  It is shown that nonlocal interactions determine energy spectrum in isotropic
turbulence at small Reynolds numbers. It is also shown that for moderate
Reynolds numbers the bottleneck effect is determined by the same nonlocal
interactions. Role of the large and small scales covariance at the nonlocal
interactions and in energy balance has been investigated. A possible
hydrodynamic mechanism of the nonlocal solution instability at large scales has
been briefly discussed. A quantitative relationship between effective strain of
the nonlocal interactions and viscosity has been found. All results are
supported by comparison with the data of experiments and numerical simulations.
