School of Environment, Nanjing Normal University, Nanjing, China; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
School of Environment, Nanjing Normal University, Nanjing, China.
Sci Total Environ. 2024 Dec 1;954:176841. doi: 10.1016/j.scitotenv.2024.176841. Epub 2024 Oct 10.
A large number of microplastics have been discharged into freshwater ecosystems, where they age and are deposited in the sediment, posing a risk to primary producers, such as submerged macrophytes. Many macrophytes benefit from clonal integration, which lets the population work as a 'macro' organism. Nonetheless, little is known about the differences in phytotoxicity between aged and pristine microplastics, particularly for clonal populations of macrophytes. In this study, we showed that UV-aging changes the characteristics of polyvinyl chloride microplastics (PVC-MPs). Aged PVC-MPs possessed higher hydrophilicity, less chlorine and crystallinity, and more severe toxicity. The pristine PVC-MPs did not affect Vallisneria natans, while the aged PVC-MPs significantly affected the development and structure of the clonal population. The severely aged PVC-MPs reduced the relative growth rate of V. natans by 26 % at the population level. Furthermore, the mother plant (ortet) and offspring (ramet) responded differently to the aged PVC-MPs. A trade-off was observed between the growth rate and stress resistance in the ortets. The ortets increased investment in the root part to tolerate stress when facing exposure to microplastics. In contrast, the ramets were less resistant, as shown by shorter roots, and lower leaf chlorophyll, carbon, and nitrogen concentrations. Notably, the growth of the ramets was maintained and the investments in stolon structure by the ortets were not lessened. The ortet sacrificed itself for the continuation of the ramet. This clonal integration may safeguard V. natans survival and compensate for vegetative expansion. This study sheds new light on how macrophytes respond to microplastics at the clonal population level and provides direct evidence that existing studies may have underestimated the toxic effect of microplastics in freshwater ecosystems.
大量的微塑料已排放到淡水生态系统中，在那里它们会老化并沉积在沉积物中，对初级生产者（如沉水植物）构成威胁。许多沉水植物受益于克隆整合，这使得种群能够作为一个“宏观”生物发挥作用。然而，人们对老化和原始微塑料之间的植物毒性差异知之甚少，特别是对于沉水植物的克隆种群。在这项研究中，我们表明，紫外线老化会改变聚氯乙烯微塑料（PVC-MPs）的特性。老化的 PVC-MPs 具有更高的亲水性、更少的氯和结晶度，以及更严重的毒性。原始的 PVC-MPs 不会影响苦草，而老化的 PVC-MPs 则显著影响了克隆种群的发育和结构。严重老化的 PVC-MPs 使苦草的相对生长率在种群水平上降低了 26%。此外，母株（原株）和子代（分株）对老化的 PVC-MPs 的反应不同。在原株中观察到生长率和抗逆性之间的权衡。当面临暴露于微塑料时，原株会增加对根部分的投资以耐受压力。相比之下，分株的抵抗力较低，表现为根较短，叶片叶绿素、碳和氮浓度较低。值得注意的是，分株的生长得到了维持，原株对匍匐茎结构的投资并没有减少。原株为分株的延续牺牲了自己。这种克隆整合可能保护了苦草的生存，并补偿了其营养繁殖的扩张。本研究揭示了沉水植物在克隆种群水平上对微塑料的响应方式，并提供了直接证据表明，现有研究可能低估了微塑料在淡水生态系统中的毒性效应。
