Optical parameters of the Black Sea waters: long term variability and present status

Seasonal and long-term variability of the Black sea optical parameters are analyzed using valuable data set from the data bases of Marine Hydrophysical Institute and Institute of Marine Sciences. The drastic decrease of the water transparency was observed during 1986-1992. It coincided with the big changes of the spectral distribution of water optical parameters. The main causes of these changes are eutrophication, influence of biological invader Mnemiopsis leidyi on the sea ecosystem, and the natural 11-years cycle.