Particle fluxes during austral spring and summer in the southern Ross Sea, Antarctica

Abstract

The flux of particles from the euphotic zone through 200 m was investigated on the Ross Sea continental shelf during two cruises, the first in November‐December 1994 and the second in December 1995 and January 1996. An assessment of surface layer phytoplankton biomass and productivity was made simultaneously. Particle flux was measured using floating sediment traps whose collection efficiency was assessed rigorously. Phytoplankton biomass and productivity increased rapidly in November‐December, and biomass was maximal in mid‐December. Thereafter productivity appeared to decline substantially. Biomass declined as well, but not as rapidly as productivity. Vertical flux rates were low early in the bloom period, averaging 457 mg m−2 d−1, but increased markedly in late December and January (mean = 1160 mg m−2 d−1). Daily losses due to vertical flux represented only 2.3% of the surface layer particulate organic carbon standing stock. Measured particle fluxes were greater than those observed previously, and this is attributed to the period and depths sampled as well as to the care taken to ensure accuracy of sample collection. As in other regions, vertical flux of biogenic material is coupled with surface layer production and biomass. In our study area, however, a distinct temporal lag is introduced between surface production and flux at depth as a result of the temporal characteristics of the dominant mechanism generating large particles (aggregation) as well as the characteristic species of the region (Phaeocystis antarctica).