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Extracellular polymeric substance mediating nanoplastics-promoted short-term Porphyridium growth disrupts marine carbon and phosphorus migration
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This study found that nanoplastics can initially boost the growth of a marine red algae species by reducing oxidative stress and enhancing light absorption. However, this short-term benefit came at a long-term cost, as the nanoplastics disrupted carbon and phosphorus cycling in the water and eventually led to nutrient deficiency for the algae. The findings reveal that even when nanoplastics appear harmless in the short term, they can fundamentally alter important marine nutrient cycles.
The ecotoxicity of nanoplastics (NPs) on marine microalgae has been extensively explored recently, yet the mechanisms driving short-term growth improvement caused by NPs remain poorly understood. In the present study, we observed that a relatively high concentration (10 mg/L) of the green fluorescently labeled fresh polyamide-polymethyl methacrylate polymer blend (w/w 21:4) NPs beads (200 nm) significantly enhanced the cell density of Porphyridium cruentum (42.1 %) by alleviating reactive oxygen species generation, chlorophyll degradation, and photoinhibition. An increase in the sticky bounded exopolysaccharides (b-EPs) surrounding P. cruentum surface enhanced NP adsorption within five hours of exposure, with -CH bond in phospholipids/glycolipids and polysaccharides of b-EPs supporting the adsorption to mitigate photoinhibition. Increased free exopolysaccharides (EPs) removed inorganic and organic carbon and 48 % of dissolved organic matter (DOM), encapsulating NPs into sediments while cooperating with pH elevation. However, short-term growth promotion resulted in cell shading and phosphorous deficiency after 12 days of cultivation. Consequently, the photosynthesis-antenna proteins pathway and energy metabolites were downregulated, whereas the transmembrane transport and receptor activities of phosphate and calcium signal pathways were upregulated to maintain growth, achieving balance in the 1 mg/L group. The significantly upregulated steroid biosynthesis promoted the hydrophobicity of plasma membranes and reduced the permeability for water-soluble ions, exacerbating phosphorus deficiency. The downregulation of the Calvin cycle shifted the total carbon metabolism and carbon migration, reducing photosynthesis and respiration but accumulating starch to counteract cell shading and phosphorus deficiency. These findings provide novel insights into the mechanisms underlying the short-term growth stimulation and long-term potential toxic effects of NPs on marine microalgae, thus altering marine carbon and phosphorus cycles.
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Researchers found that high microplastic-to-microalgae ratios paradoxically boosted short-term growth of the marine microalga Porphyridium cruentum by up to 45%, driven by bound exopolysaccharides that adsorbed and sedimented microplastics, though the same aggregation suppressed photosynthesis proteins and DNA repair pathways—revealing a trade-off between acute stress tolerance and long-term cell integrity.
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Researchers studied whether the harmful effects of polystyrene nanoplastics on marine algae are temporary or long-lasting. They found that while some damage, like oxidative stress, was reversible after exposure ended, other effects such as increased cell membrane damage persisted. The study suggests that even at low, environmentally realistic concentrations, nanoplastics can cause lasting disruption to algal metabolism and cell function.
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Researchers exposed a marine microalga important to ocean ecosystems to nanoplastics and found significant disruptions to its lipid metabolism, reducing both biomass and lipid production. The nanoplastics altered the types of fats the algae produced, potentially affecting the nutritional value of these organisms for the marine food web. The findings suggest that nanoplastic pollution could have cascading ecological consequences by disrupting carbon cycling at the base of the food chain.
Effects of nanoplastics on microalgae and their trophic transfer along the food chain: recent advances and perspectives
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This review summarized evidence on how nanoplastics affect microalgae — including growth inhibition, oxidative stress, and altered photosynthesis — and examined trophic transfer of nanoplastics up the food chain, finding that toxicity depended on NP concentration, size, and surface charge.
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Researchers exposed a submerged aquatic plant commonly used in constructed wetlands to polystyrene nanoplastics and measured the impacts on growth, photosynthesis, and metabolism. They found that nanoplastics were absorbed and transported throughout the plant, reducing growth by up to 73 percent and disrupting key metabolic pathways including the citric acid cycle. The study suggests that nanoplastic accumulation in wetland plants could compromise their ability to purify water.
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