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Beyond acute toxicity: How nanoplastics and norfloxacin jointly trigger cyanobacterial blooms by modulating lag-phase metabolism
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Researchers exposed a freshwater algae species to low doses of an antibiotic and tiny plastic particles, alone and together, during different growth stages in lab tests. Algae exposed to both pollutants during early growth stages showed enhanced growth and changes in how they processed nitrogen, while the same exposure during later growth stages caused stress and slowed growth. The findings suggest that traditional lab tests using high pollutant doses may miss how low levels of multiple contaminants together trigger algal blooms in nature.
Existing research on pollutant-induced algal blooms has primarily focused on high-concentration exposures during the logarithmic growth phase, largely overlooking the lag phase, a critical window for bloom initiation, under combined exposure at environmentally relevant levels. This study investigates the physiological and metabolic responses of Microcystis aeruginosa during the lag and logarithmic phases following exposure to environmentally relevant concentrations of norfloxacin (NOR), alone and in combination with carboxyl-modified polystyrene nanoplastics (PS-NPs). Our results demonstrate that PS-NPs significantly enhance the growth-promoting effect of low-dose NOR during the lag phase in a growth-stage-dependent manner, with these early-stage cells exhibiting more pronounced responses and subtle nitrogen metabolism disturbances, while logarithmic-phase cells showed only weak physiological changes. PS-NPs further amplified these stage-specific differences. Exposure to the combined L-NOR-NP treatment during the lag phase was associated with moderate antioxidant responses and did not induce significant membrane lipid peroxidation, while photosynthetic efficiency was sustained, facilitating toxin accumulation, and induced a distinct metabolic pattern characterized by stable carbon flux and selective nitrogen activation, in stark contrast to the general suppression of both carbon and nitrogen metabolism observed under high-concentration exposures. In contrast, L-NOR-NP exposure during the logarithmic phase induced oxidative stress and inhibited carbon metabolism, resulting in insufficient energy supply and limited growth promotion. These findings suggest that traditional high-concentration exposure paradigms may underestimate the ecological risks of emerging contaminants, and that lag-phase metabolic activation, characterized by stable carbon flux and selective nitrogen activation, could serve as a potential early-warning biomarker for cyanobacterial blooms.
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Unraveling individual and combined toxicity of nano/microplastics and ciprofloxacin to Synechocystis sp. at the cellular and molecular levels
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Researchers studied the individual and combined toxic effects of nano- and microplastics with the antibiotic ciprofloxacin on a freshwater cyanobacterium. They found that while each pollutant caused harm on its own, the antibiotic actually showed an antagonistic interaction with the plastic particles, reducing some of their combined toxicity. The study provides important insights into how microplastics and pharmaceutical pollutants interact in aquatic environments, which may complicate pollution risk assessments.
Higher toxicity induced by co-exposure of polystyrene microplastics and chloramphenicol to Microcystis aeruginosa: Experimental study and molecular dynamics simulation
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Researchers studied what happens when the antibiotic chloramphenicol and polystyrene microplastics are present together in water containing blue-green algae. The study found that the combined exposure was more toxic to the algae than either pollutant alone, disrupting photosynthesis and gene expression. The findings suggest that microplastics and antibiotics may interact in ways that amplify their harmful effects on aquatic ecosystems.
Single and combined effects of microplastics and lead on the freshwater algae Microcystis aeruginosa
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Researchers tested the individual and combined effects of microplastics and lead (Pb) on the growth, photosynthetic pigments, and antioxidant responses of the freshwater cyanobacterium Microcystis aeruginosa. They found that microplastics alone inhibited growth while low-dose Pb promoted it, but their combination altered toxicity outcomes in complex ways depending on concentration, indicating that co-exposure risks in freshwater cannot be predicted from single-contaminant studies.
Inhibition mechanisms of nanoplastics and ofloxacin on marine Synechococcus: Evidence from coupled physiological and transcriptomic assessments
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Researchers exposed marine cyanobacteria (Synechococcus) to nanoplastics and an antibiotic, alone and combined, in a lab setting. While population growth showed less harm than expected when combined, cell-level tests showed worse damage: membrane breakdown, oxidative stress, and shutdown of photosynthesis and energy production genes.
Microplastics and co-pollutant with ciprofloxacin affect interactions between free-floating macrophytes
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Researchers found that polyethylene microplastics and ciprofloxacin co-pollutants altered competitive interactions between free-floating macrophytes, with combined exposure affecting plant growth and physiological responses differently than individual pollutant exposure.
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