典型小节肢类土壤动物食物链在重金属污染过程中的演变与生态系统指标体系的建立

Soil micro-arthropods have being considered as important biological receptor for establishment of bio-indicator system due to their important role and special status in soil ecosystem. Present situation of soil heavy metal pollution needs more objective and precise bio-indicator system, which demands to promote the present indicators up to the level with ecosystem feature of biological interaction and its structure and function. The present project will apply a representative soil micro-arthropod food chain "soil predatory mites - soil born Collembola - soil decomposition fungi" as model indication organism system and study: (1) effects of heavy metal pollution on structure and function of the food chain, by analysis of the biological characteristics in different trophic levels, processes of soil ecosystems and C and N nutrient absorption by plants; (2) biological processes and ecological toxicity effect of heavy metals' transferring in the food chain, and the transferring mechanisms related to nutrients, by analysis of origin of metals entering to food chain, bioaccumulation or metabolism and fate of the metals in the food chain, and the relationship between transferring of heavy metals and C and N nutrients through the food chain; and (3) effects of heavy metals on self regulation of food chain, by analysis of trophic cascade of food chain. On the basis of the studies above, evolvement and mechanisms of ecosystem characteristics of the food chain during heavy metal pollution, bio-indicators with the ecosystem characteristics, and the bio-indicator system and the soil food web forecast model will be elucidated, screened and established, respectively. Laboratory and field experimental systems will be designed. 13C and 15N labeled litter and isotope natural abundance of C3 and C4 plant will be applied to track C and N nutrients, biomarkers of fatty acid and intestinal content DNA to analyze the relation among trophic levels, and trace metal analysis methods to determine metals in body of the soil animals and fungi.

土壤小节肢类由于其在物质循环中的重要作用，始终作为重要受体用于指标建立。当今重金属污染需要更客观、准确的指标体系，要求将现行单一属性指标提升到考虑生物间相互作用并体现其结构和功能的生态系统水平上。本项目以土壤典型小节肢类食物链"捕食螨-弹尾目昆虫-真菌"为模式指示生物，通过分析各营养层生物特征、土壤生态系统过程和植物C、N养分吸收，研究重金属对食物链结构和功能的影响；通过在食物链传递中来源、富集或代谢、去向及与C、N传输的关联，研究污染物传递的生物过程、毒性效应和养分机理；通过营养级联效应，研究污染对食物链自身调控机制的影响。从而，阐明食物链在重金属污染中的演变机理、筛选食物链特征指标并建立指标体系和土壤食物网预测模型。实验采用室内和大田系统，养分定位用13C和15N同位素追踪及C3和C4植物自然丰度，食物链营养关系用脂肪酸和肠道内含物DNA生物标志物，动物和真菌体内重金属用生物痕量技术。

以土壤典型食物链“捕食性螨-跳虫-凋落物/真菌”为模式生物，通过Cd对食物链结构与功能影响、在食物链中传递过程和生态毒性及其与N养分关联、以及食物链营养级联效应对污染响应机制等的研究，阐明Cd与食物链相互作用、传递效率、及营养级关系自我调控机制等生态系统特征在重金属污染过程中的演变规律和机理，筛选食物链生态系统特征指标，建立指标体系。.1. 研制了温度梯度动物样品收集设备（回收率达90%以上）和计数与测量设备（0.2-0,8mm幼虫体长测量误差<10%）；建立微样品量组织内Cd测定（样品量15-25 mg降低到50-150μg）和同位素15N测定（自然和标记样品量分别约400μg和50μg）；筛选华东区优势种东洋棘跳和“凋落物/真菌-跳虫-螨”食物链作为模式生物；建立了种群指标（存活率、繁殖率、成虫生长率和幼虫生长率），从而，建立了室内研究平台。.2. 对浙江、江西、广东、云南、甘肃等农田污染区和矿区十余个点土壤动物进行了调查，包括甲螨、前气门、无气门群和中气门目的双毛懒甲螨、凹纹闭甲螨和棘下盾螨等种类，等节跳和棘跳Bonetrura boneti和 Onychuous yodai等种类。结果表明：不同类型田、不同类群反应不同；体内Cd浓度随土壤Cd浓度升高；生活史和性别特征对土壤污染敏感。在此基础上建立了野外研究规范。.3. Cd通过食物链在捕食者体内高效富集，被捕食者将Cd传递给子1代而毒害捕食者的子1代，因而高阶营养级较低阶受毒害更大；同位素15N追踪表明:食物中Cd升高，其取食者获取N下降，但15N自然丰度增加，即Cd影响取食者的N吸收和15N/14N在体内分馏；捕食者对被捕食种群具调控作用，即捕食会改变传统指标的相对敏感性，低Cd浓度时，“跳虫-捕食螨”体系对毒性具缓冲作用，而高Cd浓度时，增大毒性。.4. 筛选出白符跳金属硫蛋白（MT）阳性克隆为995bp，其产物mRNA随食物Cd浓度而诱导上调；找到并拼装完成了东洋棘跳β-actin基因；通过二代测序和RT-PCR扩增比对，获得了3个差异基因，eif-2c、Prisilkin-39和Uncharacterized protein；获得MT-GFP重组蛋白。