Department of Hydrobiology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
Department of Hydrobiology, Faculty of Biology, University of Warsaw, Warsaw, Poland; Department of Environmental Microbiology and Biotechnology, Institute of Microbiology, Faculty of Biology, University of Warsaw, Poland.
Environ Pollut. 2022 Nov 15;313:120121. doi: 10.1016/j.envpol.2022.120121. Epub 2022 Sep 8.
Microplastic pollution is currently one of the most intensely studied ecological issues. Numerous studies have estimated the distribution and concentration of microplastics in various environments and determine how they affect their inhabitants. Much less effort has been place on assessing the possible effects of microplastics on interactions between organisms, including interspecific competition. Our aim was to test the hypothesis that the presence of microplastics affects the proportion of individuals of coexisting species and the elimination rate of the inferior competitor. The hypothesis was tested in competitive experiments done in the absence and presence of spherical non-biodegradable polystyrene and polyethylene and biodegradable polyhydroxybutyrate in environmentally relevant densities. In each of the experiments, we used three different pairs of closely related planktonic species of the genus Daphnia composed of the superior and inferior competitor: D. pulex and D. magna, D. magna and D. galeata, D. pulex and D. galeata. The results support our hypothesis and demonstrate each microplastic type had a different effect on the density of the competing species. The presence of polystyrene and polyethylene lowered the density of the superior competitor in each of the three pairs, at least partially due to a reduction in the number of gravid females, but not their fecundity. The presence of the polyhydroxybutyrate, in turn, increased the population density of D. magna in the variants with each of the two remaining species. Moreover, the presence of microplastics affected the elimination rate of the inferior competitor, i.e. polystyrene expedited the exclusion of D. magna by D. pulex, and polyhydroxybutyrate hampered the exclusion of D. magna by D. pulex. Our results suggest that long-term exposure to environmentally relevant densities of both non-biodegradable and biodegradable microplastics may affect the relative abundance of co-occurring species in zooplankton communities, and thus the functioning of aquatic ecosystems.
微塑料污染目前是生态领域研究最热门的议题之一。大量研究已经估算了不同环境中微塑料的分布和浓度，并确定了其对居住其中的生物的影响。然而，人们很少关注微塑料对生物相互作用（包括种间竞争）的潜在影响。我们的目的是检验以下假设：微塑料的存在会影响共存物种个体的比例以及劣势竞争者的淘汰率。该假设在缺乏和存在球形不可生物降解聚苯乙烯和聚乙烯以及环境相关密度的可生物降解聚羟基丁酸酯的竞争实验中进行了测试。在每个实验中，我们使用了由优势和劣势竞争者组成的三个密切相关的浮游生物属 Daphnia 种对：D. pulex 和 D. magna、D. magna 和 D. galeata、D. pulex 和 D. galeata。结果支持我们的假设，并表明每种微塑料类型对竞争物种的密度有不同的影响。聚苯乙烯和聚乙烯的存在降低了每个三对中的优势竞争者的密度，至少部分原因是可育雌性个体数量减少，但不影响其繁殖力。相反，聚羟基丁酸酯的存在增加了 D. magna 在其余两种物种存在的变体中的种群密度。此外，微塑料的存在影响了劣势竞争者的淘汰率，即聚苯乙烯加速了 D. pulex 对 D. magna 的排斥，而聚羟基丁酸酯阻碍了 D. pulex 对 D. magna 的排斥。我们的研究结果表明，长期暴露于环境相关密度的不可生物降解和可生物降解微塑料可能会影响浮游动物群落中共存物种的相对丰度，从而影响水生生态系统的功能。
