东寨港人工和天然红树林群落“塑料际”特征差异比较

Comparison of“Plastisphere”Characteristics Between Artificial and Natural Mangrove Communities in Dongzhaigang

作为陆海交界处独特的潮间带生态系统,红树林是阻止微塑料(microplastics,MPs)进入海洋的最后一道屏障。因此沿海红树林已经成为MPs的主要汇集地。为探究人工与自然红树林群落中MPs赋存特征及细菌群落结构的差异,本研究以海南省东寨港红树林自然保护区为研究区域,选择典型人工和天然红树林群落为研究对象,以聚氯乙烯(polyvinyl chloride,PVC)和聚乳酸(polylactic acid,PLA)为目标MPs开展原位暴露实验,比较PVC与PLA两种MPs在人工和天然红树林群落暴露后微观形貌与理化性质的动态变化,并分析不同红树林群落“塑料际”细菌群落差异。结果表明:随着暴露时间的增加,与人工红树林群落中的MPs相比,暴露于天然红树林群落中MPs表面形貌塌陷程度更显著,接触角、结晶度和疏水性变化也更剧烈,表明天然红树林环境暴露加速了MPs的老化过程。人工和天然红树林群落“塑料际”和周围沉积物中细菌群落多样性均差异显著(P<0.05)。暴露于天然红树林群落中的MPs优势菌为厚壁菌门(Firmicutes),而在人工红树林群落中,变形菌门(Proteobacteria)细菌在MPs表面大量定殖。其中天然红树林群落沉积物的pH水平为“塑料际”微生物结构的主控因子(P<0.01),而人工红树林群落沉积物中的NH_(4)^(+)-N含量与“塑料际”微生物多样性呈极显著正相关(P<0.01)。综上所述,相比于人工红树林群落,天然红树林环境可促进MPs的老化效应及“塑料际”表面微生物群落演替。研究结果阐明了天然和人工红树林原位暴露下PLA和PVC的理化性质及“塑料际”的构建过程,为进一步分析MPs“塑料际”与环境的相互作用提供理论依据。

As a distinctive intertidal ecosystem at the interface between terrestrial and marine realms,mangrove repre-sents a pivotal buffer against the influx of microplastics(MPs)into the marine environment,which serves as a principal repository for MPs.To elucidate the inner differences in the temporal alterations in micro-morphology,physicochemical traits and bacterial communities of polyvinyl chloride(PVC)and polylactic acid(PLA),exposure experiments were conducted at the representative artificial and natural mangrove communities in Dongzhaigang Mangrove Nature Reserve in Hainan Province.Results revealed that MPs cultured in the natural mangrove performed more pronounced collapses and substantial fluctuations in contact angle,crystallinity,and hydrophobicity in comparison to that in artificial man-grove environment.This suggests that the natural mangrove environment exposure might accelerate the MPs aging processes.Significant differences were observed between the diversity of MPs bacterial communities and sediments in artificial and natural mangrove(P<0.05).Firmicutes plays a dominate role in MPs exposed to natural mangrove com-munities,while Proteobacteria was the dominant phylum colonized on MPs in artificial mangrove environment.The pH level of natural mangrove sediments was the primary factor for bacterial colonization on“plastisphere”(P<0.01),whereas ammonium nitrogen(NH_(4)^(+)-N)of artificial mangrove habitats showed a highly significant positive correlation(P<0.01)with the microbial community of MPs.In summary,MPs in natural mangrove communities showed more pro-nounced alterations in the surface micromorphology and microbial community succession than that in artificial man-grove communities.The surfaces of the“plastisphere”in natural mangrove communities have a high level of bacterial community richness,and their ability to enrich microorganisms differs from that of the“plastisphere”in artificial man-grove environment.Results of the study provide a foundation for the dynamic changes in physicochemical properties and microbial communities of MPs,which is expected to contribute to further investigations in the potential risks of MPs.