College of Resources and Environment, Southwest University, 1 Tiansheng Road, Beibei District, Chongqing, 400716, China; National Base of International S&T Collaboration on Water Environmental Monitoring and Simulation in Three Gorges Reservoir Region, Chongqing, 400716, China; College of Environment, Hohai University, No.1 Xikang Road, Gulou District, Nanjing, 210098, China; Organization of African Academic Doctors, Off Kamiti Road, P.O. Box 25305-00100, Nairobi, Kenya.
College of Resources and Environment, Southwest University, 1 Tiansheng Road, Beibei District, Chongqing, 400716, China; National Base of International S&T Collaboration on Water Environmental Monitoring and Simulation in Three Gorges Reservoir Region, Chongqing, 400716, China.
Environ Pollut. 2022 Jun 15;303:119103. doi: 10.1016/j.envpol.2022.119103. Epub 2022 Mar 10.
Nutrient availability, is a crucial anthropogenic stressor promoting freshwater eutrophication and rapid expansion of harmful algal blooms (HABs), deteriorating water quality and threatening public health worldwide. The estimation of the HABs community responses to diel changes in the nutrients while characterizing the ecosystem growth limiting factors, is key to prudent watershed management. The present study investigated the short-term variabilities in autumn cyanobacterial responses to the external nutrient inputs into the Pengxi River using the nutrient addition bioassay approach. Results reveal phytoplankton community structure dominated by the cyanobacteria: Anabaena and Aphanizomenon spp. (relative abundance = 46.20% equilibrium abundance), followed by the diatoms, out of which Lindayia bodaniica, are preponderant. Nutrient enrichment triggered strong variabilities in dominance and successions among the cyanobacterial group, with maximum dominance (76.34%) exhibited by the Aphanizomenon sp. upon NH addition. Fe enrichment led to the succession of cyanobacteria, Leptolyngbya tenuis, which was below the detectable limit in the control, indicating the role of Fe in its proliferation. Studies on nutrient limitation demonstrated P/NH co-limited ecosystem, with P as the primary and NH, a secondary limiting factor. The nitrate preference index (NORPI = 0.991) shows a high preference for NH while NO constitutes the bulk of the ecosystem TN. Considering the elevated NO concentration, we posit that a shift in the phytoplankton community structure from cyanobacteria to diatoms dominated ecosystem, is expected following Fe depletion and a further stretch on the current ecosystem NH limitation. The study provides useful and first-ever insights for nutrient reduction in the middle Three Gorges Reservoir (TGR) before the onset of the heavy HABs during spring in the Pengxi River.
养分可利用性是促进淡水富营养化和有害藻类水华（HABs）快速扩张的关键人为胁迫因素，正在全球范围内恶化水质并威胁公众健康。在描述生态系统生长限制因素的同时，估算 HABs 群落对昼夜变化中养分的响应，是谨慎进行流域管理的关键。本研究采用营养添加生物测定法，研究了秋季蓝藻对彭溪河外部养分输入的短期变化的响应。结果表明，浮游植物群落结构由蓝藻（相对丰度= 46.20%平衡丰度）主导，其中 Anabaena 和 Aphanizomenon spp. 占主导地位，其次是硅藻，其中 Lindayia bodaniica 占优势。营养富集会引发蓝藻群落在优势度和演替方面的强烈变化，NH 添加时 Aphanizomenon sp. 表现出最大的优势度（76.34%）。Fe 富集会导致蓝藻 Leptolyngbya tenuis 的演替，其在对照中低于检测限，表明 Fe 在其增殖中的作用。对养分限制的研究表明，该系统为 P/NH 共限制，其中 P 为主要限制因子，NH 为次要限制因子。硝酸盐偏好指数（NORPI=0.991）表明对 NH 有很高的偏好，而 NO 构成了生态系统 TN 的大部分。考虑到升高的 NO 浓度，我们假设在彭溪河当前生态系统 NH 限制进一步加剧以及 Fe 耗尽后，浮游植物群落结构将从蓝藻为主转变为以硅藻为主的生态系统。该研究为三峡水库中游在彭溪河春季出现严重 HABs 之前进行养分减排提供了有用的和首次的见解。
