淡水池塘“塑料圈(plastisphere)”微环境特性及其对鲢鳙的生态效应

As an emerging contaminant, the impacts of microplastics on aquatic ecosystem have received worldwide attention. Due to their small particle size and large specific surface area, microplastics can provide an attachment substrate for microorganisms thus forming the plastisphere. Microplastics as a biological vector can potentially alter the structure and function of microbial community, and thus, affact the nutrient cycling and energy flow of water ecosystem. Under the influence of both continental input and human aquaculture activities, the fishery waters are inevitably polluted by plastics. However, studies on the characteristics of plastisphere and its ecological effects in fisheries water environment are scarce to the present. This project will adopt a method combining field investigation and mesocosm experiments. Firstly, the characteristics of microecological environment of plastisphere in freshwater aquaculture ponds were analyzed. On the basis of these results, the silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis), which are easy to ingest microplastics and have important ecological functions, will serve as models to investigate the ecological effects of plastisphere. The effects of plastisphere on the compositional and functional structures of intestinal microbiota of silver and bighead carps will be explored by metagenomics and metabolomics. The food sources and feeding selectivity of silver and bighead carps under the exposure of plastisphere will also be examined by using stable isotope and fatty acid tracing techniques. To ultimately reveal the mechanism underlying trophic plasticity of silver and bighead carps, correlation analysis will be conducted on gut microbiota and feeding information. The results of this project will provide suggestions for the assessment of ecological risks arising from exposure to microplastics and give some implications for green and sustainable development of aquaculture industry.

作为一种新型污染物，微塑料对水域生态系统的影响受到日益重视。微塑料由于粒径小、比表面积大，可为微生物提供附着基底，组合形成微环境“塑料圈(plastisphere)”。微塑料作为生物载体会潜在地改变微生物群落的结构与功能，影响生态系统的物质循环和能量流动。受陆源输入和人类养殖活动的共同影响，渔业水域不可避免的遭受塑料污染，但目前有关渔业环境“塑料圈”及其生态效应的研究相对匮乏。本项目拟采用现场调查和围隔实验法，首先对淡水池塘“塑料圈”微生态环境特征进行分析，在此基础上，以易于摄食微塑料且具重要生态功能的鲢鳙为受试对象，采用宏基因组和代谢组学技术分析“塑料圈”微生态对鲢鳙肠道菌群结构及功能的影响，并运用稳定同位素和脂肪酸示踪技术解析鲢鳙食源利用的变化，最终阐明微塑料条件下鲢鳙食性可塑性及其微生物机制。相关研究结果可为渔业水域微塑料的生态风险评价提供科学依据，对水产养殖业绿色发展具有重要意义。

受陆源输入和人类养殖活动的共同影响，水产养殖环境不可避免的遭受塑料污染。微塑料由于粒径小、比表面积大，可形成塑料圈，潜在改变养殖系统微生物群落结构与功能。本项目对上海地区淡水养殖池塘微塑料赋存特征以及塑料圈群落结构功能进行了调查分析，然后采用宏基因组和稳定同位素技术，解析了塑料圈条件下池塘养殖鲢肠道菌群结构与功能响应，量化了鲢对不同食源的利用效率，阐明了微塑料作用下鲢食性可塑性响应的微生物机制。我们在上海8个养殖区淡水池塘水体和底泥中均检测到了微塑料，水体污染丰度在36.25±6.79 items/L，底泥污染丰度在271.65±164.83 items/kg，主要为透明、黑色和白色微纤维，主要类型为聚乙烯和聚丙烯。塑料圈生物群落较水体群落具更高的多样性，代谢通路显著富集，且与塑料颜色相关。塑料圈可以从周围环境中选择性富集氮功能微生物和基因，促进水体氮转化，且与微塑料赋存生境相关。微塑料导致鲢肠道菌群丰富度和均匀度增加，放线菌、厚壁菌和梭菌丰度降低，糖苷水解酶和糖脂酶功能占比提高，且与鲢δ13C和δ15N值具有较高的正向相关性。塑料圈显著影响鲢肠道代谢谱，导致乙酸、戊酸和己酸含量增加，丙酸和丁酸含量降低，乙酸和丁酸与鲢肠道差异菌属相关性最高。微塑料暴露后，鲢δ13C值与颗粒有机物POM更接近，POM对鲢的食物贡献显著提高，而浮游植物和浮游动物的食物贡献均下降，表明微塑料抑制了鲢对浮游生物的利用。微塑料在鲢肠道内的积累改变了肠道微生物结构与功能，进而导致鲢食源利用的变化。相关研究结果可为养殖池塘微塑料的生态风险管理提供科学依据，对水产养殖健康可持续发展具有重要意义。

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