Saint Louis University, Department of Earth and Atmospheric Sciences, O'Neil Hall, 3642 Lindell Blvd, Saint Louis, MO 63108, USA.
University of Central Florida, Department of Biology, Biological Sciences Bldg., 4110 Libra Drive, Orlando, FL 32816, USA.
Sci Total Environ. 2017 Mar 1;581-582:589-600. doi: 10.1016/j.scitotenv.2016.12.168. Epub 2017 Jan 6.
Harmful algal blooms are increasingly common in aquatic ecosystems and have been linked to runoff from agricultural land. This study investigated the internal nutrient (i.e., phosphorus (P) and nitrogen (N)) dynamics of a eutrophic reservoir in the Midwestern United States to constrain the potential for sedimentary nutrients to stimulate harmful algal blooms. The spatial distribution of nutrients in the water column (soluble reactive P (SRP), nitrate/nitrite-N (NO-N), and ammonium-N (NH-N)) and sediments (total P, total carbon (C), total N, and organic matter (OM)) were quantified and mapped. Water column nutrients varied spatially and temporally, with generally higher concentrations near the dam wall during normal lake levels. The upper portion of the lake, near the inlet, was sampled during a flood event and had overall higher nutrient concentrations and lower chlorophyll levels compared to normal lake level samples. Mean sedimentary total P (936mg/kg) was ~30% higher in the reservoir than the surrounding upland soils, with the highest concentrations near the dam wall (1661mg/kg) and a significant positive correlation found between sedimentary total P, total C, and OM. Additionally, 15 intact sediment cores were manipulated ex situ to examine mechanisms of nutrient flux across the sediment-water interface (SWI) that may trigger algal blooms. Core treatment conditions included advection (i.e., simulating potential nutrient fluxes during wind events through sediment resuspension) and diffusion. Core experiments indicated both advective and diffusive conditions at the SWI may trigger the flux of nutrients important for algal growth from lake sediments, with diffusion contributing both N and P to the water column, while intense advection increased water column N, but decreased P. Release of P to the water column may be more diffusion-driven than advection-driven, whereas N release to the water column appears to be both diffusion- and advection-driven.
富营养化水库中沉积物养分对水华爆发的潜在激发作用研究
水生生态系统中有害藻类水华的发生日益频繁，且与农业土地的径流有关。本研究调查了美国中西部富营养化水库的内部养分（即磷（P）和氮（N））动态，以限制沉积物养分激发有害藻类水华的潜力。定量和绘制了水柱（可溶解性反应磷（SRP）、硝酸盐/亚硝酸盐-N（NO-N）和氨氮（NH-N））和沉积物（总磷、总碳（C）、总氮和有机质（OM））中养分的空间分布。水柱中的养分具有时空变化，在正常湖水位时，大坝壁附近的浓度通常较高。在洪水事件期间，对靠近入水口的湖泊上部进行了采样，与正常湖水位样本相比，其养分浓度总体较高，叶绿素水平较低。水库中的沉积物总磷（936mg/kg）比周围高地土壤高出约 30%，大坝壁附近的浓度最高（1661mg/kg），且沉积物总磷、总 C 和 OM 之间存在显著的正相关关系。此外，还对 15 个完整的沉积物岩芯进行了体外处理，以研究可能引发藻类水华的营养物质在沉积水界面（SWI）上的通量机制。岩芯处理条件包括平流（即，通过泥沙再悬浮模拟风事件期间潜在的养分通量）和扩散。岩芯实验表明，SWI 处的平流和扩散条件都可能触发湖泊沉积物中对藻类生长重要的养分通量，其中扩散将 N 和 P 都输送到水柱中，而强烈的平流增加了水柱中的 N，但降低了 P。P 向水柱中的释放可能比平流驱动更受扩散驱动，而 N 向水柱中的释放似乎既受扩散驱动又受平流驱动。
