长江中下游四大淡水湖生态系统完整性评价

长江中下游地区是我国淡水湖泊集中分布区域,研究该区域湖泊生态系统完整性对于湖泊生态系统保护和恢复具有重要意义。物理、化学和生物完整性指标已经广泛应用于河湖生态系统健康评价,但是缺少物理、化学和生物完整性的综合评价方法。以历史调查状况为主要参照系统,构建了基于物理、化学和生物完整性的多参数湖泊完整性综合评价指标体系,结合近年来长江中下游四大淡水湖(洞庭湖、鄱阳湖、巢湖、太湖)生态系统调查数据,对四大淡水湖生态系统完整性进行了评价。结果表明,洞庭湖、鄱阳湖、巢湖和太湖的综合得分分别为66、71、57和57。根据评价等级划分标准,洞庭湖和鄱阳湖生态系统完整性状况都达到"好"的等级,而巢湖和太湖则处于"一般"等级;结果显示,该指标能够表征人类活动对于湖泊生态系统完整性不同方面的干扰,且能够反映四大淡水湖生态系统完整性历史变化状况。因此,该方法可以作为长江中下游淡水湖泊生态系统完整性综合评价的工具并能够为湖泊生态系统的保护和恢复提供科学支撑。

Aquatic ecological integrity assessment of four large lakes in the middle-to-lower reaches of the Yangtze River, China

Many freshwater lakes are distributed in the middle-lower reaches of the Yangtze River basin; they are of great importance as water supply resources and for aquatic eco-system maintenance. The evaluation of lake health and its variation is useful for environmental management of lake ecosystems. Numerous indices related to physical, chemical, and biological integrity are widely applied to assess the health of lake ecosystems. However, few studies have assessed the ecological integrity of lakes using a combination of physical, chemical, and biological integrity metrics in China, especially at a regional scale. Based on a review of previous research, a lake ecological integrity index (LEII) including physical, chemical, and biological (algae, macroinvertebrates, and fish) integrity metrics was developed to evaluate four large lakes in the middle-lower reaches of the Yangtze Basin. Reference conditions were defined mainly based on historical data collected in the 1950s and 1960s, when the status of lake ecological integrity was acknowledged as "good." The final score for the lake ecosystems integrity index was calculated by combining the scores for physical, chemical, and biological integrity metrics. Additionally, the scores were divided into five categories, i.e., excellent, good, fair, poor, and very poor. The LEIIs of Lake Dongting, Poyang, Chaohu, and Taihu were 66, 71, 57, and 57, respectively. Based on the LEII scores, Lake Dongting and Lake Poyang were rated "good" and Lake Chaohu and Lake Taihu were "fair." However, the individual indices showed different status for the four large lakes. For instance, the physical integrity index was higher than 80 for all lakes except Chaohu Lake (71), suggesting an "excellent" status. The highest score for the chemical integrity index was observed in Lake Poyang (71) and the lowest score in Lake Taihu (56). Three were rated as "good." The biological integrity index ranged from 46 in Lake Taihu to 65 in Lake Poyang, two were rated as "fair." The four large lakes suffered from various degrees of damage in physical, chemical, and biological integrity, and these differences demonstrated the effects of human activity on the ecological integrity of the four large lakes over the past 50 years. Consequently, the LEII can be used as a tool to assess the ecological integrity of the four large lakes along the Yangtze River, and the results provide a scientific basis for lake ecosystem restoration and protection.