4. Conclusions
The fluorescence parameters of Chl a and CDOM, which provide information about the relative concentrations of the main seawater constituents, could be calculated following analysis of laser-induced fluorescence (LIF) spectra of different seawater masses. The content of these constituents affects the radiative energy flux exchange between sea and atmosphere, which, in turn, governs numerous, environmentally significant biophysical processes and determines the biophysical status of waters. The analytical results highlighted changes in the fluorescence properties of the seawater constituents, enabling maps of their spatial distribution in different areas of Baltic and Nordic Seas to be constructed.
Spatial distribution patterns not only of Chl a, but also of CDOM can be discerned. Rivers constitute the principal source of CDOM in the sea, but another relevant source is partly decomposed phytoplankton, which exists mainly in areas where intensive blooms of phytoplankton have taken place. The relationships between the contents of CDOM and Chl a (their fluorescence parameters) enabled waters with different bio-optical properties to be distinguished and a link between fluorescence parameters and CDOM sources in the seawaters to be established.
The specific bio-optical status of seawaters can be determined from the correlation of the linear relationships between the fluorescence parameters of Chl a and CDOM. A positive correlation for a given body of water indicates the presence of the same sources of CDOM runoff.
The results obtained in the Baltic Sea allow certain inferences to be drawn from the positive correlations obtained between the fluorescence factors of Chl a and CDOM: they exist only for local waters and are variable in time. During the spring algal blooms, the bio-optical properties of the entire southern Baltic are similar. In the other seasons, however, the dominant influence of the Vistula river runoff and mixing processes combine to produce the homogeneous fluorescence properties of Gulf of Gdańsk waters.
Similar measurements were carried out in Nordic Seas, where a positive correlation was found for the open waters; these can be classified as Case 1 waters.
Answers to all your Biology Questions
