HOT-174: Chief Scientist Report
Cruise ID: KM 05-17
Departed: Oct. 6, 2005 at 0900 (HST)
Returned: Oct. 11, 2005 at 0800
Vessel: R/V Kilo Moana
Operator: University of Hawaii
Master of the Vessel: Captain Rick Myer
Chief Scientist: Thomas K. Gregory
STAG Technicians: Gabe Foreman and Tim McGovern
1. SCIENTIFIC OBJECTIVES
The objective of this cruise was to maintain a collection of hydrographic and biogeochemical data at the Hawaii Ocean Time-series (HOT) stations. Four stations were to be occupied during the cruise, in the following order:
1) Station 1, referred to as Station Kahe, is located at 21 20.6'N, 158 16.4'W and was to be occupied on October 6 for about 2 hours.
2) Station 2: ALOHA (A Long Term Oligotrophic Habitat Assessment) is defined as a circle with a 6 nautical mile radius centered at 22 45'N, 158W. This is the main HOT Station and was to be occupied for 3 days.
3) Station 51, is the site of the MOSEAN Mooring, is located at 22º 45'N, 158º 6’W and was to be occupied on the 5th day of the cruise for about 30 minutes.
4) Station 50 is the site of the WHOTS Mooring, is located at 22o 46.1'N, 157o 53.4’W and was to be occupied on the 5th day of the cruise for about 2 hours.
5) Station 6, referred to as Station Kaena, is located off Kaena Point at 21º 50.8'N, 158º 21.8'W and was to be occupied on the 4th day of the cruise for about 2 hours.
A single CTD cast was to be conducted at Station 1 to collect continuous profiles of various physical and chemical parameters. Water samples were to be collected at discrete depths for biogeochemical measurements.
Upon arrival at Station ALOHA, we were to perform CTD casts to collect water for the gas array other experiments and assays. Optics work was to be performed on the second day of the cruise. The 36 hour period was to begin on the third day of the cruise.
Three free-drifting array were to be deployed on this HOT cruise including the gas array, primary productivity array and sediment trap array.
Phytoplankton net tows were to be conducted by C. Mahaffey on several occasions throughout the cruise.
A Profiling Reflectance Radiometer (PRR) was to be deployed for half-hour periods near noon time on three days.
A package including a Wet Labs AC9, a Chelsea Fast Repetition Rate Fluorometer (FRRF), and a SeaBird Seacat was to be used to profile the upper 200 m at Sta. ALOHA on four separate occasions including one nighttime and three daytime casts.
A Ramses optical profiler was to be deployed by L. Stal, J. Huisman and M. Stomp several times during the cruise.
After CTD work at Station ALOHA was accomplished, the ship was to transit to recover the floating sediment trap array. Following this operation, we were to perform CTD casts at both MOSEAN and WHOTS mooring and then transit to Station Kaena.
The following instruments were to collect data throughout the cruise:
shipboard ADCP, thermosalinograph, and two anemometers.
2. SCIENCE PERSONNEL
Chung, Mung Fa
Santiago - Mandujano, Fernando
3. GENERAL SUMMARY
All objectives for HOT 174 were successfully completed. We were able to make use of the extra day given to us to perform experiments not possible within the scope of normal HOT cruises.
4. R/V Kilo Moana, OFFICERS AND CREW, TECHNICAL SUPPORT
The R/V Kilo Moana maintained the excellent ship support for our work we have come to expect from other vessels in the UNOLS fleet. The officers, crew and STAG technicians were most helpful and accommodating. They showed enthusiasm and concern for our work and were very flexible in receiving changes in our operational schedule.
5. DAILY REPORT OF ACTIVITIES (HST)
Oct. 5, 2005; Loading Day
Equipment loaded during this day. CTD wire was re-terminated and CTD
Oct. 6, 2005
The ship departed from Snug harbor at 0900. We arrived at Station Kahe at 1140 and performed a weight cast, Ramses cast, PRR cast and then a 1000 m CTD cast after which we steamed to Station ALOHA.
We arrived at Station ALOHA at 2300 and immediately performed the first gas array cast.
Oct. 7, 2005
We performed three 200 m, one 700 m and three 1000 m CTD casts as scheduled.
The gas array was deployed at 0352
The ATE was deployed at 1025.
The Ramses was deployed at 0938 and 1620.
A PRR cast took place at 1158.
Back to back AC9/FRRF casts occurred at 1240 and 1342.
Oct. 8, 2005
Five 1000 m and one 4800 m CTD casts were conducted on this day.
The first deep cast was started at 0538 and the first 1000 m cast of the 36 hour period began at 1106.
The sediment trap array was deployed at 0124.
The gas array was recovered at 0407 and had drifted southwest.
The Ramses was deployed at 1239.
The PRR was deployed at 1302.
AC9/FRRf casts were conducted at 1335.
October 9, 2005
Seven 1000 m casts were conducted this day. The second deep cast was initiated at 2312
The primary production array was deployed at 0635, was recovered at 1901 and had drifted southwest.
C. Mahaffey performed a net tow at 0039 and 2141.
A Ramses cast was conducted at 1214
Oct. 10, 2005
During the second deep cast, a commercial fishing longline got wrapped around the CTD wire. We successfully recovered the package and freed the longline intact however this complication delayed recovery of the CTD.
One 500 m and one 200 m CTD cast were performed at MOSEAN, one 200 m cast was conducted at WHOTS and one 2500 m CTD cast was performed at Station Kaena.
The sediment trap array was recovered at 0718. The array drifted southwest.
AC9/FRRF casts were conducted at 0340 and 1104.
Oct. 11, 2005
Arrived at Snug Harbor at 0800 and completed a full offload.
Sub component programs:
Bob Bidigare HPLC pigments/UH
Mike Landry Zooplankton dynamics/UH
John Dore CO2 dynamics/UH
Charles Keeling CO2 dynamics and intercalibration/SIO
Mark Abbott/Ricardo Letelier Optical measurements/OSU
Paul Quay DI13C and O isotopes/UW
Penny Chisholm Prochlorococcus population dynamics/MIT
Ancillary research during this cruise:
Claire Mahaffey Assessment of Nitrogen Fixation Rates/UH
Matthew Church Bacterial production and dynamics/UH
Sam Laney Optical characterization of photosynthetic parameters/OSU
Lucas Stal/Jef Huisman/Maayke Stomp Plankton microbiology/optics
John Bullister SF6 and CFC geochemistry/PMEL