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Comparative assessment of MP effects on pigment composition and lipid profiles in three marine microalgae
Summary
Researchers exposed three marine microalgae species to polyethylene and polypropylene microplastics and found that the particles altered pigment composition and lipid profiles in species-specific ways. Microplastic exposure generally reduced photosynthetic pigments and shifted fatty acid profiles, with effects varying depending on the polymer type and concentration ratio. The study suggests that microplastic pollution could disrupt the biochemistry of ecologically and commercially important microalgae at the base of marine food webs.
Microplastics (MPs) are emerging marine contaminants, yet polymer-specific effects on microalgal physiology and lipid metabolism remain insufficiently understood. This study evaluated the responses of three commercially and ecologically relevant marine microalgae-Nannochloropsis sp., Chaetoceros sp., and Isochrysis sp.-grown in f/2 medium under controlled laboratory conditions and exposed to polyethylene (PE) and polypropylene (PP) MPs at 50 and 100 mg/L in 50:50 and 70:30 (PE: PP) ratios. MP morphology and algal-MP interactions were examined using scanning electron microscopy (SEM). Growth, pigment content, and total lipids were quantified, and fatty acid methyl ester (FAME) profiles were analysed by gas chromatography-flame ionization detection (GC-FID). Elevated MP exposure significantly inhibited growth, with stronger effects under PE-dominant treatments. Nannochloropsis sp. showed the greatest growth reduction (29.36%), followed by Isochrysis sp. (23.58%) and Chaetoceros sp. (15.70%). At 100 mg/L, chlorophyll and carotenoid contents declined across all species. Total lipid content decreased under PE-rich MP exposure, accompanied by marked alterations in fatty acid methyl ester (FAME) profiles. Nannochloropsis sp. exhibited increased proportions of unsaturated fatty acids, particularly α-linolenic acid (C18:3n3), indicating metabolic adjustment to MP-induced stress. In contrast, Chaetoceros sp. showed reduced nervonic (C24:1) and oleic (C18:1) acids, suggesting disruption of long-chain fatty acid biosynthesis, while Isochrysis sp. displayed significant reductions in tricosanoic acid (C23:1) relative to the control. Overall, long-chain fatty acids dominated (55-75%), with MP stress promoting species-dependent elongation and desaturation processes. These findings demonstrate that MP polymer composition critically influences microalgal growth, pigment production, and lipid metabolic pathways, with implications for algal biochemical composition and biofuel-relevant traits. Future studies should examine long-term, environmentally relevant microplastic exposures and underlying mechanisms affecting microalgal physiology and lipid metabolism.