High-resolution, basin-wide chemical data reveal that the Black Sea upper layer possesses distinct chemical features at specific density surfaces, but with some noticeable regional differences in their positions and magnitudes. The nitracline, is consistently established at smaller density surface relative to the phosphocline over the basin; thus, N:P molar ratios appear to be unexpectedly high (40-80) within the upper nutricline, especially in the anticyclonic regions (ACR). The ratio drops to levels of 4-8 at the nitrate mar;ima formed within the base of the main oxycline. Phosphate profiles display a prominent minimum within the suboxic zone of tl le cyclonic regions (CR), which weakens markedly within the coastal regions and rim current. Vertical distributions of chemical ratios have led to valuable information on the relative fluxes in the oxic/anoxic transition zone as well as the quality of data sets from different years
