Mechanism Underlying Flow Velocity and Its Corresponding Influence on the Growth of Euglena gracilis, a Dominant Bloom Species in Reservoirs

Abstract

The effects of hydrodynamics on algae growth have received considerable attention, and flow velocity is one of the most frequently discussed factors. For Euglena gracilis, which aggregates resources and is highly resistant to environmental changes, the mechanism underlying the impact of flow velocity on its growth is poorly understood. Experiments were conducted to examine the response of algae growth to different velocities, and several enzymes were tested to determine their physiological mechanisms. Significant differences in the growth of E. gracilis were found at different flow velocities, and this phenomenon is unique compared to the growth of other algal species. With increasing flow velocity and time, the growth of E. gracilis is gradually inhibited. In particular, we found that the pioneer enzyme is peroxidase (POD) and that the main antioxidant enzyme is catalase (CAT) when E. gracilis experiences flow velocity stress. Hysteresis between total phosphorus (TP) consumption and alkaline phosphatase (AKP) synthesis was observed. Under experimental control conditions, the results indicate that flow velocities above 0.1 m/s may inhibit growth and that E. gracilis prefers a relatively slow or even static flow velocity, and this finding could be beneficial for the control of E. gracilis blooms.

A microscale system for in situ investigation of immobilized microalgal cell resistance against liquid flow in the early inoculation stage

“…As supported by the conclusion of Tan et al (2019), shear stress elevated antioxidant enzyme activity in microalgae whereas lower flow velocity increased the nutrient consumption rate, but it was species-dependent. 44 Distinct algae have different critical flow rates that must be met in order to maximize algal chlorophyll content; however the flow pattern (laminar, transitional, or turbulent) does not have a significant impact on the cell proliferation. 45…”

Reducing the Risk of Benthic Algae Outbreaks by Regulating the Flow Velocity in a Simulated South–North Water Diversion Open Channel

“…The effect of hydrodynamic conditions on algal growth is that a low-flow velocity promotes algal aggregation and attachment [ 16 ], whereas medium-intensity disturbances increase nutrient uptake by algal cells and promote metabolism [ 17 ]. In contrast, high-intensity disturbances inhibit algal growth, nutrient absorption, and cell metabolism [ 18 ]. The hydrodynamic conditions affect changes in algal cell proliferation, morphology, metabolic activity, and nutrient uptake.…”