Determination of rhythmic patterns of pelagic community functioning by the Fourier transform method

The change in the luminescence intensity of the pelagic community in coastal waters on the south-western shelf of the Crimea is considered. It was found that the increases and decreases in the luminescence intensity of hydrobiont communities associated with the functioning of the pelagic system were periodically repeated at the same time. It was noted that the biomass of luminous organisms closely correlated with the biomass of plankton and other inhabitants of the pelagic zone, including commercial pelagic fish species. Therefore the intensity of the luminescence of aquatic organisms is a very important information characteristic of biological processes associated with the life of marine communities. Measurements of the luminescence intensity of the pelagic community can be carried out by high-speed biophysical devices in natural conditions without disturbing the structure and interspecific relationships of hydrobiont communities. Using the Fourier transform method, it was possible to find the parameters of the main biological rhythms of plankton communities that lead to a change in the intensity of the luminescence of hydrobionts. It was shown that the change in the intensity of the luminescence of organisms with a period of 14 hours characterized the circadian rhythms of the light and dark periods. Changes in the intensity of the luminescence of organisms with a period of 4.7 and 2.8 hours are due to the ultradian endogenous rhythms of the pelagic community associated with the intensity of cell division of phytoplankton and the rate of their eating by zooplankton. Graphs of changes in the intensity of the luminescence of organisms in the dark, constructed according to the found model, as well as experimental data and errors in their determination are given. Calculations showed that the correlation coefficients between the measured values of the luminescence intensity of organisms and those calculated using the obtained mathematical model was r = 0.906, taking into account the influence of the three main biological rhythms, This confirms the correctness of the accepted propositions.