Dataset: CTD - DMS and DMSp
Deployment: VDT0410

Refer to SAGE Voyage Report

CTD-related instrumentation consisted of:
- a Seabird Electronics (SBE) 911plus CTD with:
- SBE-5 pumped SBE-3 temperature, SBE-4 conductivity and SBE-43 dissolved oxygen
sensors.
- SBE-5 pumped secondary SBE-3 temperature and SBE-4 conductivity sensors.
- Seapoint Sensors, Inc. SCF chlorophyll fluorometer.
- 25-cm Wetlabs C-star transmissometer.
- Biosherical Instruments Inc. photosynthetic ally active radiation (PAR) sensor, model
QSP200L4S.
- Datasonics sonar altimeter, model PSA-900D.
- a SBE 32 24x10-litre Carousel water sampler.
- Ocean Test Equipment Standard BES external-spring Niskin-type water-sampling bottles.
- Salinity sample bottles.
- CTD winch with 10-km 10.5-mm single-core seacable.

Performance: With the exception of issues noted below, the CTD-related instrumentation apparently
functioned to specification and was operated essentially according to accepted practices for the duration of
the voyage. A total of 85 one-cast CTD stations were completed, labelled u3502 to u3743.

PAR Sensor: The initial CTD PAR sensor experienced an intermittent fault that manifested as a time
variable offset, both cast to cast and, less evidently, within casts. It was eventually replaced with a formally
identical spare unit for station u3719 cast 1 and subsequent casts.

Secondary Conductivity Sensor: The initial secondary conductivity sensor eventually developed a clear
fault (during station u3740 cast 1). It was replaced with a formally identical spare unit for station u3740 cast
1 and subsequent casts. The development of this fault was perhaps somewhat progressive, as possibly
indicated by slight shifts in the primary-secondary conductivity difference on casts before station u3740 cast 1.

Dimethyl sulphide (DMS) and particulate Dimethylsulphoniopropionate (DMSPp)
were quantified by cryogenic-purge-and-trap Gas Chromatography, using a
Pulsed Flame Photometric Detector.

DMS was purged from 20 ml samples that had been gently filtered through
GF/F filters at 5 ml / min using a syringe pump.

DMSPp was quantifed by alkaline hydrolysis to DMS of the particulate material
retained on the GF/F filters.

Calibration was by alkaline hydrolysis of DMSP (98 % purity, CASS,
University of Groningen, NL)