Instrumentation

The NRS sampling program involves a high temporal resolution data from a standard, moored sensor package. At sites where surface expression is logistically feasible, surface meteorology and sensor data is delivered in real time. The NRS sampling regime also includes vessel‐based biogeochemical sampling and laboratory analysis.

Moored sensor package

The in-situ moored sensors of the NRS network comprise a number of instruments deployed at all sites that measure a set of core parameters. Additional sensors, identified by the science nodes to collect data for addressing specific science questions, are deployed at a subset of sites.

Schematic representations of the moored sensor design for each of the National Reference Stations. Note, not all instruments are deployed onto single mooring lines. A few modifications have since been done to the moorings: PAR on Maria Island is at 10m, there are no ECO triplets at bottom in Maria and North Stradbroke [90m and 65m]. There is no PAR sensor nor subsurface SBE39s on North Stradbroke. The Ningaloo and Esperance NRS have been decommissioned.

Core parameters

The high temporal resolution data collected at each NRS site are mostly generated by paired - shallow and deep deployed - Water Quality Monitors (WQM; Wetlabs, Philomath, USA) and a bottom mounted Acoustic Doppler Current Profiler (ADCP; Teledyne RDI, Poway, USA). Each WQM consists of a pumped conductivity, temperature and depth (CTD) sampler (SBE MicroCAT, Seabird, Seattle, WA, USA), oxygen sensor (SBE 43, Seabird, Seattle, WA, USA) and a combined flourometer and turbidity sensor (FLNTU; EcoPuk, Wetlabs, Philomath, USA). The fluorescence excitation wavelength of the EcoPuk in the WQM is 470 nm while the emission wavelength is 695 nm. For the turbidity measure the EcoPuk’s wavelength is 700 nm. A variation in instrumentation occurs at Kangaroo Island, where the near surface sensor package consists of a NXIC CTD (Falmouth Scientific, Cataumet, MA, USA) with an Optode oxygen sensor (Aanderraa, Bergen, Norway) and an EcoPuk FLNTU. A Photosynthetically Active Radiation (PAR) sensor (QSP-2100, Biospherical, San Diego, USA) is also mounted on the Kangaroo Island mooring near the FLNTU at 40 m depth.

Water column current velocity and direction are measured using bottom mounted and upward-looking 300 KHz ADCPs at all sites, except Yongala and Darwin, where 600 KHz ADCPs are deployed. These higher frequency ADCPs are better suited to resolving the shallower water and fast tidal patterns of these two sites and are used to infer multi-directional internal waves. ADCPs are deployed either as separate sub-surface moorings (NRS Rottnest, Kangaroo and Port Hacking) or landers (Maria, Yongala, Darwin, North Stradbroke) to avoid interactions with mooring lines. Optical sensors are placed in-line with the mooring wire, as they are designed to take point samples; though the actual sampling volume of the EcoPuks is not characterized by the manufacturer. For the FL signal, interactions with the mooring wire or cage will only occur with fouling as the sensor registers fluorescence. The NTU signal, however, has a greater possibility of wire interactions (Lynch et al 2014).

The NRS Rationale, and Design and Implementation Plan- August 2011 provides a detailed, sound, scientific and operational basis for long term investment in the IMOS National Reference Station (NRS) Network.

Vessel-based biogeochemical sampling and laboratory analysis

Please visit the vessel‐based biogeochemical sampling of NRS for details.

Additional sensors and sampling

In some regions additional sensors or samples are collected. Meteorological data are available for all NRS sites; weather stations (WXT520, Vaisala, Helsinki, Finland) capable of measuring barometric pressure, wind speed, wind direction, air temperature, liquid precipitation and relative humidity along with a surface temperature sensor (SBE 39, Seabird, Seattle, WA, USA) have been deployed in a surface float sensor package at Maria Island, Darwin, Yongala and North Stradbroke Island (summarised in the table below). Complimentary meteorology data are available at the Port Hacking, Kangaroo Island and Rottnest Island sites via Australian Bureau of Meteorology stations located in close proximity to the NRS sites.

Summary of data collected by the surface meteorology stations deployed at the Maria Island (MAI), Darwin, Yongala and North Stradbroke Island (NSI) National Reference Stations

Data stream Units Depth (m)
Barometric pressure hPa -1 and -2 for MAI and NSI
Wind speed m/s -1
Wind direction 0–360° -1
Air temperature °C -1
Liquid precipitation mm -1
Relative Humidity % -1
Sea surface temperature °C 1

Motion reference units (3DMGE1, Microstrain, Williston, USA) capable of recording significant wave height are also deployed at Maria Island and North Stradbroke Island. The NRS also provides capability for the monitoring of carbon dioxide and ocean acidification at the Maria Island and Kangaroo Island sites. Many stations have other, additional sensors which log data to be provided in a delayed mode.

 

REFERENCES:

Lynch, T, Morello, E, Evans, K, Richardson, A, Steinberg, C, Roughan, M, Thompson, P, Middleton, J, Feng, M, Brando, V, Tilbrook, B, Ridgway, K, Allen, S, Doherty, P, Hill, K, Moltmann, T 2014, IMOS National Reference Stations: a continental scaled physical, chemical and biological coastal observing system, PLoS One, vol. 9, no. 12, e113652, doi:10.1371/journal.pone.0113652