INFLUENCE OF BIOTIC FACTORS ON THE HYDROCHEMICAL STRUCTURE OF SURFACE-WATER IN THE POLAR FRONTAL ZONE OF THE ATLANTIC ANTARCTIC

An investigation conducted in a Polar Frontal Zone site (26-40-degrees -W, 48-52-degrees-S) in the spring-summer season of 1988-1989 was foll owed by four smaller surveys. The study of abiotic conditions included measurements of O2, NO3, PO4, SiO2 etc. Smaller-scale surveys conduct ed after the basic survey showed that, due to intensive phytoplankton growth, autotrophic organism were actively consuming nutrients yieldin g high concentrations of chlorophyll 'a' (4.5 mug l-1). Silicate dropp ed from 10-55 muM to less than 2.5 muM, and phosphate from 1.8-2.0 to 0.85 muM. Phytoplankton blooms resulted in a spatial redistribution of abiotic gradient zones and the formation of 'biological' fronts. Thus , the silicate horizontal gradient at such fronts amounted to 7.22 muM per k.