Instrumentation

The marine monitoring system is a compact sensor pack (400mmx 150mm x 200mm) that can be mounted horizontally or vertically in a location convenient to the vessel operator. The sampling system was installed in the pump room on the Spirit of Tasmania 1 close to the Seachest water intake (to minimise thermal heating from ship). The antenna-mounted GPS on the vessel roof supplies a digital signal via a shielded cable through the lift shaft to the system some twelve floors below in the pump room.

The in-line system samples in-coming water (via the ship’s cooling system) at 1Hz with a Seabird SBE45 thermo-salinograph (TSG), a Wetlabs combination fluorometer turbidity sensor (FLNTU), and a GPS stream from a 12 parallel channel Leica GPS Smart Antenna.

Digital output from all the instruments are ported to an industrial fanless computer that is set-up alongside the sensor packs in the engine room. Incoming digital data from each sensor is managed via Labview software, and stamped by the PC clock to facilitate melding of data files. Travelling at ~20 knots a 10 second average corresponds to sample “grabs” at every 100m along the ship track. Such high repeat sampling provides an unprecedented capability to monitor ecosystem dynamics down to weather band responses.

The shiptrack is well located to assess dynamics of bay and adjacent ocean exchanges, Bass Strait conditions, upwelling off western Bass Strait and the Mersey Estuary conditions.

Set-up of the autonomous sampling system which utilises the ship's cooling water. Sensors (WET - wetlabs flurometer and turbidity sensor; TSG - themosalinograph) are arranged in-line to minimise sampling delay. Other sensors shown in the figure - an ISUS (SUNA UV nitrate sensor) and ABF (automatic backflushing filter) - not currently on the vessel, will be trialled in 2016.

Twice daily freshwater flushes controlled by a timed manifold, occur while vessel is in port to assist with sensor cleaning. Sensor performance matches the manufacturer specifications indicating the flow stream is not introducing any additional error. Sensor drift is assessed annually with calibration at CSIRO marine laboratories. Additional drift associated with any fouling of the sensors is kept in check with cross-check to standards on every 3-4 week service.