蓝藻水华及其降解对沉积物-水微界面的影响

模拟研究了不同条件下,蓝藻水华及其降解过程对沉积物-水微界面的影响.采用丙酮法测定水体中叶绿素质量浓度,溶解氧微电极测定界面溶解氧质量浓度,毫米级分层测定沉积物中营养盐与金属元素的垂直分布.结果表明,蓝藻水华及其降解过程改变了界面附近溶解氧环境和表层约3 mm深沉积物中营养盐与金属元素的垂直分布.扰动在蓝藻水华降解过程和C、P营养盐与Fe、Ca、Mg、Al和K等金属元素的早期成岩过程中起着重要作用.遮光加速了蓝藻降解,并且削弱了扰动的影响.无处理对照组沉积物表面出现了一层底栖藻,底栖藻的光合作用产生了氧气,造成表层1 mm沉积物中大部分营养盐与金属元素质量浓度和处理组间的显著性差异.相关分析结果表明,沉积物中P的垂直分布与Mn显著相关,其次是C.高分辨率研究结果可见,蓝藻水华及其降解过程在毫米级厚度内即对沉积物-水界面产生了影响.

Effects of Algal Blooms and Their Degradation on the Sediment-water Micro-interface

Effects of algal blooms and their degradation on the sediment-water micro-interface under conditions of disturbance and darkness were investigated. The concentration of chlorophyll a in water was determined via the acetone method, profiles of oxygen near the interface were measured using a microelectrode, and profiles of nutrients and metals in sediments were measured at the millimeter level. The results showed that algal bloom degradation at the sediment-water micro-interface decreased the concentration of oxygen and affected nutrient and metal profiles, at depths over approximately 3 mm. Disturbance played an important role in algal bloom degradation and early diagenesis processes of nutrients, such as C and P, and metals, such as Fe, Ca, Mg, Al, and K. Darkness sped up algal bloom degradation and reduced the influence of disturbance. Under control conditions of no disturbance nor algae, and supplied with enough light, a layer of benthic algae appeared at the sediment surface, whose photosynthesis produced oxygen and greatly changed the microenvironment. This brought about significant differences in the concentrations of nearly all nutrients and metals in the surficial sediment compared with those of other treatments. Correlation analyses showed that the vertical variability of sediment P concentration was most strongly related to sediment Mn, followed by sediment C. The results of this high-resolution research showed that algal bloom degradation had an effect on the sediment-water micro-interface at the millimeter level.