Reviews of influences from hydrodynamic conditions on algae

Hydrodynamic conditions are important factors to influence eutrophication and water bloom.It is of significance for the eutrophication control to study effects of hydrodynamic conditions on algal growth and algal species change.This paper reviewed the most recent studies on algal growth influences and species changes due to flow velocity or turbulence status and discussed the effects of hydrodynamic conditions on algae.The influences of hydrodynamic conditions on algal growth include 2 aspects which were flow velocity and flow regime.Small-scale fluid motion or low flow velocity were mostly proved to be good for algal growth and aggre-gation regardless of monoculture or mixed culture.The increases in flow velocity induced initial increases and then subsequent de-creases in the Chla concentration.The critical velocities for various algae were not the same.Algal growth was inhibited when the level of turbulence in the water was increased.The inhibitory effect was not correlated with flow regime(laminar,transitional,or turbulent).Changes of flow regime led to the changes of shear stress,which caused different responses in various algae.The changes of algal population structure resulted from hydraulic condition changes mostly presented as dominant species shifting caused by in-tensive water mixing.The mechanisms of all these influences were primarily changes in the luminous intensity,cell length,nutrient transport and predatory behavior.Based on the advances in the current research,it is recommended that more studies focused on the actual inhibitory effects from hydrodynamic conditions,the lowest influencing level of turbulence and its mechanisms be conducted.