Provisional symposium proceedings

QUALITY OF ESTONIAN COASTAL WATERS BY UNDERWATER OPTICAL MEASUREMENTS Victor Alari, Ants Erm, Germo Väli, Inga Lips and Urmas Lips Marine Systems Institute at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn, Estonia ants@phys.sea.ee Underwater irradiation profiles of the Baltic Sea near the Estonian north and north western coast were measured in the spring and summer 2007. The vertical profiles of downwelling and scalar irradiance in the PAR region were measured in situ on the sea using a frame completed with two planar and a spherical PAR sensors. The measuring system allows calculate as the mean attenuation coefficients of a water column (Kd and Ko respectively) as well the depth profiles Kd(z) and Ko(z). These coefficients, e.g. optical density of the sea water, were varying from 0.13 m (Tallinn-Helsinki line, May) up to 0.75 m (Tallinn Bay, April). As an example some measurements’ series are shown in the figure 1. Fig.1. Variation of attenuation coefficients on Tallinn – Helsinki shipline in the spring 2007. It is seen, that the optical quality of water was much better in May compared to April 2007. Also, it is seen, that expecting the stations immediately near port and road, the Gulf of Finland was quite clear, especially in May. Some increase of optical density towards the Finnish coast could be mentioned also. Many of such cross-sections were made in the spring-summer period of 2007. For example a correlation between the water depth and optical density was followed on the shallows near Hiiumaa. US/EU-Baltic International Symposium 2008 Additionally the water transparency was estimated using the Secchi disk, profiles of chlorophyll were recorded with a fluorimeter, “spectrometric” attenuation coefficient spectra (c*λ), concentrations of chlorophyll a, suspended matter and yellow substance were determined from water samples in the laboratory. This study was supported by the Estonian Science Foundation (Grant No. 7000). The authors are thankful to Dr. Liis Sipelgas for the help with laboratory data. US/EU-Baltic International Symposium 2008 SEATRACK WEB FORECASTS AND BACKTRACKING OF OIL SPILLS AN EFFICIENT TOOL TO FIND ILLEGAL SPILLS USING AIS