In Situ Measurements of Plankton Biorhythms Using Submersible Holographic Camera

Spectroscopic aspects of underwater digital holography of plankton

Monitoring the parameters and behavior of plankton makes it possible to assess the state of the aquatic ecosystem and detect the beginning of an environmental disaster at an early stage. In this respect, the most informative method for the in situ plankton study is underwater digital holography. This method allows obtaining information on the size, shape, and location of plankton individuals, as well as performing their classification and biotesting according to their behavioral responses using a submersible holographic camera non-invasively, in real time, and in the automatic mode. The monitoring series of the ecosystem functions can be used to assess the state of the ecosystem. One of them is the time series of the concentration of individuals of various plankton taxa in a certain volume. There are characteristic rhythms in the ecosystem function caused by both plankton biorhythms and changes in habitat parameters, as well as their synchronization, whereas a change in this rhythm may serve as an alarm signal for the ecosystem deprivation. By constructing the analogies based on the spectroscopy of atoms and molecules the paper shows the bioindication capabilities of the Fourier spectra of the plankton ecosystem function, built during monitoring measurements using a submersible digital holographic camera. The spectroscopic study of plankton allows determining the pollution in the plankton habitat at early stages. The in situ experimental data suggest that the order and chaos of plankton biocenosis are reflected in the structure of the spectral lines of the ecosystem functions associated with plankton. Various self-oscillatory processes in the biocenosis that regulate the plankton number and rhythm form the basis for plankton spectroscopy, which may be used for bioindication monitoring.

Monitoring Bioindication of Plankton through the Analysis of the Fourier Spectra of the Underwater Digital Holographic Sensor Data

The study presents a bioindication complex and a technology of the experiment based on a submersible digital holographic camera with advanced monitoring capabilities for the study of plankton and its behavioral characteristics in situ. Additional mechanical and software options expand the capabilities of the digital holographic camera, thus making it possible to adapt the depth of the holographing scene to the parameters of the plankton habitat, perform automatic registration of the "zero" frame and automatic calibration, and carry out natural experiments with plankton photostimulation. The paper considers the results of a long-term digital holographic experiment on the biotesting of the water area in Arctic latitudes. It shows additional possibilities arising during the spectral processing of long time series of plankton parameters obtained during monitoring measurements by a submersible digital holographic camera. In particular, information on the rhythmic components of the ecosystem and behavioral characteristics of plankton, which can be used as a marker of the ecosystem well-being disturbance, is thus obtained.