新兴优控内分泌干扰物在河口异构型食物网中的介导通路与传递特征

It is a challenge to reveal the transmission effects of pollutants in the food webs with different food sources and heterogeneous trophic structures. The diverse species composition in the estuary, which connects the inland river and the ocean, determines the complex predator-prey relationships and trophic structures. However, the research on the key trophic mediate pathway in the estuarine food webs has not been carried out yet. The emerging priority endocrine disrupting compounds (EDCs) are characterized by their wide sources, long toxic incubation period, and significant harm even at low concentration, which poses a great threat to human survival and species reproduction. In this project, five emerging priority EDCs will be selected as target compounds. In the Pearl River Estuary, stomach and gut contents of aquatic organisms will be analyzed to quantify the diet composition and to construct three food webs with heterogeneous structures along the gradient of inland river, estuary, and offshore. On the basis of stable isotope technique, we will trace the transmission pathways of EDCs along the food chains with different food sources, explore the key functional groups that play as important mediate during the transmission process of EDC, and reveal the bioaccumulation and biomagnification effects of EDCs. Ecopath with Ecosim (EwE), a nutrient transmission model, will be used to construct the energy flow systems of the food webs; Ecotracer, a pollutant transmission model, will be further used to simulate the directional transmission pathway and flux of EDCs in the food webs with heterogeneous structures from temporal and spatial scales. The research achievement of this project will provide theoretical evidence and new ideas for revealing the migration and transformation of high-risk emerging organic pollutants in the ecosystem.

揭示污染物在不同食物来源/营养构型（异源/异构）的食物网中的传递效应是个热点问题。河口连接内河与海洋，多样的物种组成决定了复杂的捕食关系和营养结构，然而，针对污染物在河口食物网传递过程中的介导通路研究还有待深入。内分泌干扰物（EDCs）来源广、潜伏期长、毒性作用量低，对人类生存与物种繁衍构成巨大威胁。本项目以5种新兴优控EDCs为目标物，在珠江河口区，采用胃/肠内含物分析量化各消费者食源组成，组建内河->河口->近海三种食物网架构；基于稳定同位素示踪技术，追溯EDCs在以不同食源为介导的食物链中传递路径，查明传递过程所介导的关键功能类群，揭示EDCs在异源性食物链中的富集/传递效应。采用EwE营养传输模型构建河口食物网能流体系，结合Ecotracer污染物传递模型，从时空尺度模拟EDCs在异构型食物网中的定向传输通路/通量变化。研究成果为揭示高风险新兴污染物在生态系统中迁移转化提供新思路。

本项目聚焦于珠江河口区域，采用常规监测与模型技术相结合的方法，阐明环境中内分泌干扰物（Endocrine disrupting chemicals, EDCs）在河口食物链/网中的富集和传递特征，揭示其迁移转化途径。通过3年的研究，总结科学发现如下：.（1）EDCs主要通过悬浮颗粒物吸附后累积于沉积物中，且呈现显著的时空差异，体现为丰水期高于枯水期，上游石井河污染最为严重，广州市区浓度较高，东莞工业区污染加重，入海口污染程度降低。.（2）壬基酚（4-NP）在肉食性鱼中富集（BAF）最高，而三氯卡班（TCC）在浮游动物食性鱼中富集最高，且BAF值呈现显著的空间差异，即淡水区到咸水区逐渐增加。4-NP在“沉积物->环棱螺”、“颗粒物->沼虾->淡水肉食性鱼”、“颗粒物->浮游动物->七丝鲚->棘头梅童鱼”三条食物链中存在放大效应（BMF>1），说明营养传输通路对污染物的传递和迁移有重要影响。.（3）构建食物网物质循环与能量流动模型Ecopath，发现工业区营养级（TL）最低（≤ 3.0，仅1种肉食性鱼类），污染物传递受限，上游农业区和中游城市区食物网结构复杂（TL≈3.4），下游河口区结构最为复杂（TL≈4.0），污染物传递在中下游河段的传递路径增加，系统稳定性和成熟度提高。.（4）生物累积模型MBAW评测结果与实测值差异在合理范围，说明结果可信；MBAW评测4-NP在食物网中最具富集和放大潜力，其次是辛基酚（4-t-OP）和TCC，3种化合物在珠江河口各区域内的营养级放大因子（TMF）均大于1，表明存在放大效应，且随污染物在环境介质中浓度的增加呈现增强的放大效应。.（5）可视化网络模型（NT）显示，污染物在珠江生态系统中的流通以“颗粒物->碎屑食性鱼类”为主，污染物在该食物链中的流通量达到整个系统的35%，其次是“颗粒物->滤食性鱼类”，流通量占系统总量的20%，而“颗粒物->浮游动物->七丝鲚->棘头梅童鱼”是珠江目前仅存的一条“高通量”食物链。