夏季砷和富营养化的交互作用对叶绿素a的影响

Effects of Interaction between Arsenic and Eutrophication on Chlorophyll a in Summer

摘要: 在全球多重压力源叠加的背景下，水生生态系统日益受到重金属污染与富营养化等复合胁迫的影响。为探究砷(As)污染与富营养化交互作用对初级生产力的影响及其季节性差异，本研究通过室外控制实验，设置了低、高两种营养水平及16个砷浓度梯度(0~1000 μg/L)，对比分析了水体中总氮(TN)、总磷(TP)及叶绿素a (Chla)的动态变化，并采用广义加性模型(GAM)分析各环境因子对叶绿素a的影响。结果表明，实验中各处理组砷浓度维持稳定，总磷、总氮及叶绿素a浓度均呈现明显分异。其中在单独环境因子的影响中，水体营养水平对叶绿素a的影响最为显著(R² = 0.7429, F = 9.815, p < 0.001)，砷(R² = 0.3937, F = 2.6117)，总磷(R² = 0.3829, F = 1.7558)亦表现出极显著独立影响(p < 0.001)，总氮表现出显著独立影响(R² = 0.1803, F = 1.5434, p = 0.02)，表明水体营养水平是本研究系统中浮游植物生长的关键限制因子，重金属砷与氮，磷输入均为调控藻类生物量的重要驱动因素。在不同营养背景下，叶绿素a对砷的响应模式存在差异，低营养组中叶绿素a随砷浓度升高呈缓慢上升趋势，高营养组则呈先升后降态势，表明砷的生态效应受背景营养水平调节，砷与营养盐的交互作用对叶绿素浓度的影响达到极显著水平(R² = 0.79, F = 36.86, p < 0.001)，且影响程度明显高于个环境因子的独立影响。本研究结果呈现出，砷与营养盐作为独立压力源对叶绿素a浓度的影响并非存在单一机制，强调在多重压力源背景下，需同时关注营养盐输入与有毒污染物对水生生态系统的独立及潜在联合，对在水环境治理与复合污染风险评估政策有一定意义。

Abstract: In the context of multiple global stressors, aquatic ecosystems are increasingly affected by combined pressures such as heavy metal pollution and eutrophication. To investigate the interactive effects of arsenic (As) contamination and eutrophication on primary productivity and their seasonal variations, an outdoor controlled experiment was conducted. Two nutrient levels (low and high) and 16 arsenic concentration gradients (0~1000 μg/L) were established. The dynamic changes of total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chla) in the water were compared and analyzed using a generalized additive model (GAM) to examine the effects of various environmental factors on chlorophyll a. The results showed that arsenic concentrations remained stable across treatment groups throughout the experiment, while TN, TP, and Chla concentrations exhibited clear differentiation. Among individual environmental factors, nutrient level had the most significant impact on chlorophyll a (R² = 0.7429, F = 9.815, p < 0.001). Arsenic (R² = 0.3937, F = 2.6117, p < 0.001) and total phosphorus (R² = 0.3829, F = 1.7558, p < 0.001) also demonstrated highly significant independent effects, while total nitrogen showed a significant independent effect (R² = 0.1803, F = 1.5434, p = 0.02). These results indicate that nutrient level was the key limiting factor for phytoplankton growth in this experimental system, while both arsenic and nutrient (N, P) inputs served as important drivers regulating algal biomass. The response patterns of chlorophyll a to arsenic differed across nutrient backgrounds: in the low-nutrient group, chlorophyll a showed a gradual increasing trend with rising arsenic concentrations, whereas in the high-nutrient group, it exhibited an initial increase followed by a decrease. This suggests that the ecological effect of arsenic is modulated by background nutrient conditions. The interaction between arsenic and nutrients had a highly significant effect on chlorophyll a concentration (R² = 0.79, F = 36.86, p < 0.001), with a magnitude substantially exceeding the independent effects of each environmental factor. These findings indicate that the effects of arsenic and nutrients as individual stressors on chlorophyll a concentration are not governed by a single mechanism. This underscores the need, in the context of multiple stressors, to pay simultaneous attention to the independent and potential combined effects of nutrient inputs and toxic pollutants on aquatic ecosystems. The study provides insights for water environment management and policies related to composite pollution risk assessment.