Abstract
The purpose of this work is to show the possibilities of using the characteristics of the bioluininescent fields to monitor the marine planktonic communities. The data bank contains 3500 vertical casts of bioluminescent potential and near 1000 samples of the planktonic organisms obtained at 500 oceanographic stations executed in 21 expedition to the Mediterranean Sea basin in 1970-1995. Studies were carried in different seasons in the Mediterranean and the Black Seas where different trophic conditions and considerably different species composition and abundance occurred in the phytoplankton. There are of course differences between abundance of various dinoflagellates and an intensity of measurement of bioluminescence, but the main features of these appeared to be similar, the intensity of bioluminescence increased in proportion to their number and physiological state Seasonal changes are also well developed and mostly in the Black Sea. Two intensive periods of bioluminescence were recorded, one in May-June and the other one. more intensive, in October-November The bioluininescent potential was achieving 1.4 10-2 microwatt cm-2 1-3, which exceeded minimum numbers in February 500 times. Seasonal cycles arc weakly developed in the oligotrophy regions of the Mediterranean Sea: differences of the bioluininescent potential between summer and winter periods achieve 3.5 times only. Macroscale trends of bioluminescence changes within the Mediterranean basin are comparable with that of the plankton spatial distribution. General trend of bioluminescence increase, from the Aegean Sea towards the west and from Algerian coast to Spain, was evaluated on the scale of the whole basin. Bioluminescence in the central part of the Black Sea is 3 times weaker than that in the Alboran Sea. However, it is one order higher than that in the central part of the Mediterranean Sea. As we have stated there are regions of «clean» and «polluted» waters in both neritic and open sea waters. For example, in the Mediterranean Sea the sentral regions of the Alboran. Ionian and Aegean Seas, and the central part of the western gyre and Karadag marine reserve of the Black Sea were all considered to have relatively good water quality while the regions of the intensive shipping (straits, southern part of the Ionian Sea. near-Bosphorus region. Black Sea north-western part) and densely inhabited riparian zones (Crimean southern coast) were considered to be regions of «ecological risk». There are considerable differences between the parameters of the regression lines from the studied regions. For example, to obtain the same bioluminescence intensity in the 0-100 m layer, the quantity of dinoflagellates in polluted regions of the Mediterranean Sea would have been twice as abundant as those from «clean» waters. Similarly the numbers of bioluininescent algae in the Black Sea would have increased 3-4 times to obtain the same bioluininescent intensity. As the anthropogenic pressure in the Black Sea is higer. due to the population density in the river drainage areas and to the low water exchange the differences are more apparent. It can be presumed, that an organism’s metabolic state (and hence its bioluminescence) could serve as an indicator for the levels of pollution in the environment.
Published Version
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