Positioning of Aquatic Microorganisms in Response to Visible Light and Simulated Solar Uv‐b Irradiation

Three species of protozoans and two crustaceans were irradiated with simulated solar ultraviolet radiation to investigate their ability to detect and avoid UV‐B (320–280 nm). Horizontal and vertical movements to sheltered areas by these organisms suggest that UV‐B is an important environmental factor. UV‐B survival curves were determined which indicated the resistance for each organism studied. The tolerance correlated well with the positioning behavior (i.e. sensitive organisms avoided exposure by moving into sheltered areas whereas the more resistant organisms showed a less pronounced avoidance).