Storm and floods increase the duration and extent of phosphorus limitation on algal blooms in a tributary of the Three Gorges Reservoir, China
Storm and floods increase the duration and extent of phosphorus limitation on algal blooms in a tributary of the Three Gorges Reservoir, China
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DOI：
10.1016/j.jhydrol.2022.127562
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发表时间：
2022-02
影响因子：
6.4
通讯作者：
Yiping Li;Yanan Huang;Daobin Ji;Y. Cheng;A. S. Nwankwegu;H. Paerl;Chunyan Tang;Zheng-jian Yang
中科院分区：
文献类型：
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作者：
Yiping Li;Yanan Huang;Daobin Ji;Y. Cheng;A. S. Nwankwegu;H. Paerl;Chunyan Tang;Zheng-jian Yang
过多的人为养分输入导致了富营养化和藻类大量繁殖，严重影响了水生生态系统的功能和可持续性，这突出表明需要实施养分管理战略。认为汛期降雨量的增加会影响总氮（TN）：总磷（TP）的化学计量比，从而导致藻类生长的营养限制。为了验证这一概念并探索相应的营养盐管理策略，在三峡水库最大的支流之一香溪湾进行了营养盐添加生物测定。结果表明，营养盐对藻类生长的限制是从氮（N）限制到磷（P）限制。早汛期以氮素限制为主。然而，溶解磷的减少，伴随着增加的TN：TP所造成的极端降雨事件加剧了整个海湾的磷限制。汛期后降雨减少和蓄水过程缓解了磷限制。TN的变化：降雨量增加和洪涝灾害引起的TP可能是主要受外部营养输入影响的水生态系统营养限制转移的主要驱动因素。营养盐稀释和富集试验表明，为限制藻类生长，维持叶绿素含量在30 μg/L以下，TN和TP的浓度阈值分别应控制在0.55 mg/L和0.057 ~ 0.064 mg/L以下。双营养（N & P）的减少需要在整个流域的长期水华缓解。该研究为三峡库区支流营养盐管理策略提供了科学依据，以防治富营养化和减少水华。我们建议，考虑到未来土地利用、人口密度和气候变化的影响，需要长期确定营养限制和营养阈值，以控制藻类生长。
Excessive anthropogenic nutrient input has resulted in eutrophication and algal blooms which have severely impacted the function and sustainability of aquatic ecosystems, underscoring the need to implement nutrient management strategies. It was assumed that the increasing rainfall during flood season would affect the stoichiometric ratio of total nitrogen (TN): total phosphorus (TP), driving the nutrient limitation of algal growth. In order to test this concept and explore corresponding nutrient management strategies, nutrient addition bioassays were carried out in Xiangxi Bay, one of the largest tributaries of the Three Gorges Reservoir (TGR), China. Results indicated that nutrient limitation on algal growth fluctuated from nitrogen (N) to phosphorus (P) limitation. N limitation dominated in the early flood season. However, the reduction of dissolved P, accompanied with an increase of TN: TP caused by an increase in extreme rainfall events intensified P limitation throughout the bay. Then P limitation was alleviated due to the reduction of rainfall and the process of impoundment after the flood season. The variation of TN: TP caused by the increasing of rainfall and flooding could be the main driving factor of the nutrient limitation shift in aquatic ecosystems mainly affected by external nutrient inputs. Nutrient dilution and enrichment bioassays showed that TN and TP concentration thresholds should be targeted at below 0.55 mg/L and 0.057 ∼ 0.064 mg/L respectively, to limit the growth of algae and maintain chlorophyllabelow 30 μg/L. Dual nutrient (N & P) reductions were required for long-term bloom mitigation in the entire basin. This study provided a scientific basis for a nutrient management strategy to combat eutrophication and reduce algal bloom potentials in the tributaries of the TGR. We recommend that long-term determinations of nutrient limitation and nutrient threshold will be needed to control algal growth, considering future anticipated changes in land use, population density and the impacts of climate change.