Microplastics effects on copepods microbiota

Accumulation of plastics debris in the world, especially in marine environment have been well documented during the past decades. Recent studies have found that inorganic surfaces of microplastics (MPs) can be used by microorganisms as living substrates and form an ecosystem named "plastisphere". Some microorganisms present on MPs are capable to produce polymers-degrading enzymes. In addition, MPs can also serve as vectors and carry microorganisms (including potential pathogens) into higher trophic levels through their ingestion by animals. In this study, impacts on copepod's microbiota during chronic exposure of MPs were investigated by exposing copepods to a classic single-use polymer (low density polyethylene - LDPE) and a biodegradable polymer (polybutylene adipate terephthalate - PBAT). Copepods were exposed to "virgin" and "weathered" MPs during four generations at an environmentally relevant concentration, followed by one "detoxification" generation without MPs exposition. Impacts of MPs-exposure on copepods microbiota were investigated using 16 rRNA gene high-throughput sequencing. The result of NMDS analysis showed that copepods (with or without MPs exposure) carried distinguishable microbiota as compared with microbiota of water and microalgae used for maintaining copepods. According to results of PERMANOVA analysis, microbiota of MPs-exposed (both PBAT and LDPE) copepods were significantly different from microbiota of un-exposed copepods during generations 1 to 4. After "detoxification" however, no significant difference in microbiota composition was observed among all generation 5 copepods.

近数十年来，全球塑料碎屑的累积现象，尤其是海洋环境中的此类情况，已得到充分的文献记载。近期研究发现，微塑料（microplastics, MPs）的无机表面可被微生物用作栖息基质，并由此形成名为“塑料圈（plastisphere）”的生态系统。部分附着于微塑料表面的微生物可分泌聚合物降解酶。此外，微塑料还可作为载体，通过被动物摄食的途径，将包括潜在致病菌在内的微生物携带至更高营养级。本研究通过将桡足类暴露于两种聚合物——经典一次性用品所用的低密度聚乙烯（low density polyethylene, LDPE）与可降解聚合物聚己二酸/对苯二甲酸丁二酯（polybutylene adipate terephthalate, PBAT）——探究了微塑料长期暴露对桡足类微生物群的影响。研究中，桡足类在环境相关浓度下，先后暴露于“原生”与“风化”微塑料，持续四代，随后设置一代无微塑料暴露的“脱毒”世代。本研究采用16 rRNA基因高通量测序技术，分析了微塑料暴露对桡足类微生物群的影响。非度量多维标度分析（non-metric multidimensional scaling, NMDS）结果显示，无论是否经微塑料暴露，桡足类所携带的微生物群与养殖用水及投喂的微藻微生物群均存在显著差异。置换多元方差分析（permutational multivariate analysis of variance, PERMANOVA）结果表明，在第1至第4代中，经微塑料（包括PBAT与LDPE）暴露的桡足类，其微生物群组成与未暴露组存在显著差异。但经过“脱毒”世代后，所有第5代桡足类的微生物群组成均未出现显著差异。