Within the Australian marine system, geographically comprehensive long-term monitoring programs are challenging given the large size of the Nation’s ocean territory and extensive continental coastline. To address a general lack of sustained ocean observations essential for documenting long term time-series against which more spatially replicated short term studies can be referenced, IMOS in collaboration with marine institutional partners developed a network of National Reference Stations. The National Reference Station Network is designed to provide baseline information that is required to understand how large‐scale, long-term change and variability in the global ocean are affecting the ecosystems of Australia's coastal seas. The goal is to develop multi-decadal time series of the physical and biogeochemical properties of Australia’s coastal seas, to inform research into ocean change, climate variability, ocean circulation and ecosystem responses. Traditionally, monitoring has been undertaken by regular boat-based sampling at simple waypoints. Through the IMOS National Reference Station Network, moored instruments are now located at three historical long-term sites and four additional sites around Australia’s coast, allowing fine scale temporal investigation of a number of variables.
Deployed in up to 100m of water, the moorings record data about the physical and biological properties of the water such as fluorescence and dissolved oxygen concentration, with some moorings also collecting meteorological data. Observations at the National Reference Stations are undertaken through the water column, from surface to seabed and are sensor-based, where possible, and supplemented by vessel-based biogeochemical sampling. Configuration of the moorings at each station is modified regionally to cope with local deployment challenges from fish bite to cyclones.
The National Reference Stations collect observations of both physical and biogeochemical variables to characterise the ocean environment and to understand fundamental biological processes within the environment. Core physical variables observed include temperature, salinity, dissolved oxygen, nutrients, turbidity, carbon, phytoplankton (both direct, and via an optical proxy for chlorophyll a), and zooplankton.
Understanding these variables necessitates observations at NRS sites being undertaken through the water column, from surface to seabed. Observations are sensor‐based and supplemented by vessel‐based biogeochemical sampling (and laboratory analysis) at minimum frequencies required to provide appropriate resolution for core variables.
As the resources required to sustain physical and biogeochemical observations over the long term are significant, the NRS Network consists of the minimum number of sites necessary to provide a national multi‐decadal baseline. At these timescales, ocean processes are operating at space scales in the thousands of square kilometres, and the IMOS NRS is hence a sparse network of well‐ instrumented, single‐point, reference sites, strategically positioned around Australia’s coastline.