阳宗海硅藻群落对水体污染和水文调控的长期响应模式

Long-term pattern of diatom community responses to water pollution and hydrological regulation in Yangzong Lake

在人类活动持续干扰的背景下,云南部分湖泊面临着污染物输入增加的环境压力,特别是营养盐富集和重金属污染。以云南地区遭受过严重工业污染的阳宗海为研究对象,通过沉积物硅藻群落、砷浓度、营养元素与稳定同位素、粒度等多指标分析,结合文献记录和湖泊调查结果,揭示了阳宗海硅藻群落对湖泊富营养化和砷污染的长期响应特征,并识别了不同时期的主要环境压力与其驱动强度。结果表明:长期的营养盐累积使得浮游硅藻逐渐占据优势地位,且耐污染的底栖硅藻种的快速增加与砷污染出现的时段一致。在阳宗海长期富营养化的背景下,当水体砷污染物浓度达到一定阈值水平后,硅藻群落结构的改变和多样性的降低都指示了湖泊生态系统发生了灾难性的转变。同时1965年开始的湖泊引水工程导致了贫营养种的突然增加。因此,水体富营养化、重金属污染与湖泊水文调控是导致阳宗海硅藻群落长期变化的主控因子,对阳宗海的生态修复与综合治理需要综合考虑不同胁迫因子的长期影响与驱动作用。

In the context of expanding anthropogenic disturbances, many lakes in Yunnan province have experienced increasing inputs of pollutants such as nutrients and heavy metals.Here, we applied multi- proxy sediment analyses for Yangzong Lake with known history of industrial pollution, aiming to reveal the long- term response of the diatom communities to eutrophication and arsenic pollution and identify the main environmental stressors. The diatom community changes showed that long-term nutrient enrichment has led to the gradual increase in planktonic diatoms, however, their rapid replacement by metal- tolerant diatoms（i.e.Achnanthes minutissima） clearly reflected the impact of industrial wastewater pollution. Under the conditions of long-term eutrophication and hydrological regulation, the diatom community structure and species richness displayed a catastrophic shift when the lake- water arsenic reached a threshold level, suggesting that the Yangzong Lake has experienced a shift of stable state around 2008. In addition, water diversion project implemented since 1965 led to the increase of an oligotrophic endemic species（Cyclotella rhomboideo-elliptica）, which thereafter showed a rapid decrease in abundance and was later decimated as a result of ongoing nutrient enrichment. In all, lake eutrophication, heavy metal pollution and hydrological regulation were among the main factors driving the long- term changes of diatom communities. Therefore our sediment records provided long- term trajectory of lake pollution and biological responses,which can facilitate ecological restoration and catchment management for polluted lakes.