Civil Engineering Program, College of Engineering & Computer Science, Arkansas State University, AR 72467, United States.
Oak Ridge Institute for Science and Education at the United States Environmental Protection Agency's Office of Research and Development, Oak Ridge, TN 37830, United States.
Sci Total Environ. 2024 Dec 1;954:175067. doi: 10.1016/j.scitotenv.2024.175067. Epub 2024 Aug 5.
Phytoplankton overgrowth, which characterizes the eutrophication or trophic status of surface water bodies, threatens ecosystems and public health. Quantitative polymerase chain reaction (qPCR) is promising for assessing the abundance and community composition of phytoplankton. However, applications of qPCR to indicate eutrophication and trophic status, especially in lotic systems, have yet to be comprehensively evaluated. For the first time, this study correlates qPCR-based phytoplankton abundance with chlorophyll a (the most widely used indicator of eutrophication and trophic status) in multiple freshwater rivers. From early summer to late fall in 2017, 2018, and 2019, we evaluated phytoplankton, chlorophyll a, pheophytin a, and the Trophic Level Index (TLI) in twelve large freshwater rivers in three regions (western, midcontinent, and eastern) in the United States. qPCR-based phytoplankton abundance had positive allometric correlations with chlorophyll a concentration (adjusted R = 0.5437, p-value < 0.001), pheophytin a concentration (adjusted R = 0.3378, p-value <0.001), and TLI (adjusted R = 0.4789, p-value < 0.001). Thus, a greater phytoplankton abundance suggests a higher trophic status. This work also presents the numerical values of qPCR-based phytoplankton abundance defining the boundaries among trophic statuses (e.g., oligotrophic, mesotrophic, and eutrophic) of freshwater rivers. The sampling sites in the midcontinent rivers were more eutrophic because they had significantly higher chlorophyll a concentrations, pheophytin a concentrations, and TLI values than the sites in the western and eastern rivers. The higher phytoplankton abundance at the midcontinent sites confirmed their higher trophic status. By linking qPCR-based phytoplankton abundance to chlorophyll a, this study demonstrates that qPCR is a promising avenue to investigate the population dynamics of phytoplankton and the trophic status (or eutrophication) of freshwater rivers.
浮游植物过度生长是地表水富营养化或营养状态的特征，它威胁着生态系统和公众健康。定量聚合酶链反应（qPCR）是评估浮游植物丰度和群落组成的有前途的方法。然而，qPCR 用于指示富营养化和营养状态的应用，特别是在流动系统中，尚未得到全面评估。本研究首次将基于 qPCR 的浮游植物丰度与叶绿素 a（最广泛用于指示富营养化和营养状态的指标）相关联，以评估美国三个地区（西部、中西部和东部）的 12 条大型淡水河流。在 2017 年、2018 年和 2019 年的初夏至深秋期间，我们评估了美国三个地区（西部、中西部和东部）的 12 条大型淡水河流中的浮游植物、叶绿素 a、脱镁叶绿素 a 和营养水平指数（TLI）。基于 qPCR 的浮游植物丰度与叶绿素 a 浓度呈正异速相关（调整后的 R=0.5437，p 值<0.001），与脱镁叶绿素 a 浓度（调整后的 R=0.3378，p 值<0.001）和 TLI（调整后的 R=0.4789，p 值<0.001）呈正异速相关。因此，浮游植物丰度的增加表明营养状态较高。这项工作还提供了基于 qPCR 的浮游植物丰度的数值，这些数值定义了淡水河流营养状态（如贫营养、中营养和富营养）之间的界限。中西部河流的采样点由于叶绿素 a 浓度、脱镁叶绿素 a 浓度和 TLI 值显著高于西部和东部河流的采样点，因此富营养化程度更高。中西部地区较高的浮游植物丰度证实了它们较高的营养状态。本研究通过将基于 qPCR 的浮游植物丰度与叶绿素 a 相关联，表明 qPCR 是一种很有前途的方法，可以用来研究浮游植物的种群动态和淡水河流的营养状态（或富营养化）。
