Situation Report, NB Palmer Cruise 96-4A;    October 30, 1996


     The R.V. NB Palmer  continued its investigations into the early
spring carbon dynamics of the southern Ross Sea.  As part of this
investigation, measurements of phytoplankton biomass and productivity,
bacterial biomass and productivity, and meso- and microzooplankton
biomass and growth are being made, in conjunction with the
determination of nutrient concentrations, water column structure, trace
metal levels, and thorium-particle interactions.  During this past week
we completed a long station at our coastal site (Minke), transited to
our open water site (Orca) and completed a long (24 h) station at that
location, and then moved closer to the Ross Ice Shelf.  The purpose of
this was two-fold.  First, we had hoped to sample ice-free waters,
something which we had been unable to do previously (and thus contrast
the photophysiology of a phytoplankton assemblage exposed to continuous
light vs. those growing under ice cover, and contrast the resultant
carbon dynamics), and second, we hoped to assess the contribution of
"warm" (ca. -1  deg. C) waters upwelled from off the continental shelf
to the opening of the polynya (and to measure the trace metal
concentrations in this water).  We then returned to Orca for additional
work (as part of a long-term time series at this location).

     We have consistently encountered "winter" conditions (i.e., those
not favorable to phytoplankton growth).  Mixed layers, as evidenced by
density profiles, have been deep and reached over 600 m at  some
locations.  These deep mixed layers were not accompanied by strong
winds.  All sites were ice-covered, although the ice at Orca was
thinner (ca.  40 cm) than that at Minke (ca. 150 cm).  The ice-shelf
station was also ice- covered; however, the ice was thin and still
forming under the influence of off-shelf winds (air temperatures
dropped to -32 deg. C at this location).  The mixed layer at this depth
was ca. 500 m, and no trace of off-shelf water was detected.
Chlorophyll levels were low (ca. 0.1 ug/l), primary productivity low
(approximately 0.1 gC/m2/d), bacterial biomass and production low,
nutrient levels high, and carbon dioxide concentrations high and
invariant (ca. 430 ppm).  We have preliminary evidence that at Orca a
phytoplankton bloom is beginning; chlorophyll levels are increasing
slightly, microscopic evidence shows an increased number of cells and
colonies, and pCO2 levels dropped.  We hope that at our return to this
site that we will collect further evidence of the bloom's onset.

     We also conducted are iron intercomparison.  Samples for trace
metals were collected by the Moss Landing group from the CTD rosette,
the trace metal clean rosette, and from  the MLML go-flo bottles at the
same depth.  Samples will be analyzed by both the MLML group (K.
Coale) and by C. Measures (Hawaii).

     Despite difficult conditions encountered during early spring, we
believe we have collected the first data to assess the carbon dynamics
during the onset of the seasonal phytoplankton bloom in the Ross Sea.
During the last week of the cruise we will re-occupy site Minke,
transit back to Orca, and re-occupy all the stations along the 76 deg.
30 min. S transect before disembarking at the ice edge near McMurdo
Station.  We look forward to a busy and productive week.

Submitted:     Walker Smith, Chief Scientist