[The dependence of fluorescence in phytoplankton on external influences]

Phytoplankton is the main source of oxygen and the primary link in the food chain for water objects; it plays an important role in their ecological state. The influence of environment parameters on intensity of fluorescence is not considered when measuring concentration by a fluorescence method. In this work the dependence between fluorescence of chlorophyll a contained in phytoplankton cells and the water temperature and illuminating intensity is theoretically and experimentally proved. The formula for a coefficient of proportionality which allows calculating concentration of chlorophyll a is offered taking into account environment parameters. The use of the coefficient calculated in this study allows reducing an error when chlorophyll a concentration is measured by the fluorescence method. Distributions of the phytoplankton chlorophyll concentration in depth calculated with the use of a conventional technique and the coefficient obtained are shown. Phytoplankton fluorescence was measured by a fibro-optic spectrometer in the water area of the Peter Velikiy Bay in September-October, 2013.