Analyzing a large data base of high-resolution three-dimensional direct numerical simulations of decaying rotating stratified flows, we show that anomalous mixing and dissipation, marked anisotropy, and strong intermittency are all observed simultaneously in an intermediate regime of parameters in which both waves and eddies interact efficiently nonlinearly. A critical behavior governed by the stratification occurs at Richardson numbers of order unity, close to the linear shear instability threshold, and with an accumulation of data points in its vicinity. This confirms the central dynamical role, in such turbulent flows, of strong large-scale intermittency in the vertical velocity and temperature fluctuations, as well as for their gradients, as an adjustment mechanism of the energy transfer in the presence of strong waves. 1 arXiv:1906.04302v1 [physics.flu-dyn] 10 Jun 2019 I. INTRODUCTION, EQUATIONS AND DIAGNOSTICS The atmosphere and the ocean are both known for their large-scale intermittency, with strong non-Gaussian wings of the Probability Distribution Functions (PDFs) of the velocity and temperature fields, as observed in the nocturnal Planetary Boundary Layer 1 , and with strong spatial and temporal variations of the rate of kinetic energy dissipation, as for example in oceanic ridges 2 . Such large-scale intermittency is also found in high-resolution Direct Numerical Simulations (DNS) of stratified flows, in the presence or not of rotation 3,4 , with a direct correlation to high levels of dissipation, as observed for example in the vicinity of the Hawaiian ridge 5 . However, isotropy is classically assumed when estimating energy dissipation of turbulent flows, from laboratory experiments to oceanic measurements, and yet it has been known for a long time that small-scale isotropy recovers slowly in terms of the controlling parameter, such as in wakes, boundary layers, and pipe or shear flows.A lack of isotropy can be associated with intermittency, and with the long-range interactions between large-scale coherent structures and small-scale dissipative eddies 6 . In the purely rotating case, vertical Taylor columns form and, using particle image velocimetry, space-time dependent anisotropy has been shown to be important 7 . In the case of pure stratification, its role on small-scale anisotropy was studied experimentally in detail in 8 .At low Reynolds number, the ratio of stream-wise strain rates of the horizontal and vertical velocity increases with Froude number. Spectral data and dissipation data are mostly stream-wise anisotropic because of the shear, on top of the anisotropy induced by the vertical direction of stratification 9 . The vertical integral length scale does not grow, contrary to its horizontal counterpart 10 , and vertical scales are strongly intermittent.Different components of the energy dissipation tensor have been evaluated, for purely stably stratified flows, as a function of governing parameters (e.g. 11-14 and references therein), and a slow return to isotropy is found only for rather...