淡水浮游动物摄食微塑料过程及影响研究

Ingestion and Effects of Microplastics on Freshwater Zooplankton

近年来,微塑料的环境污染问题受到了国内外广泛关注。前期,大量工作致力于海洋环境中微塑料污染特征及环境效应的研究,而对淡水环境中微塑料的关注相对较少。该文研究了淡水湖泊中浮游动物对微塑料的摄入和排泄过程,并通过21 d繁殖实验研究了微塑料暴露对大型溞(Daphnia magna)的影响。结果表明,来自淡水湖泊中的轮虫、枝角类和桡足类浮游动物能够摄取粒径为0.1、1.0和9.9μm的聚苯乙烯(PS)微球,但无法摄入101μm的PS微球。摄入的PS微球均能在24 h内随粪便排出。大型溞对粒径为0.1和1.0μm的PS微球的摄食率高于9.9μm的PS微球。在1 000 particles/L的暴露条件下,PS微球对大型溞的摄食、生长和存活没有显著影响。但在0.1和9.9μm暴露组中,大型溞的内禀增长率显著降低。长期微塑料暴露可能会对淡水浮游动物的繁殖造成不利影响。

Pollution of microplastics has drawn increasing public concerns in recent years, and a lot of research efforts were devoted to the investigation of fate and effects of microplastics in marine environment, however less information has been available for microplastics in freshwater environs. In this paper, processes of ingestion and excretion of microplastics by zooplankton of a freshwater lake were studied and the effects of microplastic exposure on Daphnia magna, as a model organism, were evaluated in a 21-day reproduction test. The study showed that zooplankton species, such as Rotifera, Cladocera and Copepoda, were able to uptake PS(polystyrene) microspheres of 0.1, 1.0, and 9.9 μm in size, and the microspheres were egested through their digestive tracts within 24 hours together with other gut contents as feces. It was also found that grazing rates of Daphnia magna for 0.1 μm and 1.0 μm PS microplastics were higher for 9.9 μm one; and influences on Daphnia magna ’s algae feeding, growth and survival were barely found when exposed to PS microplastics of concentration of1 000 particles/L; nevertheless, when exposed to microplastics of 0.1 and 9.9 μm the initial reproduction rate of Daphnia magna remarkably decreased suggesting the potential adverse effects of long-term exposure to microplastics on Daphnia magna population.