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Abundance and grazing impacts of krill, salps and herbivorous copepods were investigated in Antarctic waters along the 140°E meridian, south of Australia, during the summers of 2002 and 2003. Noah of the Southern Boundary of the Antarctic Circumpolar Current (SB-ACC), macrozooplankton comprised species of Salpa thompsoni and large herbivorous copepods, while the area south of the SB-ACC was numerically dominated by Euphausia superba or E. crystallorophias. North of the SB-ACC, the estimate of grazing impact revealed that krill, salps and copepods, Calanoides acutus, Calanus propinquus, Rhincalanus gigas and Metridia gerlachei, are able to remove a maximum of 37% of the total phytoplankton standing stock in early to midsummer, but grazing is negligible in late summer. The high grazing impact is attributed to the relatively high zooplankton abundance and low phytoplankton abundance. South of the SB-ACC, overall daily grazing impact of the three zooplankton groups was low and did not exceed 6% of the total phytoplankton standing stock throughout the investigation period. Present results indicate that the contribution of krill, salps and copepods varies seasonally as well as regionally across the SB-ACC. It seems that the carbon transport from surface to deep water by macro- and mesozooplankton in summer in this area is relatively large north of the SB-ACC but small south of the SB-ACC. [ABSTRACT FROM AUTHOR]

Inter-annual variability in chlorophyll a (chl a) and sea-ice concentration in the Antarctic Divergence (AD) region near 140°E was examined using satellite sensor data in order to derive a quantitative relationship between the two. Sea-viewing Wide Field-of-view Sensor (SeaWiFS) derived chl a and Special Sensor Microwave/Imager (SSM/1) derived sea-ice concentration data during 1997–2003 were analysed. Mean chl a concentration south of 64 S during the period between September and April (from austral spring to autumn) of each year was calculated. The mean chl a in 2001/2002 was extremely high (1.08 mg m-3) within the six periods between 1997/1998 and 2002/2003. Simply integrated indices on sea-ice amount, such as the maximum sea-ice extent in the winter season, annual integration of coverage area over ice edge to coast, were not able to explain inter-annual variation of chl a. especially the highest chl a value in 2001/2002. We found a high correlation between the chl a south of 64°S and the sea-ice index, which might be due to the surface meltwater of the sea-ice from the AD zone as a result of eddies. The quantitative relationship might have contributed to the prediction of phytoplankton blooms in this coastal region and demonstrated the impact of the sea-ice extent on the Antarctic marine ecosystem. [ABSTRACT FROM AUTHOR]