Dynamic criterion for the formation of surface water-blooms

Surface water-blooms(SWBs) is usually explained as a buoyant migration of blue-green algae to the watersurface under the conditionsof reduced turbulence.Wind-induced turbulentmixing can causeconsiderable heterogeneity in the vertical concentration distribution of algal cells. There exists a criterion below whichcell buoyancy can overcomethe turbulentmixing. Former researchersregarded a certain wind speed as this criterion, but this wind speed differs in value. In thisresearch, we propose a new criterion, nondimensional entrainment number (En), whichrepresents the ratio of the intrinsic velocity of algal cells relative to the characteristic velocity of wind-inducedmixing. Observation inTaihu Lake demonstrates thatthis new criterion is more suitable for the description of hydrodynamic effect on the formation ofsurface water-blooms.