  We find evidence that a certain class of reaction-diffusion systems can
exhibit chemical turbulence equivalent to Nikolaevskii turbulence. The
distinctive characteristic of this type of turbulence is that it results from
the interaction of weakly stable long-wavelength modes and unstable
short-wavelength modes. We indirectly study this class of reaction-diffusion
systems by considering an extended complex Ginzburg-Landau (CGL) equation that
was previously derived from this class of reaction-diffusion systems. First, we
show numerically that the power spectrum of this CGL equation in a particular
regime is qualitatively quite similar to that of the Nikolaevskii equation.
Then, we demonstrate that the Nikolaevskii equation can in fact be obtained
from this CGL equation through a phase reduction procedure applied in the
neighborhood of a codimension-two Turing--Benjamin-Feir point.
