Instrumentation

Southern Australia IMOS moorings typically have RDI workhouse sentinel 300kHz ADCP’s monitoring currents, FSI or Teledyne CTD’s monitoring temperature, pressure and salinity. Additional sensors installed on these CTDs are Wetlabs FLNTU’s (fluorescence and turbidity), Aanderaa oxygen optodes (Dissolved Oxygen) concentration and Biospherical Instruments Inc. PAR sensors (only on NRSKAI mooring).

The SAIMOS national reference station (NRSKAI) mooring is shown in Figure 1. Here the schematic shows the mooring in an upright position as it would in the water column. The mooring components are labelled A, B, C, D…. etc and depths are indicated from the ocean surface.

A The mooring is anchored to the seafloor with one large steel train-wheel (~500kg).

B To create an insulation barrier between metals we use a nylon snatch strap of 9m folded in half (~5m). This is crucial to minimising electrolysis and “sticking” of the release claws.

C Acoustic release units are used to free the mooring from the anchor. We use ORE Coastal Acoustic Release Transponders (CARTs) and as a redundancy, two CARTs are used side by side so that only one is needed to function correctly.

D FSI/Teledyne CTD with FLNTU, DO sensors are configured for hourly sampling over 15secs @ 2Hz without averaging. Instrument nominal depth of ~100m.

E Flotation technologies 32” ADCP float pack with an RDI workhouse sentinel 300kHz ADCP fitted. Velocity sampling is done every 24 seconds (a ping) and then averaged over a 20 minute period and results obtained in vertical bins of 4 m height.

F A 65m plastic jacketed wire cable which holds 12 Aquatec stand-alone loggers. Three are temperature/pressure loggers located at 40 m, 70m, 95 m from the surface and nine are temperature loggers spaced between these every 5m in the water column from ~40-95m. The loggers burst sample for 32 seconds every 20 minutes then averaged.  

G FSI/Teledyne CTD with FLNTU, DO and PAR sensors sampling every hour for 15secs @ 2Hz, without averaging. Instrument nominal depth of ~35-40m.

H Flotation technologies 30” communications float pack with a Xeos Technologies SABLE Iridium satellite tracker and a Siemac Novatech xeon flasher/receiver. These instruments enable us to locate the float packs when recovering or in the case of premature release and recovery.     

The  Southern Australia  regional moorings such as SAM5CB (Coffin Bay) and SAM8SG (Spencer Gulf) are a “cut-down” version of the reference station as shown in the schematic of Figure 2: again depths are indicated from the seafloor. They consist of an anchor pack, nylon snatch strap, tandem ORE CART pack, FSI/Teledyne CTD with FLNTU, DO integrated (sampling configuration as previous), RDI workhorse sentinel ADCP (sampling configuration as previous), and the communications package of the Xeos Technologies SABLE Iridium satellite tracker and a Siemac Novatech xeon flasher/receiver.  

Southern Australia moorings are hot-swapped every 3-6 months to minimise biofouling growth on sensors and to upload data streams. South Australia mooring equipment are calibrated generally every 1-2 years of sea time by the CSIRO calibration facility in Hobart Tasmania. 

Figure 1: NRSKAI- National Reference Station mooring schematic.
Figure 2: SAM8SG- South Australian Spencer Gulf mooring schematic.