HOT-30: Chief Scientist Report
Chief Scientist: C. WINN
Personnel List
Chris Winn, Chief Scientist
Dale Hebel
Terrence Houlihan
Jef Snyder
Jim Christian
Cheryl McCarthy
Will Hervig
Chris Busing
Terri Rust
Chris Carrillo
Chris Sabine
Ursula Magaard
Hans Thierstein
Soma
Elaine Kotler
Walt
Brian Popp
Omar Carvalio-Martinez
Summary
HOT-30 departed Snug Harbor on the R/V Moana Wave on Monday the 16th of
September at 09:00. Departure was delayed for approximately one hour
due to ship traffic. Both Station Aloha and the Kahe point station
were visited on this cruise. HOT-30 returned to Snug Harbor at 13:00
on Friday the 20th. The sea-state was calm during on the first two
days at Station ALOHA. We noticed that Trichodesmium sp. were
relatively abundant in the upper water column (see below).
WOCE and GOFS Sampling
All chemical sampling was completed on this cruise at both Kahe point
and Station Aloha. The WOCE deep cast was obtained and the WOCE CTD
burst sampling was accomplished without significant problems. The GOFS
sediment trap collections and the GOFS primary production work was also
completed without significant problems. On HOT 30 we divided the
standard GOFS 0 to 1000 decibar sampling into three back-to-back casts
on the first night at Station ALOHA, instead of the usual two. This
strategy worked very well. Using this approach, we were able to hold
to the three hour CTD sampling schedule without difficulty. At the
same time, we were able to collect, process and deploy samples for
primary productivity in between 3 hour CTD casts. I recommend that we
follow this strategy for all future GOFS hydrographic work.
Continuous Profiling
CTD operations also went extremely well on this cruise, and there are
no significant problems to report. The bottom o-rings were changed on
a few of the sampling bottles in order to prevent leaking. In addition
to the regular CTD sampling, the transmissometer was included on most
of the CTD casts. This is third cruise in a row on which
transmissometer profiles were obtained to 1000 decibar. The
Biospherical optical profiler was also deployed at Kahe Point and at
mid-day on all three on the days at Station ALOHA. Typically, least 2
back-to-back light profiles were obtained. On this cruise, the capstan
on main hydrographic winch was used to recover the optical profiler.
The device was deployed as quickly as possible by allowing it to
free-fall. In this way we were able to maximum depth in spite of ship
drift. The package was then recovered at about 20 meters per minute
using the capstan. This was a significant improvement over our usual
hand-over-hand method of obtaining optical profiles. In addition to
being much easier on the science party, this strategy improved data
quality by reaching well below the 0.01% light level, and by obtaining
good resolution on the upcast. I recommend that this strategy be
employed whenever possible on future HOT cruises. The new cage and
mounting system for attaching the transmissometer to the optical
profiler was tested on the last day at station ALOHA. This system
worked well, although the addition of the transmissometer to the
optical profiler makes the package too heavy to recover easily by
hand.
Sediment Trap and Primary Production
The sediment traps were deployed and recovered without serious problems
on HOT-30. The traps drifted approximately 25 kilometers to the
southwest. A new filtration system, on loan from Ed Parnell, was used
on this cruise to filter the sediment trap samples. This pressure
filtration system reduced to time required to process these samples
from the approximately 18 hours on most recent cruises to approximately
8 hours. I recommend that we construct a modified version of this
system for use on future HOT cruises. The primary production
experiment was also successful. However, several light bottles were
lost. This appeared to be due primarily to the poor condition of the
lanyards on the light bottles. I recommend that all of these lanyards
be replaced before the next HOT cruise.
Trichodesmium sp.
During the calm weather encountered on the first two days at Station
Aloha, we noticed an accumulation of Trichodesmium sp. in spherical
colonies at the surface. Net tows were done at several depths above
100 m in an attempt to get some idea of the vertical distribution of
these colonies. In addition, 10 liter samples were collected at
several depths with the rosette sampler. Unfortunately, few colonies
were observed in the 10 liter samples at any depth. Also, opening and
closing nets were not available on this cruise, and the interpretation
of the net tow data is therefore problematic.
Ancillary Work
A number of ancillary projects were supported on HOT-30. A list of
these follows:
Investigator Project Description
------------ -------------------
HOTS Methods Evaluation
a. (T.Houlihan) Evaluation of
freezing for storage of nutrient
samples
b. (D.Hebel) rate of particulate
phosphate dissolution in traps
c. (C.Sabine) rate of calcium
carbonate dissolution in traps
Dr. Dave Keeling Inorganic carbon species in the mixed layer
Dr. Paul Quay Delta 13C samples to 1000 decibars
Dr. Brian Popp DOC sampling using both discrete samples
and sediment traps
Dr. Hans Theirstein Water column sampling for coccolithophores
Dr. Lisa Campbell Picoplankton studies
Dr. Katsumi Phosphorus dynamics
Dr. Omar Calvario Dissolved oxygen as a measure of primary
productivity
Samples for Graduate Students
Soma Krohapalli
Jim Christain
Ricardo Letelier
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