SMALL-SCALE PLANKTON PATCHINESS IN THE BLACK-SEA EUPHOTIC LAYER

Small-scale horizontal heterogeneites or patches of bioluminescence in tensity and sound volume back scattering strength (SVBS) were studied in the central part of the Black Sea in October, 1989. Bathyphotometri c casts and measurements of SVBS, were taken every 3 minutes in the su rface layer (0-20 m) over a period of several hours from a drifting ve ssel. Casts were accompanied by temperature profiles and zooplankton s ampling. Measurements were carried out during the day and night period s. From adaptive spectral analysis it was shown that the horizontal di mensions of the bioluminescent and SVBS heterogeneities were between 7 5 to 1500 m and 20 to 443 m respectively. In the case of zooplankton b iomass the dimensions were 85 to 818 m and 80 to 1800 m for the temper ature field. Physical and dynamical factors dominate in the formation of small-scale spatial heterogeneity of the studied fields. Biological factors, such as diel vertical migrations, trophic interactions etc. will also contribute to the formation of patches at night.