Analysis of swimming trajectories in Daphnia similis as an environmental impact assessment tool

Abstract

Toxicity tests with daphnids are important tools in the environmental impact assessment of aquatic ecosystems. The aim of this study was to characterize the swimming paths of Daphnia similis in response to two concentrations of the reference substance potassium chloride (KCl), as an additional expedite tool in evaluating the effects of contaminants. Bidimensional trajectory coordinates were obtained with image acquisition and processing methods and used to calculate the following metrics of D. similis behavior: mean swimming speed, hop rate, fractal dimension, and vertical occupancy. The swimming speed, hop rate and fractal dimension for the control group were significantly different from the KCl treatment at the higher concentration. Conversely, the vertical occupancy did not differ between the experimental conditions. The results of this investigation validate the use of behavioral analysis as a rapid and reliable approach to evaluate water contamination, aiding in early warning detection of water quality issues. The method can be further refined through the integration of machine learning applications in video tracking.