Abstract
Delayed luminescence is the phenomenon of long-lived emission of light by living plants and cyanobacteria after being illuminated with light and put into darkness. This study presents uses of this phenomenon as a tool for monitoring the chlorophyll a concentration in phytoplankton. The luminescence method was used on natural phytoplankton from the surface waters in tributaries supplying Lake Miedwie and compared with the commonly used spectrophotometric method of determining chlorophyll a concentrations.