For the second time in 26 months, a large iceberg (C-19) calved off the face of the Ross Ice Shelf. Rather than breaking up, as did its predecessor B-15, the iceberg C-19 remained largely intact, eventually stopping temporarily near Pennell Bank before moving out of the southwestern Ross Sea. The presence of C-19 restricted advection of sea ice out of the region, resulting in unusually high sea ice cover during the spring and summer. Consequently, phytoplankton blooms in the region were diminished dramatically and primary production was reduced by over 90%, relative to normal years. Calving events over the last two decades indicate that reduced primary productivity may be a typical consequence of large icebergs that drift through the southwestern Ross Sea during spring and summer.