Study of a hydrodynamic threshold system for controlling dinoflagellate blooms in reservoirs

Yang Song; Lian Shen; Linglei Zhang; Jia Li; Min Chen

doi:10.1016/j.envpol.2021.116822

Study of a hydrodynamic threshold system for controlling dinoflagellate blooms in reservoirs

Environ Pollut. 2021 Jun 1:278:116822. doi: 10.1016/j.envpol.2021.116822. Epub 2021 Feb 25.

Authors

Yang Song¹, Lian Shen², Linglei Zhang³, Jia Li⁴, Min Chen⁴

Affiliations

¹ Institute of Ecology and Environment, State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu, Sichuan, China; Department of Mechanical Engineering and St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN, 55455, USA.
² Department of Mechanical Engineering and St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN, 55455, USA.
³ Institute of Ecology and Environment, State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu, Sichuan, China. Electronic address: zhanglinglei@hotmail.com.
⁴ Institute of Ecology and Environment, State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu, Sichuan, China.

PMID: 33677223
DOI: 10.1016/j.envpol.2021.116822

Abstract

Hydrodynamic conditions often affect the eutrophication process and play a key role in algal growth in reservoirs. A promising approach for controlling algal blooms in reservoirs is to create adverse hydrodynamic conditions by implementing reservoir operation strategies. However, research on this method is still nascent and does not support practical applications due to the lack of quantitative hydrodynamic thresholds. In this paper, field observations of algal growth from April 2015 to August 2016 were conducted, and a three-dimensional (3D) model that couples hydrodynamics and water temperatures for the Zipingpu Reservoir was established. Low flow velocities (V) and low Reynolds numbers (Re) in the Longchi tributary are favorable for dinoflagellate growth and accumulation, which can explain why dinoflagellate blooms are more likely to occur in the tributary. A temperature of 18-22 °C is considered a precondition for Peridiniopsis penardii blooms, suggesting that freshwater dinoflagellate species may prefer lower temperatures than marine dinoflagellate species. Shallow mixing layer depth (Z_mix) is conducive to Peridiniopsis penardii gathering in the upper water layers and promotes growth. The shallow euphotic layer depth (Z_eu) was speculated to promote the dominance of this species by stimulating its heterotrophy and inhibiting other algal autotrophy. Furthermore, a boundary line analysis was introduced to characterize the relationships between algal biomass and hydrodynamic indicators. Thus, the thresholds for V, Re, and Z_mix/Z_eu were determined to be 0.034 m s^-1, 6.7 × 10⁴, and 1.7, respectively. Either accelerating horizontal flow to exceed the thresholds of V and Re or facilitating vertical mixing to exceed the threshold of Z_mix/Z_eu can prevent dinoflagellate blooms. Therefore, the summarized hydrodynamic threshold system is suggested to be an effective standard for controlling dinoflagellate blooms in the reservoir. Moreover, this study can provide a useful reference for understanding the mechanism of freshwater dinoflagellate blooms.

Keywords: Boundary line method; Dinoflagellate blooms; Flow characteristics; Hydrodynamic threshold system; Thermal structure; Vertical mixing and light structure.

MeSH terms

Dinoflagellida*
Eutrophication
Fresh Water
Hydrodynamics*
Temperature