Short-term effect of cadmium on the motility of three flagellated algal species

The present work aims to develop a fast and reliable procedure for motility analysis of a short-term effect of heavy metal cadmium on the algal cell response in laboratory conditions. Three unicellular motile species similar in cell length, while differing in the cell wall and the flagellar system are used as model algae. We quantitatively characterise motility in terms of swimming speed and search radius following addition of 1 mg Cd L −1 . Both swimming speed and search radius determined in control algal cultures reflect morphological features of the corresponding flagellated system. After 1 h of cell exposure to a toxic concentration of cadmium, a statistically significant decrease in swimming speed is determined with predominant erratic cell movement on the spot in all examined cultures. After 3 h of cell exposure to cadmium, swimming speed in most of the examined cell cultures recovered close to the control value, indicating quick cell adaptation to elevated cadmium concentration. The results support the implementation of swimming speed and search radius as motility parameters for direct screening of cell physiological state, which is applicable to ecotoxicological studies providing insight into the mechanism of cell adaptation under stress, as well as a better understanding of the spatial distribution of algal cells in aquatic systems.