底栖动物改良疏浚区底质促进沉水植物恢复的效应及机理研究

It is significant to reconstruct submerged plants in a dredged area. But the sediments in dredged area are not entirely suitable for the growth of submerged plants. Benthic invertebrate can improve the physical, chemical and biological environment. It has potential to promote the restore of submerged plants in dredged area. However, it is still not clear about the effects and mechanisms of benthic invertebrate’s improving sediments and submerged plants growth in dredged area. Therefore, relying on the Dongqian Lake dredging project, a series of experiments would be conducted to study the effects of benthic invertebrate on the reconstruction of submerged plants in dredged area. Corbicula fluminea, Tubifex, Vallisneria spiralis, Potamogeton crispus would be used as the main subjects. The study content include: finding the limiting factors of submerged plants growth in dredged area, getting the key point for the sediments improving and the reconstruction of submerged plants; promoting the sediments in a dredged area, testing the growth status of submerged plants in this area, studying the effectiveness of benthic invertebrate on the recovery of submerged plants in dredged area and mechanisms there of; conducting mesocosm experiments to verify and optimize the ability of benthic invertebrate to promote submerged plants recovery in dredged area. The results of this study would provide theoretical and practical supports to the reconstruction of submerged plants in dredged area. Finally, we are expected to find a new way to integrate sediment dredging and reconstruction of submerged plants.

在湖泊疏浚区域重建沉水植物具有重要意义，但是疏浚区沉积物并不完全适合于沉水植物生长。底栖动物可以改善沉积物物理、化学和生物环境，具有促进疏浚区沉水植物恢复的潜能，但是相关效应和机理并不明确。因此本项目拟依托于东钱湖疏浚工程，以河蚬、颤蚓、苦草、菹草为主要研究对象，对底栖动物促进沉水植物在疏浚区重建的作用进行科学研究。具体内容包括：研究湖泊疏浚区沉水植物恢复的限制因子，为改善疏浚区底质和优化疏浚区沉水植物重建提供切入点；研究底栖动物对疏浚区沉积物的改良，以及在改良后的沉积物中种植沉水植物的生长情况，阐明底栖动物促进疏浚区沉水植物恢复的实施方式、效应及机理；开展围隔实验，验证与优化底栖动物促进疏浚区沉水植物恢复的功能。研究结果可为底栖动物促进疏浚区沉水植物重建提供实践和理论基础，建立一条湖泊疏浚与沉水植物重建相集成的新途径。

在疏浚区域重建沉水植物具有重要意义；底栖动物可以改善沉积物环境，具有促进疏浚区沉水植物恢复的潜能，但是相关效应和机理并不明确。本项目通过室内微宇宙实验和野外跟踪调研，以疏浚后的湖泊和黑臭水体为研究对象，利用16sRNA高通量测序、示踪玻璃珠等技术，研究了1）湖泊疏浚的生态环境效应及其对沉水植被恢复的影响；2）单一底栖动物（颤蚓）和底栖动物联合（颤蚓+河蚬）作用对湖泊疏浚区沉水植被重建的效应和机理；3）颤蚓对黑臭水体疏浚后的先锋修复作用。研究表明，疏浚工程可能只会对湖泊生态系统健康产生短期（1-2年）的积极效应，建议在此期间开展沉水植物引种。低温（<15 ℃）低生物量（<75 g/m2）的颤蚓更有利于增加沉积物微生物总活性、改善其营养盐和氧化还原环境；但是，单一的颤蚓会让上覆水水质变差，无法促进湖泊疏浚区沉水植物恢复。颤蚓与河蚬联合作用与单一物种作用时相比扰动深度更深、上覆水水质更差；河蚬作为本地种单独存在时有利于维持健康水环境，可促进沉水植物的恢复。高通量测序表明，Ignavibacterium属、Deferrisoma属、Sh765B_TzT_35属在苦草&颤蚓组富集明显；拟杆菌Bacteroidetes门、脱硫菌Desulfarculaceae科、norank_f__B1_7BS属在苦草&颤蚓&河蚬组富集明显；添加底栖动物和播种苦草没有引起沉积物微生物多样性的改变，但是可能加强沉积物硝化作用；河蚬会改变蓝藻的群落结构。低生物量（63.7 g/m2）颤蚓可在疏浚后的黑臭水体沉积物中存活，可作为黑臭水体疏浚后的先锋物种进行修复，且不会增加环境风险。本研究提出，在疏浚结束一定时期内（1-2年）选取土著底栖动物修复疏浚区，再选择沉水植物成株移栽的方式将疏浚工程与沉水植物重建相集成的总体思路。本研究为底栖动物促进疏浚区沉水植物重建提供了一定的实践和理论基础。