The National Mooring Network is a collection of mooring arrays strategically positioned in Australian coastal waters. The National Mooring Network measures physical and biological parameters, and includes regional arrays of shelf moorings, acidification moorings, acoustic observatories and a network of National Reference Stations that include additional vessel-based sampling.
The National Reference Stations deliver long-term time series observations which are critical for defining key components of climate change and associated responses of ocean ecosystems. Currently seven NRS are in operation around Australia (Kangaroo Island, Yongala, Stradbroke Island, Darwin, Maria Island, Port Hacking and Rottnest Island), building on the three long-term locations (Maria Island, Rottnest Island and Port Hacking), where monthly water sampling for physical and biological parameters have been in operation since the 1940’s.
The IMOS shelf moorings are deployed in a wide range of configurations (cross shelf arrays, mooring pairs and single moorings), and are designed to characterise and monitor regional processes on the continental shelf. In some locations, shelf moorings are linked to deep water transport arrays.
Acidification moorings are co-located at some National Reference Station sites to collect the full suite of parameters needed to characterise the concentration of acidification and provide key observations to help us understand and address the problem of increasing ocean acidification.
Acoustic Observatories, which ceased operations in December 2017 passively record sound from the ocean. The data, which is still available via the AODN Portal provide baseline data on ambient oceanic noise, detection of fish and mammal vocalisations linked to ocean productivity and the detection of underwater events.
The National Mooring Network consists of seven different Sub-Facilities.
The National Reference Stations and shelf array moorings are instrumented with a variety of instruments that include acoustic Doppler current profilers (ADCPs), WetLabs Water Quality Meters (WQMs), fluorometers, CTDs with turbidity and dissolved oxygen sensors. Weather stations are also available on the NRS moorings with surface expressions (Maria Island, Darwin, North Stradbroke Island and Yongala). Four of the reference stations (Maria Island, Yongala, North Stradbroke Island and Darwin) relay a reduced data set via Iridium satellite for real time monitoring. All of the moorings have their full data set downloaded at each servicing (approx. 2-4 times a year). Delayed mode data is available within 3 months of being downloaded.
Boat-based water sampling is also undertaken at each of the National Reference Stations on a monthly basis. The vessel based biogeochemical samples include:
- CTD and secchi disk sampling, to ground truth sensor data and other measurements,
- Hydrochemistry and plankton sampling of variables required to monitor nutrients, microbes, phytoplankton and zooplankton (NPZ),
- Water sampling of variables required for carbon monitoring i.e. total dissolved inorganic carbon, total alkalinity, and salinity.
There are also a number of passive acoustic listening arrays comprised by a sea noise logger placed on the ocean floor attached to a mooring which on command, releases floats to the surface. The sea noise loggers were designed and built at Curtin University and are well-proven, fully calibrated instruments. Each mooring also has ancillary temperature loggers attached with one on the seafloor and one between 30-50 m above the seafloor.
Originally, three of the National Reference Stations (Kangaroo Island, Maria Island and Yongala) were equipped with acidification systems. However, the Yongala acidification mooring has now been moved to Heron Island, with Kangaroo and Maria Islands still remaining in place. Each mooring is fitted with surface CO2 systems, using proven and robust technology. Three sensors determine surface CO2, temperature, salinity and oxygen. In addition, the hydrochemistry sampling at the NRS also provide total alkalinity data, while future pH sensors on the moorings will allow for a complete determination of the carbonate system and pH.