Ghosh Mira, Rochman Chelsea, Hermabessiere Ludovic, Covernton Garth A
University of Toronto Department of Ecology and Evolutionary Biology, Toronto, Ontario, Canada.
Environ Toxicol Chem. 2025 Jul 30. doi: 10.1093/etojnl/vgaf196.
Microplastics are ubiquitous in the environment and can have toxic effects on organisms. The effects of microplastics can include food dilution. This occurs when an animal feels full after consuming particles but does not gain nutrition from them. This satiety signal might limit further feeding, resulting in malnutrition. Environmental concentrations of microplastics and food are relevant to the risk of food dilution. The ratio of ingested microplastics to food by volume should determine the degree of food dilution and other toxicity pathways. To examine the possibility of a relationship between food availability and the effects of microplastics on animal health, we used a fully factorial design experiment exposing Daphnia magna to three concentrations of microplastic fragments (none, low, high). We exposed Daphnia to a mixture of three microplastic polymers (polyethylene, polyethylene terephthalate, polystyrene) and three levels of food availability (low, medium, high). We found that microplastics negatively affected survival only in the high exposure treatment and that food availability improved survival across all treatments. Higher survival of Daphnia in the high microplastics, high food treatment compared with the high microplastics, medium and low food treatments suggests that the two factors interact additively. Food availability also positively influenced reproduction and growth, whereas microplastic exposure did not. Future studies and the interpretation of past work should closely consider the relationship between food availability and microplastics, as the effect of microplastics on survival appears to be mediated by the abundance of food. Exposures to the same microplastic concentration across different levels of food will produce different experimental outcomes, which will affect the thresholds determined by risk assessments.
微塑料在环境中无处不在，并且会对生物体产生毒性作用。微塑料的影响可能包括食物稀释。当动物摄入颗粒后感到饱腹但并未从中获取营养时，就会发生这种情况。这种饱腹感信号可能会限制进一步进食，从而导致营养不良。环境中微塑料和食物的浓度与食物稀释风险相关。摄入的微塑料与食物的体积比应能决定食物稀释的程度以及其他毒性途径。为了研究食物可利用性与微塑料对动物健康影响之间的关系，我们采用了完全析因设计实验，将大型溞暴露于三种浓度的微塑料碎片（无、低、高）中。我们让大型溞接触三种微塑料聚合物（聚乙烯、聚对苯二甲酸乙二酯、聚苯乙烯）的混合物以及三种食物可利用水平（低、中、高）。我们发现，微塑料仅在高暴露处理中对存活率产生负面影响，而食物可利用性在所有处理中都提高了存活率。与高微塑料、中食物和低微塑料处理相比，在高微塑料、高食物处理中大型溞的存活率更高，这表明这两个因素具有相加性相互作用。食物可利用性对繁殖和生长也有积极影响，而微塑料暴露则没有。未来的研究以及对过去工作的解读应密切考虑食物可利用性与微塑料之间的关系，因为微塑料对存活率的影响似乎是由食物的丰度介导的。在不同食物水平下暴露于相同微塑料浓度会产生不同的实验结果，这将影响风险评估所确定的阈值。
