天鹅洲故道水生态研究进展

20世纪90年代初, 湖北长江天鹅洲故道水质良好, 鱼类资源丰富, 被认为是建立长江豚类半自然保护区和四大家鱼种质资源生态库的理想场所, 而对之开展了水生态研究, 之后由于成功实现了长江江豚的迁地保护而受到越来越多的关注。学者们从水质和沉积物等环境因素, 浮游植物、浮游动物、底栖动物和高等水生植物等生物因素, 水体初级生产力、渔产潜力和鱼类等资源因素多角度开展了天鹅洲故道水生态研究。天鹅洲故道水质呈恶化趋势。浮游植物数量增加了2个数量级, 且从单细胞个体转变为多细胞群体, 同时带有胶被的蓝藻在种类和密度上占有绝对优势; 浮游动物优势种呈小型化趋势; 底栖动物密度有所下降; 高等水生植物呈逐渐衰退趋势。鱼类资源量呈下降趋势。根据水质化学和生物学评价结果, 结合天鹅洲故道受人类活动的影响, 本文指出故道与长江阻隔、渔业活动和环境污染是天鹅洲故道水生态面临的主要问题, 其通过水质、饵料和栖息地等方面影响长江江豚的可持续性生存。同时, 提出5个方面的建议: 首先, 实施通江工程, 恢复故道水文特征, 提高故道理化环境异质性; 其次, 控制外源和内源营养负荷, 提高故道水体水质; 然后, 持续监测水质、沉积物和水生生物状况, 建立故道水生态数据库; 再次, 实施生态修复工程, 提高水生生物多样性; 最后, 规范渔业活动, 优化故道渔业资源, 为保护天鹅洲故道水环境质量和水生态健康, 维持江豚可持续生存提供依据。

PROGRESS IN STUDIES ON WATER ECOLOGY IN TIAN'E ZHOU OXBOW

In the early 1990s, the Tian'e Zhou Oxbow in Yangtze River in Hubei Province had good water quality and rich fish resources, which was considered to be an ideal location for the establishment of semi-natural reserve for Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) and germplasm ecological reservoir for four major Chinese carps. Consequently, water ecology researches on Tian'e Zhou Oxbow from the environmental factor of water quality and sediments, the biological factor of phytoplankton, zooplankton, zoobenthos and aquatic macrophytes, as well as the resource factor of primary productivity, fish potential production and fish resource have made great pro-gress with the successful implementation of the ex-situ conservation for Yangtze finless porpoise. The water quality in Tian'e Zhou Oxbow showed a trend of deterioration. The number of phytoplankton increased by two orders of mag-nitude, and the form of phytoplankton changed from single-celled individuals to multicellular colony, and cyanobac-teria with gelatinous envelope displayed an absolute predominance in species and densities. The dominant species of zooplankton showed a trend of miniaturization. The density of zoobenthos decreased dramatically. Aquatic macro-phytes displayed a trend of gradual recession. Fish resources showed a downward trend. The chemical evaluation and biological assessment of water quality and human activities on Tian'e Zhou Oxbow indicated that disconnection between Oxbow lake and Yangtze River, fishery activity and environmental pollution were the main factors impacting water ecology of Tian'e Zhou Oxbow, which affected the sustainability of Yangtze finless porpoise through water qua-lity, bait resources and habitat. Five suggestions were proposed to protect water environment quality and water ecologi-cal health, and then maintain the sustainable survival of Yangtze finless porpoise. First, the connecting engineering between Tian'e Zhou Oxbow and Yangtze River should be implemented to restore the water ecological characteristics and improve the heterogeneity of physicochemical environment. Second, nutrient loading from internal and external source should be controlled to improve the water quality of Tian'e Zhou Oxbow. Third, the condition of water quality, sediments and aquatic organisms should be monitored continuously to establish the database of water ecology. Fourth,ecological restoration project should be implemented to improve the biodiversity of aquatic organism in Tian'e Zhou Oxbow. Finally, fishery activity should be regulated to optimize fishery resources.