Abstract:

The investigation of chlorophyll a and primary productivity were carried out in three longitudinal sections (70°30′E, 73°00′E and 75°30′E) at December 18-26,1998 and January 12 -18, 1999 in Prydz Bay and its north sea area. The results showed that surface chlorophyll a concentration were 0.16-3.99 μg/dm 3 . The high value of chlorophyll a concentration (more than 3.5 μg/dm 3 ) was in the bay and West Four Ladies Bank. The average chlorophyll a concentration at sub surface layer (25m) was higher than that at surface layer; its concentration at the deeper layers of over 50m decreased with increasing depth and that at 200m depth was only 0.01-0.95 μg/dm 3 . The results of size frationated chlorophyll a showed that the average contribution of netplankton to total chlorophyll a in surveyed area was 56%, those of nanoplankton and picoplankton were 24% and 20% respectively. The potential primary productivity at euphotic layer in investigated area was 0.11-11.67mgC/(m 3 ·h) and average value was 2.00±2.80 mgC/(m 3 ·h). The in situ productivity in the bay and continental shelf was higher and that in deep sea area was lower. The assimilation number of photosynthesis was 1.53±1.11 mgC/(mg Chl a ·h). The results of size frationated primary productivity showed that the average contribution of netplankton to total productivity in surveyed area was 58%, those of nanoplankton and picoplankton were 26% and 16% respectively. The cell abundance of phytoplankton was 1.6×10 3 -164.8×10 3 cell/dm 3 .