The influence of an RF pump wave on the spectral electric field fluctuation density and the value of the electromagnetic wave energy density, which is absorbed in the presence of parametric instabilities, is investigated. The RF field power which is absorbed in the plasma is estimated near the threshold of the decay instability. It is shown that the absorbed power increases anomalously as ln(Eth,12/E02-1) for the decay of pump wave into lower hybrid and ion-acoustic waves and as (Eth,22/E02-1)-1/2 for the decay of pump wave into lower hybrid wave and ion quasimode (Eth,1 and Eth,2 are the threshold electric field strength relatively to the excitation of the instabilities which are under consideration and E0 is the pump field strength).