HOT-74: Chief Scientist Report

Chief Scientist: F. SANTIAGO-MANDUJANO

            HOT 74 Chief Scientist's Cruise Report
                       R/V Moana Wave
                       25-29 July 1996
                              
                              
Departed: July 25, 1996 at 0900 (HST)
Returned: July 29, 1996 at 0800
Vessel: R/V Moana Wave 
Operator: University of Hawaii 
Chief Scientist: Fernando Santiago-Mandujano 
Master: Captain Robert Hayes 
Deck Operations: Pierluigi Pozzi 
Electronics Technician: Will Hervig                           
                              

1.      SCIENTIFIC OBJECTIVES

The primary objective of the cruise was to maintain the collection of
hydrographic and biogeochemical data at the Hawaii Ocean Time-series
(HOT) station. The HOT station, also known as Station ALOHA (A Long
Term Oligotrophic Habitat Assessment) is defined as a circle with a 6
nautical mile radius centered at 22o45'N, 158oW.  Free-drifting
sediment traps were planned for deployment for approximately 72 hours
from the site to measure sedimentation rates of particulate matter. CTD
casts at three hour intervals were planned to obtain temperature,
salinity, dissolved oxygen and flash fluorescence.  Water samples for
analysis of dissolved nutrients, gases, and biomass were to be
collected with the CTD casts.  Another free-drifting array to conduct a
primary production experiment was planned for a 12 hour deployment. One
other station was planned to be occupied during this cruise; Kahe Point
Station (21o20.6'N, 158o16.4'W). Continuous ADCP as well as
thermosalinograph measurements were to be made during the cruise. Other
research objectives such as the collection of water samples for
ancillary investigations and experiments, as well as the towing of an
optical plankton counter were to be conducted as time permitted.
                             

2.      SCIENCE PERSONNEL

  WOCE group:
     Fernando Santiago-Mandujano    Chief Scientist		UH
     Jefrey Snyder (Watch Leader)   Electronics Technician 	UH
     Molly Lucas           	    Research Assistant		UH
     Craig Nosse               	    Research Associate		UH
     Caroline Dumoulin		    Visiting Graduate Student   UH
     Shaun Johnston                 Graduate Student      	UH

  JGOFS group:
     Dale Hebel	(Watch Leader)	    Scientist (co-PI JGOFS) 	UH
     Lance Fujieki            	    Computer Specialist		UH
     Terry Houlihan      	    Research Associate		UH
     Daniel Sadler            	    Graduate Student       	UH
     Scott Nunnery	      	    Student			UH
     Hussain Al-Mutairi             Graduate Student		UH - M. Landry

  Ancillary projects
     Mai Lopez		      	    Scientist			SIO - M. Huntley
     Bill Cottrell	      	    Electronics Thechnician	Ashtech
     Jeffrey Milder           	    REU Student			UH - B. Popp

  STAG
       Will Hervig                  Technician			UH-UMC
       Pierluigi Pozzi         	    Technician			UH-UMC


3.      GENERAL SUMMARY

All the primary JGOFS and WOCE objectives were accomplished and all
samples for ancillary projects were taken. Weather conditions were very
favorable during the cruise. This allowed for a safe deployment and
recovery of the floating sediment traps, the deployment and recovery of
the primary production array and of the Go-flo hydrocast, the
completion of the 36-hour CTD burst sampling including two deep casts;
and the towing of the optical plankton counter-CTD package in a zig-zag
trajectory within the ALOHA circle.  Four of the eight bottles in the
Go-flo hydrocast did not close properly, consequently water from the
CTD cast had to be used for some of the bottles in the primary
productivity array.  The OPC had to be retrieved earlier than planned
given that problems with the ship's engine would not allow us to
achieve full speed in the way back to Honolulu. A total of eight
plankton net tows were completed during the cruise, although two of
them did not sample correctly due to problems during deployment.

The ADCP ran without interruption throughout the cruise, and was set to
bottom track when the bottom depth was appropriate at the beginning and
the near the end of the cruise. Bill Cottrell (Ashtech) collected test
data with his GPS and the ship's Ashtech GPS during the cruise. The
thermosalinograph worked continuously throughout the cruise. On the
second day Will Hervig noticed high temperatures in the external
temperature sensor data, which went back to normal after reseting the
system. A preliminary look at the data shortly after the cruise
indicated that the system malfunctioned and did not record data for
about 5 hours before the end of the cruise.
 
We arrived at Snug Harbor on July 29 at 0730 and immediately
off-loaded, however the majority of the deck and lab equipment remained
onboard for the next cruise.


4.      R/V MOANA WAVE, OFFICERS AND CREW, TECHNICAL SUPPORT

The R/V Moana Wave continues to maintain the excellent ship support for
our work. The officers and crew were most helpful and were very
flexible in receiving changes in our operational schedule.  Technical
support during the cruise was also very good. STAG personnel were
available at any time to assist in our work.


5.      DAILY REPORT OF ACTIVITIES (HST)

July 24, 1996; Loading Day

All equipment was loaded from Snug Harbor labs and UH. All electrical
connections for the CTD and OPC were made and tested.  Niskin bottles
caps were assembled and checked. All instruments were installed,
secured and tested. No problems were encountered.


July 25, 1996.

Ship departed at 0900. Fire and emergency drills conducted by the first
mate at 1000. A short science personnel meeting followed in which the
schedule of activities was reviewed and safety measures were stressed
out. Thermosalinograph and ADCP working correctly. A 1000 m weight cast
was conducted at 1145 upon arrival at Kahe Station, followed by a 150-m
Profiler Reflectance Radiometer (PRR) cast at 1230.  At 1300 a 1000-m
CTD cast was conducted, after which we departed to the ALOHA Station.
We arrived at ALOHA Station at about 2230 and started preparations for
the floating sediment trap deployment.

The winds at Kahe Pt. were very light, less than 10 kt from the
southwest.  They reversed to easterlies and increased to about 15 kt
after the ship passed Kaena Pt. at about 1600 in the transect to
Station ALOHA.

July 26, 1996.

A floating array with two sediment traps was deployed by 0000, followed
by a 30-min plankton net tow at 0100. Due to problems during deployment
this tow did not collect material appropriately and had to be
discharged. The WOCE deep cast started at 0315 and was completed at
0640, the altimeter did not work during this cast, so the pinger's
signal was used to determine the distance between the CTD and the
bottom. Samples from the IES were observed on the 12 Khz recorder
during this cast. One PRR profile was done at 1200. Two 30-min plankton
net tows were done during the day (1030 and 1330) and one more at night
(2200). The 1330 net tow did not collect enough material as apparently
the net turned over during deployment.

 The 36-hour period started with the WOCE shallow cast at 0800, and by
the end of the day a total of six (6) 1000-m CTD casts had been
completed at station ALOHA. At about 1500, W. Hervig found that the
thermosalinograph external temperature sensor was recording very high
temperatures. The temperatures came back to normal after reseting the
system at 1535.

Weather conditions were favorable. Winds from the east at 15 kt, and
seas of 1-2 ft.


July 27, 1996.

Operations at station ALOHA continued as planned. The Go-flo hydrocast
was deployed between 0100 and 0230. Four of the bottles did not close
properly during this cast due to problems with the lanyards that had
been replaced before the cruise.  Consequently, water from the CTD cast
Niskin bottles had to be used for some of the bottles in the primary
productivity array. The primary productivity array was deployed without
difficulty at 0430 and was retrieved at 1900. Two net tows were
conducted at night at 0000 and 2200, and two during the day at 1000 and
1300. A PRR profile was obtained at 1200.  Eight (8) CTD casts were
completed during this day, making a total of 15 at the ALOHA station.
The sediment traps ARGOS positions were received by e-mail and
plotted.  By 0620 the sediment traps array had drifted about 10 nm
northeast from the ALOHA station.

Weather conditions continued being favorable. Winds were from the east
at 10 kt, increasing to 15-20 kt during the last 10 hrs of the day.
Seas were about 2-4 ft.


July 28, 1996.

Two more CTD casts were completed during the last day of the cruise.
The first one was to 1000 m and the second was a deep cast. Again, the
altimeter did not function during the deep cast.

The sediment traps drifted about 15 nm northeast from the ALOHA
Station. The array was retrieved without difficulty between 1200 and
1240. The OPC was deployed at 1340 and retrieved at 1830 after
following a zig-zag trajectory within the circle. The OPC had to be
retrieved earlier than planned given that problems with the ship's
engine would not allow us to achieve full speed in the way back to
Honolulu.

Weather was favorable with easterly winds of 15-20 kt and seas 3-4 ft
high.

July 29, 1996.

Arrived at Snug Harbor at 0730. Proceeded with unloading, however the
majority of the deck and lab equipment remained onboard for the next
cruise. Unloading completed by 1100.


ANCILLARY INVESTIGATIONS AND SPECIAL PROJECTS

M. Lopez		Optical Plankton counter
H. Al-Mutairi		Zooplankton dynamics
D. Sadler		DIC sampling
J. Milder		Carbon Isotopic Fractionation
B. Cottrell		Ashtech GPS


SAMPLES TAKEN FOR OTHER INVESTIGATORS

C. D. Keeling 		CO2 isotopes
P. Quay 		CO2 measurement
H. Thierstein 		Microscopy