Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing, 400044, China.
Biomass Energy Technology Research Center, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China.
Water Res. 2019 Feb 1;149:251-262. doi: 10.1016/j.watres.2018.11.003. Epub 2018 Nov 5.
The effect of turbulence on phytoplankton growth has been widely studied; however, its effects with respects to suspended particulate matter (SPM) on the development of phytoplankton communities and the behavioral responses of phytoplankton to turbulence and SPM are poorly understood. Here, an approximately homogeneous turbulence simulation system (AHTS, mainly consisting of an oscillating-grid apparatus) was established to gain insight into the mechanisms underlying phytoplankton community responses in turbid, well-mixed waters. The results revealed that maintaining the turbulence dissipation rates (Ɛ) of 2.25 × 10 and 1.80 × 10 m/s caused significant reductions in algal density, and the effects could be substantially enhanced when 500 mg/L of SPM were added before day 12. In contrast to the constant decrease of algal density for the Ɛ of 2.25 × 10 m/s, a dramatic increase in the phytoplankton density occurred after 16 days of incubation for a Ɛ of 1.80 × 10 m/s, irrespective of SPM. Addition of SPM in the Ɛ of 1.80 × 10 m/s treatments did not considerably affect the algal density profile compared to that without SPM, of which unicellular algae decreased and colonial algae dominated the phytoplankton community. On the other hand, the phytoplankton can regulate the SPM properties. During the 18 days' coincubation, extracellular polymeric substances (EPS) released from algal cells induced larger particle sizes and round surfaces of SPM, which can reduce the damage received to algal cells. Here we demonstrated that the phytoplankton communities could actively counteract the effects of turbulence + SPM and adapt the couple stress, jointly through the release of EPS, the modification of SPM surface properties and the conversion of their assemblage pattern, thereby contributing to rebalance the ecosystem. These findings highlight the strategies employed during the reconstruction of phytoplankton under the dual effects of turbulence and SPM for the first time, consequently enabling the forecasting of the dominant species of phytoplankton in turbulent waters.
湍流对浮游植物生长的影响已得到广泛研究；然而，关于悬浮颗粒物（SPM）对浮游植物群落发展的影响以及浮游植物对湍流和 SPM 的行为反应，人们知之甚少。在这里，建立了一个近似均匀的湍流模拟系统（AHTS，主要由振荡网格装置组成），以深入了解混浊、充分混合的水中浮游植物群落响应的机制。结果表明，维持湍流耗散率（Ɛ）为 2.25×10 和 1.80×10 m/s 会导致藻类密度显著降低，当在第 12 天之前添加 500mg/L 的 SPM 时，这种影响可以大大增强。与 2.25×10 m/s 的Ɛ 导致藻类密度持续下降相反，对于 1.80×10 m/s 的Ɛ，在孵育 16 天后浮游植物密度会急剧增加，无论是否添加 SPM。与不添加 SPM 的处理相比，在 1.80×10 m/s 的Ɛ 处理中添加 SPM 对藻类密度分布没有显著影响，其中单细胞藻类减少，而群体藻类则主导浮游植物群落。另一方面，浮游植物可以调节 SPM 的性质。在 18 天的共培养期间，藻类细胞释放的细胞外聚合物物质（EPS）会导致 SPM 的粒径变大且表面变圆，从而减少藻类细胞受到的损伤。在这里，我们证明了浮游植物群落可以通过释放 EPS、改变 SPM 表面性质以及改变其组合模式来积极应对湍流+SPM 的影响并适应耦合应力，从而有助于重新平衡生态系统。这些发现首次强调了在湍流和 SPM 的双重影响下，浮游植物重建时所采用的策略，从而能够预测湍流水中浮游植物的优势种。
