Physical and biological processes at the subtropical convergence in the south-west Indian ocean

摘要

A detailed hydrographic and biological survey was conducted in the region of the Subtropical Convergence in the Indian sector of the Southern Ocean in April 2007. Hydrographic data revealed that the subsurface expression of the Subtropical Convergence (at 200 m), marked by the 10 degrees C isotherm, appeared to meander considerably between 41*S and 42'15'S. Total surface chlorophyll-a concentration was low and ranged from 0.03 to 0.42 mu g l(-1) and was always dominated by the pico-( 0.05). The zooplankton community was dominated, numerically and by biomass, by mesozooplankton comprising mainly copepods of the genera, Oithona, Paraeuchaeta, Pleuromamma, Calanus and Clausocalanus. An exception was recorded at those stations in the region of the front where the tunicate, Salpa thompsoni, dominated the total zooplankton biomass.