Modified methods for defining the chlorophyll concentration in the sea using submersible fluorimeters - Theoretical and quantitative analysis

The paper analyses the reliability of fluorimetric methods for determining chlorophyll concentrations in the sea using a submersible fluorimeter. To this end, such concentrations were measured with a bbe FluoroProbe spectrofluorimeter as well as standard methods in a range of Baltic basins of different trophic index. This analysis shows that fluorimetrically determined chlorophyll concentrations are usually slightly lower than those obtained with standard methods and that the error increases with rising trophic index. Similar tendencies are observed in relation to measurements carried out with different types of fluorimeters and in different waters. Probably due to the nonlinearity of the relationship between the concentration of chlorophyll a and the intensity of its fluorescence, this can be explained by the changes in the fluorescence quantum yield and package effect function with trophic index. It is therefore recommended that the internal algorithms of fluorimeters be recalibrated in the manner suggested.