Microplastic pollution in aquatic environments is a growing global concern. Microplastics, defined as plastic fragments smaller than five millimetres, accumulate in freshwater reservoirs, especially in urban areas, impacting resident biota. This study examined the effects of microplastics on the performance and microbiome of Daphnia, a keystone organism in freshwater ecosystems, through both in situ sampling of freshwater ponds and a controlled 23-day in vitro exposure experiment. Using bacterial 16S ribosomal RNA gene amplicon sequencing and whole-genome shotgun sequencing, we analyzed the microbiome's composition and functional capacity in relation to microplastic pollution levels. Urban ponds contained higher microplastic concentrations in water and sediment than natural ponds, with distinct differences in plastic composition. Bacterioplankton communities defined as bacterial assemblages in the water column, were more diverse and richer than Daphnia-associated microbiomes. Overall, the in situ study showed that the composition of the Daphnia-associated community was influenced by many factors including microplastic levels but also temperature and redox potential. Functional analysis showed increased relative abundances of polyethylene terephthalate degradation enzymes and antibiotic resistance genes in microbiomes from high-microplastic ponds. In the in vitro experiment, the bacterioplankton inoculum source significantly influenced Daphnia survival and microbiome composition. Network analysis identified specific taxa associated with microplastics within the Daphnia microbiome. Our findings highlight that urbanisation leads to higher microplastic and antibiotic resistance gene burdens, influencing host-associated microbiomes through taxonomic shifts, functional enrichment, and survival outcomes, with potential implications for the resilience of aquatic ecosystems.

中文翻译：

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微塑料对水蚤相关微生物组原位和体外的影响


水生环境中的微塑料污染是一个日益受到全球关注的问题。微塑料，定义为小于 5 毫米的塑料碎片，在淡水库中积累，尤其是在城市地区，影响居民生物群。本研究通过淡水池塘的原位采样和为期 23 天的受控体外暴露实验，检查了微塑料对淡水生态系统中的关键生物水蚤的性能和微生物组的影响。使用细菌 16S 核糖体 RNA 基因扩增子测序和全基因组鸟枪法测序，我们分析了微生物组的组成和功能能力与微塑料污染水平的关系。城市池塘在水和沉积物中的微塑料浓度高于天然池塘，塑料成分存在明显差异。浮游细菌群落定义为水柱中的细菌组合，比水蚤相关微生物组更多样化、更丰富。总体而言，原位研究表明，水蚤相关群落的组成受许多因素的影响，包括微塑料水平，以及温度和氧化还原电位。功能分析显示，来自高微塑料池塘的微生物组中聚对苯二甲酸乙二醇酯降解酶和抗生素抗性基因的相对丰度增加。在体外实验中，浮游细菌接种物来源显着影响了水蚤的存活和微生物组组成。网络分析确定了与水蚤微生物组中的微塑料相关的特定分类群。 我们的研究结果强调，城市化导致更高的微塑料和抗生素耐药性基因负担，通过分类学转变、功能富集和生存结果影响宿主相关微生物组，对水生生态系统的复原力具有潜在影响。