Author:

Keywords:

phytoplankton bloom dynamics, primary nitrite maximum, sea ice edge, southern-ocean, ross sea, primary productivity, nitrification rates, surface waters, austral summer, indian sector, Science & Technology, Life Sciences & Biomedicine, Physical Sciences, Ecology, Marine & Freshwater Biology, Oceanography, Environmental Sciences & Ecology, PHYTOPLANKTON BLOOM DYNAMICS, PRIMARY NITRITE MAXIMUM, SEA ICE EDGE, SOUTHERN-OCEAN, ROSS SEA, PRIMARY PRODUCTIVITY, NITRIFICATION RATES, SURFACE WATERS, AUSTRAL SUMMER, INDIAN SECTOR, 0405 Oceanography, 0602 Ecology, 0608 Zoology, Marine Biology & Hydrobiology, 3103 Ecology, 3109 Zoology, 4102 Ecological applications

Abstract:

Distributions of nitrate and ammonium and corresponding uptake fluxes were investigated in the Scotia-Weddell Confluence area during EPOS LEG 2 (November and December 1988) on board RV 'Polarstern'. In this area a central low-salinity and low-nitrate compartment extends southward from the Scotia Front over 1 to 1.5-degrees-latitude. High ammonium concentrations and marked nitrate depletions indicate an enhanced biological activity in this part of the ocean. By means of the uptake rates, obtained from N-15 incubations, and of nitrate depletion data it is proved that this marginal ice zone ecosystem shifts from predominantly new production based (highest f-ratio 0.83) to regenerated production based (lowest f-ratio 0.30) after some 3 wk. This transition corresponds with the change from a higher diatom presence to a higher flagellate presence in the phytoplankton community. Moreover, it is in agreement with the described sudden termination of export fluxes in the Weddell Sea.