posted on 2024-01-31, 15:39authored byMei Wang, Zhiliang Huang, Chao Wu, Shuai Yan, Hai-Tao Fang, Wei Pan, Qiao-Guo Tan, Ke Pan, Rong Ji, Liuyan Yang, Bingcai Pan, Ping Wang, Ai-Jun Miao
Microplastics
(MPs) are pollutants of global concern, and bioaccumulation
determines their biological effects. Although microorganisms form
a large fraction of our ecosystem’s biomass and are important
in biogeochemical cycling, their accumulation of MPs has never been
confirmed in natural waters because current tools for field biological
samples can detect only MPs > 10 μm. Here, we show that stimulated
Raman scattering microscopy (SRS) can image and quantify the bioaccumulation
of small MPs (<10 μm) in protozoa. Our label-free method,
which differentiates MPs by their SRS spectra, detects individual
and mixtures of different MPs (e.g., polyethylene, polypropylene,
polyvinyl chloride, polyethylene terephthalate, polystyrene, and poly(methyl
methacrylate)) in protozoa. The ability of SRS to quantify cellular
MP accumulation is similar to that of flow cytometry, a fluorescence-based
method commonly used to determine cellular MP accumulation. Moreover,
we discovered that protozoa in water samples from Yangtze River, Xianlin
Wastewater Treatment Plant, Lake Taihu and the Pearl River Estuary
accumulated MPs < 10 μm, but the proportion of MP-containing
cells was low (∼2–5%). Our findings suggest that small
MPs could potentially enter the food chain and transfer to organisms
at higher trophic levels, posing environmental and health risks that
deserve closer scrutiny.