海河水体富营养化对原生生物群落空间分布格局的影响

Excessive nutrient loading is a major threat to aquatic ecosystems that leads to ecosystems degradation worldwide. Besides managements of the majority of anthropogenically mediated pollutants, controlling nutrient levels with more diverse communities in watersheds is a primary objective of most environmental policy. Protists, as flagship groups of unicellular microorganisms, consist of different eukaryotic lineages which inhabiting all biotopes and playing crucial roles in regulating microbial food webs and nutrient cycling in different ecosystems. Protists in aquatic ecosystems play fundamental ecological roles as primary producers, consumers, decomposers in food webs and structure a primary aquatic ecosystem. Therefore, special attention should be paid to the dynamic relationships of protist community assemblages in different nutrient gradients, and exploring the influence of nutrient factors in structuring protist community patterns, and effects of keystone protist communities for managing nutrient (e.g. nitrogen and phosphorus) uptake and storage, to achieve restoration of damaged rivers by controlling keystone protist communities. Here, we take north three river systems of the Haihe River as research area to address the relationship of nutrient gradients and protist community patterns by examining the phylogenetic structure of community assemblages based on morphological and DNA barcodes databases. We aim to highlight the potential for the Haihe River ecologcial restoration to benefit from assembling keystone protist communities and to suggest several avenues by providing references in regulating nutrient elements and controlling protist communities for pollution ecology research.

营养负载导致的河流生态系统退化问题日益突出，在降低和控制人为影响的同时，亟需开展基本生态功能修复研究工作。原生生物作为一类最具代表性的单细胞真核微生物，类群丰富、分布广泛，在各种生态系统的微食物网和经典食物链中起着重要的枢纽作用，涵盖食物链中生产者、分解者、消费者重要类群，是水生态系统基本生态功能得以维系和正常运转的基石。解析其生物群落结构演化、组建趋势与氮磷等营养元素消耗储备的关系是河流生态功能修复研究亟需解决的关键科学问题。本工作拟以海河流域北三河区段为研究区域，通过不同营养元素梯度下原生生物群落形态数据库、DNA条形码数据库、群落系统发生树构建，重点研究并解析不同营养元素梯度下原生生物群落系统发生关系的演替规律，揭示不同环境因子对应的关键演替群落，为后期通过恢复和稳定特定群落进行海河污染水体生态功能修复奠定基础，也为通过调整营养因子与控制生物群落结构进行河流生态功能修复提供新的思路。

本项目3年来以污染河流为研究区域及单细胞真核微生物为研究对象，对污染胁迫等真核微生物群落多样性及其群落演替规律及演替趋势开展了系统的研究。主要成果包括：1）筛选评估真核微生物多样性研究的barcode基因，且选出适用于直接从环境样本获取真核微生物属或种水平生物多样性的metabarcoding标记基因；2）在时间和空间尺度上完成了研究区域40个样点的环境变量及基于高通量测序分子数据的生物变量的数据库的构建；3) 基于环境变量及生物变量之间的多元统计分析，筛选出铵态氮是造成后生微型生物群落格局发生变化的主导富营养化影响因子，后生微型生物群落是影响真核微生物群落分布格局变化的主要生物因子；4）基于环境变量及生物变量之间的多元统计分析，筛选出铵态氮，硝态氮及总磷是影响关键真核微生物群落系统发育多样性的污染驱动因子；5） 污染胁迫驱动了真核微生物基于遗传距离的多样性分化，不同真核微生物对不同污染梯度产生了适应性进化。以上成果在国际主流刊物发表文章4篇，核心成果形成的2篇文稿数据正在整理成文，相关成果申请人在参加国际、国内学术会议中做过相关口头或者墙报报告展示。

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