology
Background:
- Microplastics (MPs) adsorb pollutants, affecting organism toxicity.
- Combined effects of MPs and antibiotics on aquatic life require further investigation.
Purpose of the Study:
- To investigate the individual and combined effects of polystyrene MPs (1 and 5 μm) and sulfadiazine (SDZ) on the freshwater microalga *Chlamydomonas reinhardtii*.
- To understand the role of MP particle size in combined toxicity and pollutant interactions.
Main Methods:
- Exposure of *C. reinhardtii* to varying concentrations of MPs and SDZ, individually and in combination.
- Assessment of algal growth, chlorophyll content, and enzyme activities (SOD, GSH-Px).
- Microscopic analysis (fluorescence and scanning electron microscopy) and measurement of extracellular secretory proteins.
Main Results:
- Both MPs and SDZ inhibited algal growth, reduced chlorophyll, and increased SOD activity.
- Combined exposure showed reduced inhibition rates compared to individual exposures, suggesting mitigation.
- MP particle size influenced toxicity and aggregation with pollutants; MP adsorption decreased SDZ removal by algae.
Conclusions:
- Microalgae growth and physiological responses are negatively impacted by MPs and SDZ.
- MP adsorption can mitigate the combined toxicity of MPs and antibiotics.
- MP particle size is a critical factor in the ecotoxicological effects of combined pollutants on microalgae.
